Norcross Wildlife Foundation, Bexley City School District

Transcription

1 REPORT ON THE 2008 GREEN TURTLE PROGRAM AT TORTUGUERO, COSTA RICA Submitted to Caribbean Conservation Corporation and the Ministry of Environment, Energy and Telecommunications of Costa Rica 31 July, 2009 by Dagnia Nolasco del Aguila, Field Coordinator Xavier Debade, Field Coordinator Dr Emma Harrison, Scientific Director Inocencio Abrego, Research Assistant Jose Alonzo Torres, Research Assistant Geiner Alvarado Ramirez, Research Assitant Sarah Amri, Research Assistant Jesus Cortez Solano, Research Assistant Oscar Cañon Gonzalez, Research Assistant Donnel Dulay, Research Assistant Karla Evangelista Reyes, Research Assistant Luis Gonzalez, Research Assistant Catalina González Príeto, Research Assistant Jorge Gonzalez Villalba, Research Assistant Christine Honan, Research Assistant With assistance from Christine Lillie, Research Assistant Georgina Mariona Castillo, Research Assistant Eliseo Moran, Research Assistant Julia Nelson, Research Assistant Adhith Swaminathan, Research Assistant Armando Villagra, Research Assistant Carlos Villalobos Martinez, Research Assistant Apanie Wood, Research Assistant Alex Zalewski, Research Assistant Ruddy Gonzalez, Track Surveyor César Gamboa Ruiz, Track Surveyor Jorge Ivan Ramos, Track Surveyor With financial support from: Bay & Paul Foundation, The Lemmon Foundation, Norcross Wildlife Foundation, Bexley City School District Address: Apartado Postal NW 13 th St. Suite B-11 San Pedro Gainesville, FL COSTA RICA USA Phone: INT INT Fax: INT INT emma@cccturtle.org ccc@cccturtle.org Webpage:

2 Table of Contents TABLE OF CONTENTS... I LIST OF TABLES...II LIST OF FIGURES...II ACKNOWLEDGMENTS...1 EXECUTIVE SUMMARY...2 Monitoring and Research Activities Conducted...2 Conclusions...5 Recommendations INTRODUCTION METHODS Preparations Track Surveys Tagging of Nesting Sea Turtles Biometric Data Collection Fibropapilloma Assessment Determination of Nest Survivorship and Hatching Success Physical Data Collection Collection of Human Impact Data Environmental Education and Outreach Activities Independent Research Projects RESULTS Preparations Track Surveys Tagging of Nesting Sea Turtles Biometric Data Collection Fibropapilloma Assessment Determination of Nest Survivorship and Hatching Success Physical Data Collection Collection of Human Impact Data Environmental Education and Community Outreach Activities Independent Research Projects DISCUSSION Preparations Track Surveys Tagging of Nesting Sea Turtles Biometric Data Collection Fibropapilloma Assessment Determination of Nest Survivorship and Hatching Success Physical Data Collection Collection of Human Impact Data Environmental Education and Community Outreach Activities Independent Research Projects REFERENCES APPENDICES...60 I

3 List of Tables Table 1. Probability of within-season tag loss from first-to-last encounter Table 2. Mean carapace length and clutch size of green turtles Table 3. Precision of carapace measurements for green turtle females Table 4. Mean carapace length of hawksbill females Table 5. Precision of carapace measurements for hawksbill females Table 6. Mean carapace length of leatherbacks Table 7. Fate, hatching and emerging success of marked green turtle nests in Table 8. Summary of excavation data for green turtle nests marked in Table 9. Incidence of albinism, twins and deformed embryos in Table 10. Summary of hawksbill nest excavations from Table 11. Summary of rainfall data March to November, Table 12. Summary of air temperature data March to November, Table 13. Mean monthly sand temperatures during the 2008 Green Turtle Program Table 14. Number of visitors to the CCC Natural History and Visitors Center Table 15. Number of paying visitors to Tortuguero National Park, Table 16. Room and bed capacity of the hotels and cabinas in the Tortuguero area Table 17. Number of visitors participating in turtle tours in Table 18. Turtle hatchling orientation observed during the 2008 Green Turtle Program Table 19. Hatchling disorientation observed during the 2008 Green Turtle Program Table 20. Summary of environmental education activities conducted during the 2008 Green Turtle Program Table 21. Duration of different phases of the nesting process for turtles subject to different levels of tourism impact List of Figures Figure 1. Temporal distribution of green turtle nesting at Tortuguero in 2008, as determined from weekly track surveys Figure 2. Green turtle nesting trend at Tortuguero, , as determined by weekly track surveys of the entire beach Figure 3. Spatial distribution of green turtle nesting at Tortuguero in 2008, as determined from weekly track surveys Figure 4. Leatherback nesting trend at Tortuguero, , as determined by weekly track surveys Figure 5. Results of daily track surveys of the northern 5 2/8 miles of beach in Figure 6. Illegal take of green turtle nests and females in 2008, as determined from daily track surveys of the northern 5 2/8 miles of beach Figure 7. Mean monthly sand temperatures from June - October Figure 8. Summary of monthly light surveys conducted during the 2008 Green Turtle Program II

4 Acknowledgments The 2008 Green Turtle Program was conducted under a research permit from the Tortuguero Conservation Area of the Ministry of Environment and Energy of Costa Rica, detailed in resolution N o ACTo-GASP-PIN Tissue samples were collected in accordance with the collection permit N o R OT-CONAGEBIO issued by the National Commission for the Management of Biodiversity (CONAGEBio). This report was made possible thanks to the dedication of the 2008 Green Turtle Program research team; all the data presented here were collected by Field Coordinators (FC) Xavier Debade and Dagnia Nolasco, and the dedicated team of Research Assistants (RA): Inocencio Abregoo (Panama)Jose Alonzo Torres (Costa Rica), Geiner Alvarado Ramirez (Costa Rica), Sarah Amri (USA), Oscar Cañon Gonzalez (Colombia),, Donnel Dulay (USA), Karla Evangelista Reyes (El Salvador), Luis Gonzalez (Spain), Catalina González Príeto (Colombia), Jorge Gonzalez Villalba (Mexico), Christine Honan (USA), Christine Lillie (UK), Georgina Mariona Castillo (El Salvador), Eliseo Moran (Panama), Julia Nelson (USA), Adhith Swaminathan (India), Armando Villagra (Panama), Carlos Villalobos Martinez (Mexico), Apanie Wood (Australia), Alex Zalewski (France). In addition, many volunteer participants aided in data collection throughout the Program, and we gratefully acknowledge their assistance. The weekly track surveys of the entire beach were conducted by Ruddy Gonzalez, César Gamboa Ruiz and Jorge Ivan Ramos, whose considerable efforts we very much applaud. The hard work of all the John H. Phipps Biological Station staff was crucial to the success of the 2008 Green Turtle Program. Station managers Sergio Campos and Juan Carlos Cordero supervised the running of the station; Marisela Estrada and César Gamboa Ruiz administrated the visitor center; boat captain Jorge Bustos safely transported researchers on the canals; Zelmira Williams made sure that everyone was well fed; Jeanette Molina and Marta Rivas were responsible for keeping the station clean and ensuring that everyone had clean clothes; and the station was kept secure, day and night, by security personnel José Lara and Wilfredo Davila. Mr. Eduardo Chamorro and the dedicated park rangers of the Tortuguero Conservation Area (ACTo) are due acknowledgement for their on-going efforts in reducing threats to sea turtles in Tortuguero National Park and surrounding areas. Also, the assistance of the park rangers, the Tortuguero Tour Guide Association and personnel of the Turtle Spotter Program, especially coordinator Andrea de Haro, in helping to maintain a controlled tourist presence on the beach is much appreciated. In addition, the CCC would like to acknowledge the residents of Tortuguero, in particular Enrique Obando, for their continued support throughout the 2008 Green Turtle Program. Our outmost gratitude is extended to National Director Roxana Silman and her assistant Maria Laura Castro in San José, who provided complete logistical support throughout the Program. The help of CCC staff based in the Gainesville, Florida office is also recognized. For financial assistance we would like to thank the Bay & Paul Foundation, Bexley City School District, the Lemmon Foundation, the Marisla Foundation, the Norcross Wildlife Foundation and all the 2008 Green Turtle Program participants. 1

5 Executive Summary Monitoring and Research Activities Conducted 1 During 2008, a total of 49 track surveys were conducted along the entire 18 miles of beach between Tortuguero river mouth and Jalova lagoon. 2 Green turtle nesting was observed between February and November, 2008; with the first nest recorded on 3 February. 3 Peak nesting was recorded on 30 August, 2,243 nests were counted in a single night. 4 An estimated 107,852 green turtle nests were laid during A total of 17.4% of all green turtle nests recorded during track surveys were deposited between Tortuguero river mouth (mile 3/8) and mile 5, where all night patrols took place. 6 Jaguars killed a minimum of 23 green and one hawksbill turtle in 2008; on two occasions in September five turtles were killed in a single night. 7 Hawksbill nesting density was very low throughout the season, with six nests recorded in May and June; on 7 June three hawksbill nests were counted from one night. 8 During daily track surveys conducted by RAs between 14 June and 1 November and a total of green turtle nests and 17,348 green turtle false crawls were recorded between the Tortuguero river mouth and the mile 5 marker. 9 Nine leatherback and 21 hawksbill nests were recorded green turtles and 276 nests were recorded as poached during daily track surveys. One leatherback and one hawksbill nest were also taken. 11 Illegal poaching activity was observed on 72.1% of surveys green turtle nests were depredated by dogs; the majority were close to the village. 13 2,065 team hours of night patrols were conducted from 12 June 30 October. 14 A total of 1,367 green turtles were newly tagged, 524 green turtles with tags from previous years and 482 renesters were encountered during night patrols of the previously tagged turtles had been originally tagged more than 10 years ago and seven more than 20 years ago. 16 Two turtles were first tagged in 1980, which is a new nesting history record for the project of 28 years. 17 Twenty-two green turtles from other projects were encountered nesting at Tortuguero in 2008; two were tagged on the beach in Pacuare Nature Reserve, seven were from Mondonguillo, three were from Parismina and 10 were tagged by researchers from Caño Palma, north of the Tortuguero river mouth. 18 Two green turtles were originally tagged in Panama; one at Soropta Beach in 2005 and the other at Chiriquí Beach in

6 19 One turtle had originally been tagged in feeding grounds off the coast of Cuba in Overall probability of within-season tag loss from first to last encounter was high at 6.8%, and there was considerable variation between taggers and between months. 21 Newly tagged green turtles had evidence of old tag holes or notches in at least one front flipper in 14.2% of cases. 22 Tagging efficiency for night patrols varied from 0-44%, with a mean of 6.7%, for nights preceding track surveys. 23 Green turtles encountered during night patrols nested in the open zone in 18.8% of cases (n = 445), 72.3% (n = 1,710) were located in the border zone and 5.8% (n = 137) in the vegetation zone. 3.0% of turtles were encountered during a false crawl emergence (n = 72). 24 Eight newly tagged and three previously tagged hawksbill turtles were encountered during the 2008 Green Turtle Program; two of these females were observed twice during the season. 25 All hawksbills nested successfully; two nests were laid in the open zone, nine nested in the border zone, and two nested in the vegetation zone. 26 Four leatherback turtles were encountered during the 2008 Green Turtle Program; one was a new recruit, one was previously tagged in Tortuguero in 1996 and two were females that had been seen during the 2008 Leatherback Program. 27 Overall carapace length for green turtles was cm (CCLmin) and 99.0cm (SCLmax). 28 Mean clutch size for green turtles was 111 eggs. 29 Measurement precision of green turtles was the same for CCLmin than for SCLmax within a single encounter; 0.3cm. For turtles encountered two to five times, the SCLmax measurements were more precise. 30 Mean carapace length for hawksbill turtles was 85.3cm (CCLmin) and 81.6cm (SCLmax). 31 Mean clutch size for hawksbill females was 152 eggs. 32 Mean carapace length of leatherbacks was 152.2cm (CCLmin). 33 Mean clutch size for leatherbacks was 61 yolked and 41 yolkless eggs. 34 Of 192 green turtles carefully examined for the presence of fibropapilloma tumors only three were recorded with tumors (1.6%). An additional seven females encountered were found to have tumors present; these ranged in size from 1-7cm and were typically located on the front flippers or the neck area. 35 A total of 145 green turtle nests were marked and the fate was determined for 134 nests. Overall mean hatching success is estimated at 84.1% and overall mean emerging success at 80.7%. 36 The biggest cause of nest loss was poaching 13.4% (n = 18), while other females partly dug up eight nests (5.9%) and a further three nests (2.2%) were partly poached. 37 Comparison between egg counts at excavation and the moment of oviposition showed a mean difference of 4.3 less eggs counted at the time of the excavation. 3

7 38 Mean depth for undisturbed green turtle nests (n = 99) at excavation was 56.9cm from the sand surface to the top egg and 72.7cm to the bottom of the egg chamber. 39 The mean incubation period for undisturbed green turtle nests where hatching was observed (n = 66) was 57 days. 40 A total of four albino, one set of twins and 25 deformed embryos were observed in unhatched eggs, accounting for 0.25% of eggs. 41 Five hawksbill nests were monitored and their fate determined; all were undisturbed. 42 Hatching success of hawksbill nests (n = 5) was 77.9% and emerging success was 50.9%. Two nests with large numbers of hatchlings inside were the reason for the reduced emerging success. 43 Mean incubation period for hawksbills nests was 59 days (n = 3). 44 Mean depth to top egg for hawksbill nests was 42.0cm and to the bottom of the egg chamber was 56.2cm. 45 Rainfall was monitored from March - November 2008; November was the wettest month (885.6mm) and September was the month with least rain (145.3 mm). 46 Mean minimum air temperature was lowest in November (22.3 C); mean maximum air temperature was highest in April (29.0 C). 47 Mean monthly sand temperatures ranged from C. For all depths, temperatures were highest in the open zone. 48 Problems were encountered with the data loggers and no data were collected after 15 October, A total of 29,536 persons visited the CCC Natural History and Visitors Center in 2008, a decrease of around 500 people from numbers recorded in Tourist visitation to Tortuguero National Park (TNP) increased significantly in 2008, to 134,690 paying visitors. Entrance fees to TNP generated a total of 455,051,638 (~ US$777,202). 51 The capacity of hotels and cabinas in the Tortuguero available to tourists increased slightly in 2008 to 675 rooms and to 1,519 beds. 52 A total of 47,510 tourists were issued permits to go on guided turtle tours in 2008; an average of 334 tourists per night during the green turtle season (July - October). The peak in tourist activity was on 6 August when 768 people participated in turtle tours. 53 The new funding initiative that was implemented for the Turtle Spotter Program continued in % of tourists supported the program, raising $104,344 which completely cover all the program expenses. Funds from 2007 were used to construct two new tourist waiting areas prior to the start of the 2008 season. 54 Artificial lights from houses, shops and cabinas are still a problem on the beach in front of Tortuguero village. In addition, lights are also visible from the lodges north of the village, and from San Francisco, close to the river mouth. 55 The angular range of hatchlings crawling from nests was determined for 44 nests; 33 green turtle, 11 leatherback and 1 hawksbill. The mean angular range was 18.5, 14.5 and 22.0, respectively, 4

8 if outliers were excluded. If outliers were included the values were 41.5, 42.5 and 39.0, respectively. 56 On 12 occasions evidence of hatchling disorientation caused by artificial lighting behind the beach was observed; on all occasions the hatchlings eventually made their way to the sea. 57 A coordinated environmental education program was carried out during the 2008 Green Turtle Program for students of the education establishments in Tortuguero and San Francisco. The theme chosen for the program was Flora and Fauna of Tortuguero, and 12 activities were developed that related to this theme. 58 A new education program was developed for students of Tortuguero high school; the Junior Research Assistant Program. Students undertook a series of different practical and theoretical assignments. Five students completed all the requirements to graduate from the course. 59 The second veterinary spay/neuter clinic was conducted June; 63 animals were castrated and 61 received vaccinations. 60 Two independent research projects were conducted during the 2008 Green Turtle Program both relating to the impact of tourism on green turtles; one investigated the effect of tourists on the nesting behavior of females and the other studied the impact of trampling on nesting and emerging success. Conclusions 1 The pattern of green turtle nesting was similar in 2008 to that observed in previous years, with most nesting occurring between July and October, and peaking in late August. 2 Daily track surveys provide detailed information about the illegal take of green turtle females and nests; levels observed in 2008 were higher than in The record for the longest history of green turtle females nesting at Tortuguero is 28 years. 4 Cooperation between researchers working at sea turtle projects around the Caribbean allows interesting tag returns to be identified, such as the females with tags from Cuba and Panama observed during the 2008 Green Turtle Program. 5 Within-season tag loss was high (6.8%) in 2008; this highlights the need to ensure that RAs receive adequate training and supervision while tagging during the first few weeks of night patrols. 6 Fibropapilloma infection remains low within the Tortuguero green turtle population. 7 Environmental data collected at Tortuguero each year provide important baseline data on changes in rainfall, air temperature and sand temperature over the last 10 years. 8 Tourist visitation to Tortuguero National Park continues to increase each year. 9 The new Junior Research Assistant Program helped to stimulate the high school students to get involved in CCC activities; it also provided an opportunity for the FCs and RAs to develop closer ties to the community. 10 Independent research projects studying the effects of tourism on green turtles revealed important findings that will allow effective management of the Turtle Spotter Program to minimize negative impacts of effects tourism. 5

9 Recommendations 1 The new extended RA training and orientation program should be continued in future years as it gives RAs a more in-depth introduction to Tortuguero and the National Park, and provided more opportunity for group interactions during the first few weeks. 2 Adequate training of RAs in all aspects of the monitoring protocol is essential to ensure that they are tagging and collecting data effectively and accurately; increased practical sessions in tagging, carapace measurements and nest marking should be scheduled during the orientation period, with on-going supervision throughout the program. A bilingual training video would be a useful tool to provide RAs with detailed visual instruction on how to perform all aspects of the monitoring protocol 3 The weekly track surveys are vital for the continued evaluation of long-term trends of turtle populations at Tortuguero; care should be taken when selecting and training a new surveyor to ensure that they are able to correctly identify different species, that they can distinguish between a nesting and non-nesting emergence, and that they can recognize signs of illegal take of eggs or turtles and jaguar predation. 4 It is important that all data regarding illegal take of turtles and nests be provided to the relevant enforcement authorities. It would be advisable to inform not only the Ministry of Environment and Energy, but also the Coast Guard, to ensure adequate patrols both on land (to protect nesting females) and at sea (to protect males and females in near-shore waters). 5 There is a continued need for increased coordination and data exchange between sea turtle conservation and monitoring projects being conducted throughout the Caribbean. 6 The veterinary clinics should be continued in future years and CCC should remain involved in the committee organizing the campaign to try and reduce the number of dogs in the community. 7 Collection of physical data should continue on a daily basis throughout the year, to monitor changes in environmental conditions in Tortuguero and provide a baseline for possible studies into the effects of climate change on sea turtles and their habitats. 8 The Turtle Spotter Program should continue in future years and CCC should remain responsible for the evaluation of the program activities. Further studies should be conducted to investigate potential negative impacts on nesting turtles and their nests. It is important that CCC remains an integral part of the committee responsible for overseeing the development and implementation of the program activities. 9 The Costa Rican electricity company should be approached regarding the situation with the public lighting in Tortuguero; to develop a method in which lights visible on the beach could be shaded during the nesting and hatching season. Furthermore, a campaign should be organized to raise awareness within the communities of Tortuguero and San Francisco of the negative impact caused by artificial lights to turtles and hatchlings. 10 A structured program of environmental education activities within the community should be continued, and further developed to encompass a broader section of the population, not just the children. Efforts should be made for CCC to become more integrated with the community; to provide information about the work of CCC in the region and to invite interested persons to participate in the monitoring activities. One key focus group would be the women of Tortuguero. The practice of employing two FCs, one focused on community involvement, should be continued. 6

10 1. Introduction Dr. Archie Carr began studies of green turtles (Chelonia mydas) in Tortuguero in 1954 (Carr et al. 1978). Since 1959, the Caribbean Conservation Corporation (CCC) has implemented the annual Green Turtle Program. Prior to the 1998 nesting season, CCC staff and the Scientific Advisory Committee revised the Green Turtle Program monitoring protocol. The new protocol defines that the Green Turtle Program is conducted in order to fulfill CCC s scientific mission in Tortuguero: CCC will provide the scientific information necessary to conserve the populations of sea turtles that nest at Tortuguero, Costa Rica, so that they fulfill their ecological roles The 2008 Green Turtle Program represents the eleventh consecutive year of implementing the revised monitoring protocol. The objectives of this report are to summarize and discuss the results of the 2008 Green Turtle Program and provide recommendations for future sea turtle programs, conservation efforts and research activities in Tortuguero. 2. Methods 2.1 Preparations At the start of the 2008 Green Turtle Program the RAs completed an extensive orientation and training program; they received lectures about sea turtle biology and conservation, and the Green Turtle Program monitoring protocol was explained in detail. The RAs were also introduced to key members of the community, including staff at the National Park ranger station. They learned about the history of the National Park, environmental laws relating to sea turtles, and the historical development of Tortuguero. They were also taken on a canal tour to learn about the flora and fauna of the park. In addition to the practical and theoretical training the RAs checked the position and condition of the beach markers in the northern five miles of beach (from the river mouth to the mile five marker); any missing markers were replaced and all markers were repainted white, with the mile numbers in black. 2.2 Track Surveys Weekly track surveys Track surveys were carried out approximately weekly during the entire Green Turtle Program. The track surveyor conducted surveys between the Tortuguero river mouth (mile -3/8) and Jalova lagoon (mile 18). The surveys commenced at dawn (4:30-5:00am) at the Tortuguero river mouth, or at Tortuguero village, and finished between 9:30am-12:00pm at Jalova lagoon. If the survey started at the village, and the section between Tortuguero river mouth and the village had not been surveyed in the morning, the same person surveyed that beach section upon completing the other part of the survey. Only tracks from the previous night were recorded and for each track the following information was recorded: Species Mile Nest or false crawl If the nest and/or turtle was poached If the turtle was depredated by jaguars 7

11 A nest was recorded as poached if there were signs of human disturbance, including footprints around the nest, poke holes from a stick, evidence of digging, an empty egg chamber or fresh egg shells close to the nest. A turtle was considered poached when there was no down track heading back to the sea and there was evidence that she had been flipped over and dragged off the beach (either through the vegetation or to a boat). Dead turtles were considered depredated by jaguars (Panthera onca) when they were surrounded by jaguar tracks or showed characteristic jaguar injuries, such as extensive bites marks to the neck Daily track surveys In addition to the weekly track surveys of the entire 18 miles of nesting beach the FCs and RAs conducted daily track surveys along the northern 5 2/8 miles of beach (from the Tortuguero river mouth to the mile 5 marker) from June - October. These surveys commenced at 6.00am each morning. Only tracks from the previous night were counted, and for each track the following information was recorded: Species Mile Nest or false crawl If the nest and/or turtle was poached If the turtle was depredated by jaguars If the nest was predated by dogs Once a nest had been recorded two lines were drawn through the track to ensure that it was not counted on future surveys. 2.3 Tagging of Nesting Sea Turtles Tagging teams patrolled the beach every night from June - October. The northern part of the beach was divided into two sections: Boca - from the river mouth to the field station (at mile 2 5/8) and Park - from the field station to the mile 5 marker. Separate teams patrolled each section during two shifts: 8pm - 12am and 12-4am, when the number of researchers and volunteer participants allowed. Female turtles encountered during the patrol were tagged after finishing oviposition or when returning to the sea. Leatherbacks (Dermochelys coriacea) were tagged in the rear flippers; green and hawksbill (Eretmochelys imbricata) turtles were tagged axillary, close to the first scale on the front flippers. All turtles were double-tagged to allow identification even if one tag was lost between nesting emergences. For each encounter the following information was recorded: Date Mile marker (to the north of the turtle) Species Tag numbers of existing tags and/or evidence of old tag holes or notches The location of the nest was classified into one of three groups: Open open beach with no vegetation and no shading Border nest partially shaded by vines or other sparse vegetation for some part of the day Vegetation dense vegetation completely shading the nest throughout the day. 8

12 2.3.1 Green turtles Inconel #681 tags were used to tag a minimum sample of 1,000 green turtles not carrying old tags. Every effort was made not to mix Inconel and Monel tags on the same individual. Thus, if a turtle was encountered carrying one Monel tag this was removed and two Inconel tags were applied. If it was not possible to remove the Monel tag for some reason, a second Monel tag was applied to the other flipper. The probability of tag loss was calculated for green turtles tagged with two Inconel #681 tags that were subsequently encountered during the season with one or two tags. The probability of tag loss is: 1 -Ki = 1-((2rdi)/(rsi + 2rdi)) where Ki is the probability of retaining a tag during the interval i; rdi is the number of turtles encountered carrying two tags at interval i; and rsi is the number of turtles encountered carrying one tag at interval i (Wetherall, 1982). Probability of tag loss was estimated for the first-to-last encounter during the 2008 season Hawksbill turtles Hawksbill turtles were tagged with Inconel #681 tags. Once tagged, a disposable sterile scalpel or a biopsy punch was used to collect tissue samples from all hawksbills encountered, when possible. The samples were stored in ethanol until the relevant CITES permits were obtained and then the samples were sent for genetic analysis to Dr Peter Dutton of the National Marine Fisheries Service. Due to the very low level of hawksbill nesting at Tortuguero, and the fact that they are listed as critically endangered, researchers always remained with the turtle until she returned to the sea and then they thoroughly erased the track afterwards, to minimize the possibility of the nest being taken by poachers Leatherback turtles Leatherback turtles were tagged in the rear flippers using Monel #49 tags. 2.4 Biometric Data Collection Green turtles Biometric data were collected from a sample of nesting green turtles. An attempt was made to count one clutch of eggs per night in each of the two beach sections (Boca and Park). Eggs counts were conducted as the eggs were laid, by a person wearing a plastic glove so as not to contaminate the nest. Eggs were counted using an egg counter; any yolkless eggs were counted separately. All egg counts were conducted after midnight, when there were no tour groups present on the beach. All tagged turtles were measured after they had finished nesting, if time allowed. Curved carapace length minimum (CCLmin), from where the skin meets the carapace by the nuchal notch to the posterior notch between the supracaudals, along the midline, was determined to the closest millimeter using a fiberglass tape measure. Straight carapace length maximum (SCLmax), from the anteriormost edge of the carapace to the posterior tip of the longest supracaudal, was determined, to the closest millimeter, using a set of calipers. Both CCLmin and SCLmax measurements were taken three times by the same person, whose name was recorded in the field book, in order to determine the precision of the measurements. Precision is defined as the difference in centimeters between the longest and the shortest of the three measurements. Precision for females encountered more than once during the 2008 season is defined as the difference between the shortest and the longest of all measurements taken from the same turtle over the course of the season. 9

13 2.4.2 Hawksbill turtles CCLmin and SCLmax measurements were taken for all hawksbills encountered during night patrols. As for green turtles, the same observer measured the turtle three times for each measurement, to allow the precision to be calculated. Whenever possible the clutch was counted, if the hawksbill had not already started to lay eggs when encountered Leatherback turtles For leatherbacks, CCLmin (from where the skin meets the carapace by the notch of the neck to the posterior end of the caudal projection, next to the central ridge) was measured using a 300 cm fiberglass measuring tape. Each turtle was measured three times to determine an average CCLmin. No SCLmax measurements were taken as the calipers were not sufficiently large enough to measure a leatherback turtle. 2.5 Fibropapilloma Assessment For a minimum sample of 100 green turtles, those for which clutches were counted, an examination for fibropapilloma was also conducted. All soft body parts, including the cloacal region, were inspected for tumors, using a flashlight with a red filter. The following data were recorded for each assessment: The absence or presence of fibropapilloma tumors Location of fibropapilloma tumors Size of any tumors detected The name of the person examining the turtle Any evidence of fibropapilloma tumors on turtles for which the clutch was not counted was also recorded during the season. 2.6 Determination of Nest Survivorship and Hatching Success A sample of green turtle and hawksbill nests was marked during oviposition. These nests were all located between Tortuguero river mouth (mile -3/8) and the mile 5 marker. The nests were marked using three pieces of flagging tape that were attached to vegetation behind the nest. While the turtle was laying eggs the distance from the centre of the egg chamber to each of these tapes was measured to the nearest cm, so that the location of the nest could be determined at the time of excavation using triangulation. Three marker tapes were used to compensate for the loss of any tapes as a result of camouflaging turtles, insects or persons removing the tapes intentionally; if one marker tape was lost it was still possible to locate the nest using the other two tapes. The distance to the most recent high tide line was also recorded at the time of oviposition. In previous years nests have been excluded from the analysis of survivorship and hatching success because it was not possible to confirm that the excavated nest was in fact the original marked nest (high nesting density can result in other females laying eggs on top or very close to a marked nest). To assist in the positive identification of the marked nest during excavation a small piece of flagging tape with the nest code written on it was deposited in the egg chamber during oviposition. All of the marked nests were inspected daily at 6:00am. Evidence of depredation, poaching or beach erosion were noted and resulted in termination of monitoring for that nest; if the evidence was inconclusive, monitoring continued as normal, but the date of the observed disturbance was recorded, so that any resulting anomalous excavation data could be accounted for. If evidence of hatching was observed, the date was noted and the nest was excavated two days later. If no depression or hatchling 10

14 tracks were recorded, the nest was excavated after 65 days (75 days for any leatherback nests marked). After 65 days, or sooner if signs of emergence had been recorded, the nest was excavated, once the distances from the marker tapes had been re-measured to confirm that it was the original nest. Nests that had no obvious depressions were located by probing for soft sand using a wooden stick (only after 65 days, when it was presumed that hatching and emergence had occurred), and this technique greatly aided in locating several of the marked nests. The excavation was discontinued if the researcher encountered a large number of hatchlings in the nest; in such cases the hatchlings were re-buried and the nest excavated at a later date. If a few hatchlings were encountered, they were placed in a shallow hole close to the nest site and covered with sand so that they could reach the sand surface and emerge the following night. For each nest the following information was recorded during the excavation: Nest code Mile marker Name of persons conducting excavation Date laid, hatched (if available) and excavated Number of empty shells only shells corresponding to more than 50% of the egg were counted Number of hatchlings alive or dead Number of unhatched eggs - these were categorized as o Without embryo no visible embryo observed o Embryo an embryo at any stage of development was present o Full embryo a fully developed embryo was present Number of pipped eggs embryo had broken the shell but failed to hatch Number of predated eggs Number of deformed embryos including albinism or multiple embryos in a single egg Number of yolkless eggs If the nest identification tape was found Any other pertinent information In addition, the depth from the surface to the top of the egg chamber (to the first egg encountered), and the bottom of the egg chamber (after the last egg was removed) was measured to the nearest centimeter. If a nest could not be found when excavated, an attempt was made to determine the fate of the nest. Nests were considered poached if an empty egg chamber was encountered. Nests were assumed dugup by another turtle if broken eggshells and a new body pit were encountered where the original nest was supposed to be located. Nests were considered depredated if a large number of opened eggshells were found in close proximity to the location of the marked nest, and there were signs of digging by animals, or tracks. An attempt was made to identify the predator if possible. If human footprints and digging was observed at the location of the nest, the nest was considered dug-up by tour guides or other persons to show the hatchlings to tourists. Nests for which the fate could not be determined with certainty or which were not excavated entirely were excluded from the subsequent analysis of nest survivorship and hatching success. 2.7 Physical Data Collection Throughout the 2008 Green Turtle Program several environmental variables were monitored on a daily basis at the John H. Phipps Biological station in Tortuguero. 11

15 Rainfall was collected in a gauge that was emptied each day at 9.00am and recorded to the closest 0.1mm. Air temperature was recorded at 9.00am; the minimum and maximum values for the previous 24 hours, and the current temperature were noted. Sand temperature was measured using data loggers buried at 30, 50 and 70cm depth in the open, border and vegetation zones of the beach in front of the CCC station. The data loggers were set to take a temperature reading every hour. The data were downloaded in the middle and at the end of the 2008 Green Turtle Program. 2.8 Collection of Human Impact Data Visitors to Tortuguero The number of visitors paying to enter the CCC Natural History and Visitors Center was recorded each day during 2008 by the Visitor Center Administrator. Staff at the Tortuguero National Park headquarters at Cuatro Esquinas provided information on tourist visitation to the park during Capacity of hotels and cabinas To monitor the growth of tourism development in Tortuguero a survey was conducted on the capacity of the hotels and cabinas in the region. The FCs, Xavier Debade and Dagnia Nolasco collected information on the room and bed capacity from cabina owners and hotel managers in Tortuguero at the end of the 2008 Green Turtle Program Turtle tours The number of tourists going on guided turtle tours during the 2008 Green Turtle Program was calculated from the permits issued to tour guides by Tortuguero Conservation Area (ACTo). In 2008, the Turtle Spotter Program, the visitation system introduced in 2004 that aimed to reduce negative impacts of tourism on nesting sea turtles, was implemented for the entire northern five miles of beach where tourism is permitted (from the Tortuguero river mouth to the mile 5 marker). A new funding mechanism was implemented in 2007; an information brochure about the Turtle Spotter Program was designed and offered to tourists participating in turtle tours for a donation of $4. Each brochure contained a sticker which visitors were encouraged to wear during their tour, to show their support for the Program. Funds generated from these brochures were used to employ fourteen turtle spotters from the community of Tortuguero; in 2008 a coordinator was also contracted to oversee the daily organization of the Program activities and the sale of the brochures. The turtle spotters patrolled the beach searching for nesting turtles, and reported their location to the tour groups waiting with their guides at designated areas behind the beach. When the turtle was close to laying eggs, guides led their group to her location using a path behind the beach, thus reducing the number of people walking along the beach who could potentially disturb other turtles as they came ashore to nest Artificial lights To assess the level of impact of artificial lights on the Tortuguero nesting beach a light survey was conducted each month. Dates as close as possible to the new moon were selected when natural light levels on the beach were minimal. The beach was surveyed from the Tortuguero river mouth to the mile 5 marker, commencing at 8.00pm. For each survey the following data were recorded: Date Beach section Boca or Park Name of observers 12

16 Mile section Number of lights visible from the beach Light source (if possible to determine) Location of light source (beach side or river side) To avoid duplicate recording of the same light source in more than one 1/8 mile section of beach, only those lights that could be seen while viewed perpendicular from the beach were recorded in each 1/8 mile Hatchling orientation and disorientation Hatchling orientation was determined for a sample of nests from which hatchling tracks were observed. For each nest the following information was recorded: Date Nest code (if it was a marked nests) Name of observers Mile section Distance from the nest to the most recent high tide line (m) Approximate number of tracks Number of outliers Number of circlers hatchlings that didn t go directly to the sea, that were maybe disorientated In addition, at a distance of 10m from the nest, using a compass held at waist height above the nest, the following data were recorded: Angular range of all tracks (in ) Angular range of tracks minus any outliers (in ) Modal direction of tracks Any evidence of hatchling disorientation was also recorded, for marked or unmarked nests. Where possible the light source causing the disorientation was noted in addition to the number of disorientated hatchlings and the number that reached the sea. 2.9 Environmental Education and Outreach Activities Presentations about sea turtle biology, conservation and the work of the CCC in Tortuguero were given opportunistically to groups staying at or visiting the John H. Phipps Biological Station. In addition, the 2008 Green Turtle Program RAs, supervised by FC Dagnia Nolasco, implemented a series of environmental education activities at the Tortuguero school and high school, and also at the school in San Francisco village. In response to concerns in 2007 from CCC, local guides and National Park staff about the level of dog predation of turtle nests and the increasing population of dogs in the village, a committee was organized comprising representatives from interested groups and individuals to coordinate a veterinarian spay/neuter clinic and educational program in 2008 with the aim of reducing the dog population and also providing advice to local residents on how to care for their pets. The first of these clinics was held during the 2008 Leatherback Program and CCC remained an active member of the organizing committee throughout 2008, helping to plan two further clinics. 13

17 2.10 Independent Research Projects Two independent research projects were conducted during the 2008 Green Turtle Program which focused on the impacts of tourism on the green turtle population in Tortuguero; the projects were designed to gather information that could be used to help effectively manage the Turtle Spotter Program so that if fulfilled its objective of minimizing the negative impacts of tourism on sea turtles in the area Impact of tourist presence on the nesting behavior of green turtles An undergraduate student from Colombia (Catalina González Príeto) studied the behavior of female green turtles subject to various levels of tourist impact during nesting. For 50 females, three different phases of the nesting process (oviposition, covering and camouflaging) were timed to the nearest second using a handheld stopwatch; the total number of people present around the turtle was also recorded. Only these phases of the nesting process were selected as tourists are not permitted to approach the turtle until she has started to lay her eggs. Subsequent analyses compared the behavior of females with respect to the number of people who had been present during the nesting process Effect of nest trampling on the hatching and emerging success of green turtle nests A potential negative impact of large numbers of tourists walking on Tortuguero beach is a reduced hatching or emerging success resulting from the physical trampling of nests during the incubation period. An undergraduate student from Spain (Luis Gonzalez) investigated the effect of different levels of nest trampling on the subsequent hatching and emerging success of the nests. To control the level of trampling the study was conducted beyond the mile five marker; in an area of the beach where tourism in not permitted. Pairs of nests were marked on the same night, within the same beach zone (border or open) and within 500m of each other. One of the pair was a control nest (no trampling) and the other was an experimental nest (trampling). The nests were marked using the same method described in section 2.6 and were monitored on a daily basis throughout the incubation period. Twice a week the experimental nests were subject to trampling; one person would walk over the nest a designated number of times, to simulate a specified number of tourists. Experimental nests were classified as either Low Impact the equivalent of 40 people a week, or High Impact the equivalent of 200 people a week. Trampling was discontinued after day 50 and nests were excavated after 65 days; the protocol for nest excavations was the same as that detailed in section 2.6. Pairs of nests were compared to determine if there was any difference in either hatching or emerging success that could be related to the effect of trampling. 3. Results 3.1 Preparations The RAs arrived in Tortuguero on 9 June, During the first two weeks of the 2008 Green Turtle Program the RAs received an intensive training program and general orientation. This included lectures about sea turtle biology, conservation, tourism in Tortuguero, and the history and structure of CCC. There was also a detailed explanation of the Green Turtle Program monitoring protocol. In addition to theoretical instruction they also received practical training in flipper tagging, nest marking and other data collection procedures from the FCs. Training patrols were conducted on several nights along sections of beach close to the field station (between the Tortuguero river mouth and mile 5), during which the FCs demonstrated field techniques and supervised RAs tagging and measuring turtles, and recording data in the field books. To have a better understanding of the National Park, 14

18 environmental laws and the community, the RAs spoke to park rangers and members of one of the founding families of Tortuguero to learn about the history and development in the area. To facilitate the environmental education program there were also visits to the school and high school in Tortuguero, and the school in San Francisco. RAs also visited the biological research station at Caño Palma to talk to investigators conducting sea turtle research north of the Tortuguero river mouth. During the first week of the program the mile markers on the beach between the Tortuguero river mouth (mile -3/8) and the mile 5 marker were replaced and/or repainted as necessary, to ensure that there were three markers at each 1/8 of a mile. These markers were put in the same locations as those positioned at the start of the 2008 Leatherback Program. 3.2 Track Surveys Weekly track surveys A new track surveyor, Jorge Ivan Ramos, was contracted in August, He received training from the FCs and Scientific Director in how to conduct the track surveys and the data collection forms. Forty-nine weekly track surveys were conducted from 6 January to 27 December Nesting of green turtles was observed regularly from March - November (See Figure 1), although the first nest was recorded on 3 February. Peak nesting was observed on 30 August when 2,243 nests were recorded in a single night, although there was also a distinct peak earlier in the season, around mid- July (See Figure 1). Using the methodology of Troëng & Rankin (2005), it was estimated that 107,852 green turtle nests were laid along the entire 18 miles of beach during the 2008 nesting season (See Figure 2). This equates to a population of between 17,975 38,519 nesting females. As observed in previous years, green turtle nesting density was found to be highest away from the river mouths that mark the end of the beach; the least stable sections of nesting habitat. Although there was no clear peak, increased nesting was observed within Tortuguero National Park, between miles 4-14, with the highest density occurring just south of the centre of the beach at mile 12 (See Figure 3). Nests laid between the Tortuguero river mouth and the mile 5 marker, where nightly beach patrols were regularly conducted, accounted for 17.4% of all nests laid on the entire beach (See Figure 3). Between 3 February (the first date that green turtle nesting activity was observed) and 1 November the track surveyor reported a total of 23 green turtles that had been killed by jaguars the night before the survey; on 6 and 20 September five females were killed in a single night. In addition, one hawksbill turtle was found killed by a jaguar on 7 June. Very low levels of hawksbill nesting activity were recorded during the weekly track surveys in 2008; six hawksbill nests were observed between 10 May 21 June; on 7 June three hawksbill nests were recorded from one night. Leatherback nesting activity was observed from late February to early June, with peak nesting occurring on 17 May when six nests were recorded. It was estimated that a total of 256 leatherback nests were laid in 2008 (See Figure 4). For a more detailed discussion of the temporal and spatial distribution of leatherback nesting in 2007, and levels of illegal take, see Debade et al (2009). 15

19 Figure 1. Temporal distribution of green turtle nesting at Tortuguero in 2008, as determined from weekly track surveys Number of nests/false crawls Jan 16-Jan 31-Jan 15-Feb 1-Mar 16-Mar 31-Mar 15-Apr 30-Apr 15-May 30-May 14-Jun 29-Jun 14-Jul 29-Jul 13-Aug 28-Aug 12-Sep 27-Sep 12-Oct 27-Oct 11-Nov 26-Nov 11-Dec 26-Dec Date Nests False Crawls 16

20 Figure 2. Green turtle nesting trend at Tortuguero, , as determined by weekly track surveys of the entire beach 200, , , ,000 Number of nests 120, ,000 80,000 60,000 40,000 20, Year 17

21 Figure 3. Spatial distribution of green turtle nesting at Tortuguero in 2008, as determined from weekly track surveys % of green turtle nests / Mile 18

22 Figure 4. Leatherback nesting trend at Tortuguero, , as determined by weekly track surveys 2,000 1,800 1,600 1,400 Number of nests 1,200 1, Year 19

23 3.2.2 Daily track surveys Daily track surveys were conducted by the FCs and RAs between 14 June and 1 November (except for 15 and 18 June). A total of 18,037 green turtle nests and 17,348 green turtle false crawls were recorded between the Tortuguero river mouth and the mile 5 marker (See Figure 5); successful nesting was observed in 51.0% of female emergences. In addition, nine leatherback nests, 21 hawksbill nests, 3 leatherback false crawls and 17 hawksbill false crawls were also observed. Figure 5a shows the spatial distribution of nests and false crawls for the northern 5 2/8 miles of beach. Nesting density per 1/8 mile was greater within the National Park (past 3 3/8), except for miles 0, 1/8 and 2/8. Subsequently the overall number of nests recorded was much greater within the limits of the park (55.0% compared to 45.0% outside the park). As in previous years, nesting density was lowest close to the river mouth (between mile -3/8 and -1/8) and in front of Tortuguero village (miles 2 7/8-3 2/8). The temporal distribution of nesting for the 2008 Green Turtle Program is shown in Figure 5b. Peak nesting activity was recorded on 9 September, when 448 green turtle nests were counted from the previous night; more than 400 nests were also recorded on 11 and 29 September. Nesting activity remained above 50 nests per night from 8 July - 14 October (except for 11, 12 and 21 July). Even towards the end of October more than 15 nests were observed each night. Nine leatherback nests and three false crawls were counted during the same time period; the last nest was recorded on 13 July. Hawksbill nesting activity was observed from June to October with a total of 21 nests and 17 false crawls recorded during track surveys. The majority of nests were observed from June to August (three hawksbill nests were counted on 8 July) with a few nests recorded right at the end of October; the last on 23 October. During the daily track surveys researchers also noted the level of illegal take of both eggs and female turtles (See Figure 6). In total, 276 green turtle nests (1.5% of the total number laid) and 34 females were taken from June - October. In addition, one leatherback and one hawksbill nest were also poached. From Figure 6a it can be seen that the majority of nest poaching occurred towards the Tortuguero river mouth, between mile -3/8 and mile 0; there was also an increase close to the airport (mile 4/8-5/8). It is disturbing to note a sharp increase in the number of nests taken illegally just inside the limit of Tortuguero National Park (miles 3 3/8-3 5/8). Poaching of turtles was more evenly distributed throughout the five miles, though more females were taken close to the river mouth (See Figure 6a). From 14 June - 31 October, poaching (of either nests or turtles) was observed during 101 of 140 (72.1%) track surveys (See Figure 6b). The highest number of poached nests was recorded on 20 July, when 19 green turtle nests were taken in one night. Poaching was observed throughout the nesting season although there seemed to be more consistent illegal take in September and October (See Figure 6b); poaching of turtles was also more prevalent in those months. In addition, 60 green turtle nests were recorded as depredated by dogs from June - October. Groups of dogs were often observed by researchers during track surveys, occasionally with more than 10 individuals. Most dog predation was observed close to the village (between miles 2 5/8-3 2/8) though dogs were also occasionally seen north of the CCC station. It was also worrying to observe that 19 nests (31.7% of all those depredated) were located within Tortuguero National Park. It is hoped that the veterinary spay/neuter clinics will reduce the negative impact that the dogs are having. 20

24 Figure 5. Results of daily track surveys of the northern 5 2/8 miles of beach in 2008 a) Spatial distribution Number of green turtle nests/false crawls /8-1/8 1/8 3/8 5/8 7/8 1 1/8 1 3/8 1 5/8 1 7/8 Nests 2 1/8 Mile False Crawls 2 3/8 2 5/8 2 7/8 3 1/8 3 3/8 3 5/8 3 7/8 4 1/8 4 3/8 4 5/8 4 7/8 b) Temporal distribution Number of green turtle nests/false crawls Jun 21-Jun 28-Jun 5-Jul 12-Jul 19-Jul 26-Jul 2-Aug 9-Aug 16-Aug 23-Aug 30-Aug 6-Sep 13-Sep 20-Sep 27-Sep 4-Oct 11-Oct 18-Oct 25-Oct 1-Nov Date Nests False Crawls 21

25 Figure 6. Illegal take of green turtle nests and females in 2008, as determined from daily track surveys of the northern 5 2/8 miles of beach a) Spatial distribution Number of nests/turtles /8-1/8 1/8 3/8 5/8 7/8 1 1/8 1 3/8 1 5/8 1 7/8 2 1/8 2 3/8 2 5/8 2 7/8 3 1/8 3 3/8 3 5/8 3 7/8 4 1/8 4 3/8 4 5/8 4 7/8 Mile Nests Turtles b) Temporal distribution Number of nests/turtles Jun 20-Jun 27-Jun 4-Jul 11-Jul 18-Jul 25-Jul 1-Aug 8-Aug 15-Aug 22-Aug 29-Aug 5-Sep 12-Sep 19-Sep 26-Sep 3-Oct 10-Oct 17-Oct 24-Oct 31-Oct Date Nests Turtles 22

26 3.3 Tagging of Nesting Sea Turtles Tags used during the 2008 Green Turtle Program were National Band & Tag Company (NBTC) Monel #49 tags VC1032, VC1033, VC1036, VC1103 and VC1104, and Inconel #681 tags , , , , , and Green turtles A total of 2,373 green turtle encounters were recorded during 2,065 team hours of night patrols between 12 June and 30 October 2006 (See Appendix 1). These encounters included 1,891 individual females; 1,367 (72.3%) initially observed without tags and 524 (27.7%) who had tags. In addition there were 482 encounters with turtles observed more than once during the 2008 nesting season. During the 2008 Green Turtle Program, 22 green turtles tagged at other nesting beach projects in Costa Rica were encountered; 10 were tagged by researchers from the Caño Palma turtle monitoring project (which is based north of the Tortuguero river mouth), seven were tagged in Mondonguillo, three in Parismina and two in the Pacuare Nature Reserve, which are beaches south of Tortuguero National Park. In addition there were two females observed with tags from Panama; one was thought to have been tagged at Soropta Beach in 2005, and the other was originally tagged in 2006 at the CCC monitoring project at Chiriquí Beach. Both of these beaches are in the Bocas del Toro province of Panama. Another turtle was also encountered bearing tags that had a return address on the reverse of the tag from Cuba. The Scientific Director was in touch with researchers from Cuba who were able to provide the original tagging data; this turtle was tagged on feeding grounds off Nuevitas in June At that time she had a curved carapace length of 99cm and a straight carapace length of 95cm, and was classified as an adult female. At the same time the Cuban researchers were also able to provide the tagging data for the green turtle killed by a jaguar in 2007 that also had Cuban tags; that female was tagged in Nuevitas in June She had a curved carapace length of 78cm and a straight carapace length of 75cm; due to her size she was classified as either male or female. The remaining 499 females that had tags were all originally tagged in Tortuguero. Ninety-six individuals had been tagged more than 10 years previously and there were seven who were tagged more than 20 years ago. Two females were observed in September (Id# and 21487), who were both first tagged in 1980; this sets a new longest nesting history record for a green turtle at the Tortuguero project. Female was observed in three nesting seasons; 1980, 1986 and 1999, but she has not been encountered since then. The other female (#21487) has been seen 36 times in 10 different seasons; she was originally tagged at mile 2 and when she was observed in 2008 she was in mile 2 2/8. It is also interesting that in 1988 this female was recorded as having a large tumour in one of her flippers, but this was not noted in 2008 during the general revision of the turtle after tagging. Of 1,367 newly tagged green turtles, 194 (14.2%) were recorded as having evidence of either old tag holes or notches in at least one front flipper when encountered for the first time during the 2008 Green Turtle Program. Tagging efficiency for green turtles emerging (nests and false crawls) between the Tortuguero river mouth and the mile 5 marker on nights before track surveys (n = 136) ranged from 0% to 44%, with an overall mean of 6.7%. Beach zone was recorded for 2,364 green turtles encounters; 18.8% (n = 445) of those females nested in the open zone, 72.3% (n = 1,710) were located in the border zone, 5.8% (n = 137) in the vegetation 23

27 zone and 3.0% of turtles were encountered while making a false crawl (n = 72). Of 219 turtles tagged with two tags and seen again during the 2008 Green Turtle Program, 28 were reported to have lost one tag, resulting in an overall within-season probability of tag loss of 6.8%. Table 1a highlights the differences observed in tag loss between turtles tagged in different months; the highest tag loss was seen for turtles tagged in July (10.8%) and the lowest was observed for turtles tagged in October (2.9%). Tag loss was seen to decrease later in the season; August = 3.3% and September = 2.9%. There was also considerable variation in the probability of tag loss between researchers, ranging from 0% to 60% (See Table 1b); the high overall tag loss can probably be attributed to just a few people who had difficulties tagging. Table 1. Probability of within-season tag loss from first-to-last encounter a) By month Month r di r si 1-K i ± 95% CL June ± July ± August ± September ± October ± Total ± b) By tagger Tagger r di r si 1-K i ± 95% CL RA ± 0 RA ± 0 RA ± 0 RA ± 0 RA ± 0 FC ± 0 RA ± 0 RA ± 0 RA ± 0 RA ± 0 RA ± 0 RA ± 0 RA ± 0 RA ± 0 RA ± RA ± RA ± FC ±

28 Key to table Table 1. Continued Tagger r di r si 1-K i ± 95% CL RA ± RA ± RA ± RA ± RA ± RA ± RA ± Total ± FC = Field Coordinator RA = Research Assistant Mixed taggers = Two RAs tagged the same turtle r di = Number of green turtles encountered with two tags r si = Number of green turtles encountered with one tag 1-Ki = Probability of tag loss 95% CL = 95% confidence limits New green turtles were tagged throughout the entire season, including October (n = 255); in previous years no new turtles have been tagged in the last month of night patrols, but a survey in 2007 suggested that there were still a large number of untagged females arriving late in the nesting season. In 2008 additional tags were purchased to ensure that tagging could be conducted until the end of the Green Turtle Program Hawksbill turtles Eleven female hawksbill turtles were encountered during the 2008 Green Turtle Program (See Appendix 1). Of these, eight were newly tagged, and three were previously tagged; one in Tortuguero in 1998, one in Tortuguero in 2001 and the other by researchers at Caño Palma in Of these 11 individuals two were seen twice during the nesting season. None of the newly tagged hawksbill turtles (n = 8) showed evidence of previous tags. All hawksbills encountered nested successfully; two (15.4%) nests were laid in the open zone, nine (69.2%) were laid in the border zone and two were laid in the vegetation zone (15.4%) Leatherback turtles A total of five leatherback encounters were recorded at the beginning of the 2008 Green Turtle Program; the last encounter was on 12 July. Four individual females were observed; one of the turtles had no tags, one had tags from Tortuguero in 1996 and the other two were renesters who had been observed during the 2008 Leatherback Program (one was newly tagged and the other was a remigrant). All five encounters occurred during successful nesting attempts; all nests were laid in the open zone. 3.4 Biometric Data Collection Green turtles Table 2 shows the mean carapace length and clutch size of green turtle females measured during the 25

29 2008 Green Turtle Program. To ensure independence of the data, only the first measurements taken for each individual were included in the analysis. The overall mean curved carapace length (CCLmin) was 105.3cm (Range = cm) and the overall mean straight carapace length (SCLmax) was 99.0cm (Range = cm). There was no real difference in carapace length between newly tagged females (with or without evidence of previous tags) and previously tagged females (See Table 2). Clutch size ranged from eggs for all nests counted ( x = 111 eggs, n = 114; See Table 2). Newly tagged females (with or without evidence of tags) laid slightly smaller clutches than previously tagged individuals (See Table 2). Table 2. Mean carapace length and clutch size of green turtles Sample Newly tagged females no OTH/OTN Newly tagged females OTH/OTN CCLmin / cm SCLmax / cm Clutch size / eggs n x ± S.D. n x ± S.D. n x ± S.D ± ± ± ± ± ± 24 Previously tagged females ± ± ± 20 All ± ± ± 21 OTH = Old tag hole, OTN = Old tag notch For green turtles both CCLmin and SCLmax were measured with a slightly greater degree of precision by research assistants than by participants (See Table 3a), although the range of precision values were similar for both groups. The two different carapace measurements taken during one encounter were equally precise (See Table 3a). For females encountered and measured on two or more occasions during the 2008 Green Turtle Program, the SCLmax measurements were taken with a higher level of precision than the CCLmin measurements (Table 3b) when the female was seen two or three times; if she was seen more than three times then there was the same degree of precision for the two different measurements. For both CCLmin and SCLmax measurements there were several occasions when the difference between the length measurements on subsequent encounters was greater than 2cm (See Range values in Table 3b). Table 3. Precision of carapace measurements for green turtle females a) During the same encounter Observer CCLmin / cm SCLmax / cm n x ± S.D. Range n x ± S.D. Range Research assistants ± ± Participants ± ± Total ± ±

30 b) Between encounters CCLmin / cm SCLmax / cm Encounters n x ± S.D. Range n x ± S.D. Range ± ± ± ± ± ± ± ± Hawksbill turtles Carapace measurements were taken for all of the eleven hawksbill females observed during the 2008 Green Turtle Program (See Table 4). CCLmin ranged from cm and SCLmax from cm. Newly tagged females, on average, had the same mean curved carapace length, but a smaller mean straight carapace length than the previously tagged individuals encountered (See Table 4). Average size for the two clutches that were counted was 152 eggs. Table 4. Mean carapace length of hawksbill females Sample CCLmin / cm SCLmax / cm Clutch size / eggs n x ± S.D. n x ± S.D. n x ± S.D. Newly tagged females ± ± ± 1.4 Previously tagged females ± ± N/A All ± ± ± 1.4 For newly tagged hawksbill turtles, the precision of CCLmin measurements was the same as that of SCLmax measurements, x = 0.2cm (See Table 5). Previously tagged females had a slightly greater precision for SCLmax measurements than CCLmin (See Table 5). An inter-species comparison shows that the precision of both CCLmin and SCLmax measurements is slightly greater for hawksbills than for greens or leatherback turtles (See Table 3a and Table 5). Table 5. Precision of carapace measurements for hawksbill females Sample CCLmin / cm SCLmax / cm n x Range n x Range Newly tagged females Previously tagged females All Leatherback turtles During the 2008 Green Turtle Program biometric data were collected for four leatherback females (See Table 6). The overall mean carapace length (CCLmin) of leatherbacks was 152.2cm, with a range of 27

31 cm (See Table 6). Three leatherback clutches were counted; with an overall mean of 61 eggs and 41 yolkless eggs. The precision of leatherback CCLmin measurements was 0.6cm, with a range of cm. Sample Table 6. Mean carapace length of leatherbacks n CCLmin / cm x ± S.D. n Clutch size / eggs Normal eggs x ± S.D. Yolkless eggs x ± S.D. Newly tagged females ± ± ± 9.9 Previously tagged females ± All ± ± ± Fibropapilloma Assessment A total of 192 green turtles were subject to a thorough examination for the presence of fibropapilloma tumors; three individuals (1.6%) were recorded to be affected. One had a tumor on her cloaca; one had two tumors on her flippers and one had four tumors on her flippers and head ranging in size from 1 7cm. Two were newly tagged females, the other was a remigrant tagged female. In addition to the females who were checked specifically for the presence/absence of fibropapilloma, tumors were also recorded for another seven individuals; these were observed during the routine check for physical abnormalities conducted for each turtle encountered. One female was encountered on two separate occasions, and tumors were recorded both times. Of these seven individuals, two were remigrants with tags and five were newly tagged individuals. Tumors ranged in size from 1 5cm, and in the majority of cases were located on the front flippers or the neck/shoulder area. 3.6 Determination of Nest Survivorship and Hatching Success The mammal predators observed disturbing nests or taking hatchlings during the 2008 Green Turtle Program were domestic dogs (Canis familiaris) and humans (Homo sapiens sapiens). No other predators were observed disturbing eggs or taking hatchlings; however, during the excavation of marked nests following the emergence of hatchlings evidence of predation by fly larvae (Megaselia scalaris) was documented Green turtles A total of 145 green turtle nests were marked between 11 May and 1 October, 2008; three of which were marked during the 2008 Leatherback Program. Of these nests, on six occasions the nest was not found during the excavation and the fate could not be determined with certainty; another three nests could not be excavated as another turtle had laid a nest very close to the marked nest, so the excavation could not be conducted without disturbing the new nest; for one nest all three flagging tapes were lost and for another there were still live embryos in the eggs at the end of the Green Turtle Program on 30 November, These 11 nests were excluded from subsequent analysis, leaving a sample of 134 green turtle nests monitored from the date of oviposition until their fates could be determined. Table 7 lists the fate of all of the green turtle nests marked in It can be seen that the majority of nests (73.1%) remained undisturbed during incubation (n = 98). Of those that were disturbed, poaching accounted for 13.4% (plus an addition 2.2% of nests that were partially poached) and nesting 28

32 turtles partially destroyed 5.9% of marked nests. Very few nests were depredated, inundated or completely destroyed by another nesting turtle, and only four nests were partly or completely unhatched. Fate Table 7. Fate, hatching and emerging success of marked green turtle nests in 2008 Boca n Park n Total n % of total Hatching success (%) Emerging success (%) 1. Undisturbed Poached Partly destroyed by other turtle Partly poached Partly hatched Unhatched Depredated Inundated Destroyed by other turtle Total Not included in analysis Unknown Two nests together All three tapes lost Live embryos in nest Total Calculated as the mean of all 134 nests Data from the nest excavations of the 134 green turtle nests monitored through incubation are summarized in Table 8. Overall hatching success was calculated as 84.1% (n = 134) and overall emerging success was estimated as 80.7% (n = 134) (See Table 7). These values were determined as the mean of all 134 marked nests for which the fate could be determined. The hatching and emerging success of partly poached, depredated and destroyed nests should be viewed with caution as they are not a true representation of the success of these nests, as very few eggs were found during the excavations and so the hatching success was artificially increased. If these three categories are removed from the determination of the overall hatching and emerging success the values are 85.2% and 82.5%, respectively. Average clutch size (determined from egg counts conducted at the time of oviposition) was eggs (n = 142); this value includes nests that were subsequently excluded from the analysis of hatching and emerging success. Of the 134 nests included in the analysis of hatching and emerging success the majority (63.9%) were laid in the border zone (n = 91), 32 were deposited in the open zone and just 11 (8.2%) were laid in the vegetation. There was no obvious correlation between nesting zone and the level of disturbance, ie. disturbed nests showed the same prevalence for the border zone as undisturbed nests. 29

33 Table 8. Summary of excavation data for green turtle nests marked in 2008 Fate * n Live Hatchlings Dead Empty shells Pipped eggs No embryo Unhatched eggs Embryo Full embryo Depredated eggs Yolkless eggs Total , * For fate code details see Table 7 30

34 A comparison between egg counts at the time of oviposition and at excavation for a sample of undisturbed nests (n = 98) shows a mean of 4.3 less eggs counted at the time of excavation than at the time of oviposition (range: -48 to +39 eggs, SD = 13.7 eggs). The distance between the sand surface and the top eggshell at the time of excavation for undisturbed nests (n = 99) ranged between 25 and 110 cm with a mean of 56.9 cm. The distance between the sand surface and the bottom of the egg chamber varied between 40 and 135 cm with a mean of 72.7 cm. The incubation period for undisturbed nests for which emerging was observed (n = 66) ranged from 51 to 66 days with a mean of 57 days. Unhatched eggs that contained albino, twin, triplet and deformed embryos accounted for 0.25% of all eggs laid in undisturbed and disturbed nests that were excavated (See Table 9). Of the deformed embryos five were found in the same nest; one of which was still alive in the egg Hawksbill turtles Table 9. Incidence of albinism, twins and deformed embryos in 2007 Type of abnormality n % of total Albino Twin Deformed embryo Total Five hawksbill nests were marked between 30 August and 29 September All of these nests were undisturbed during the incubation period, and hatched successfully. The results of the excavations of hawksbill nests are summarized in Table 10. Mean hatching success was 77.9% (range = 68.1% 95.5%) and emerging success was 50.9% (range = 6.1% %); these values were determined as the mean for all five nests excavated. Two of the nests had considerable numbers of live or dead hatchlings encountered during the excavation; if these are excluded from the determination of emerging success the value is 67.6%. It is interesting that all five nests had some depredated eggs present. Two females laid a single yolkless egg each, and one albino embryo was found in an unhatched egg. No deformed embryos or hatchlings were recorded. Table 10. Summary of hawksbill nest excavations from 2008 Fate 1 n Empty shells Hatchlings Live Dead No embryo Unhatched eggs Embryo Full embryo Pipped Depredated Hatching success % Emerging Success % For fate code details see Table 7; 2 92 from one nest; 3 78 from one nest Mean incubation period was 59 days (n = 3), with a range of days. The mean distance between the sand surface and the top eggshell at the time of excavation for hawksbill nests (n = 5) was 42.0 cm (Range = cm). The mean distance between the sand surface and the bottom of the egg chamber was 56.2 cm (Range = cm). 31

35 3.6.3 Leatherback turtles The hatching and emerging success of leatherback nests laid at Tortuguero during 2008 is discussed in detail in Debade et al. (2009). 3.7 Physical Data Collection Rainfall Rainfall was recorded daily from 1 March - 30 November, 2008, during the Leatherback and Green Turtle Programs (See Table 11). The pattern of rainfall in 2008 was similar to that observed in previous years. The driest month was September with a total of 145.3mm of rain recorded. In contrast, the end of the nesting season had the most rain, with 885.6mm recorded during November. June was also a very wet month, with 661.6mm of rain. The total amount of rain recorded at the station during the months with monitoring activities was 3,294.1mm; an average of 12.5mm per 24 hours. Average rainfall each month ranged from 5.2mm to 29.5mm per 24 hours (September and November, respectively). The highest rainfall recorded for a single 24 hour period was on 26 November, with 126.6mm; this was almost as much as the total rainfall during the entire month for March, May or September. Table 11. Summary of rainfall data March to November, 2008 Month Total rainfall mm/month x rainfall mm/24 hours March April May June July August September October November Total 3, Data for 72 hours March 2 Data for 48 hours 20-21, April 3 Data for 48 hours May 4 Data for 48 hours 8-9, July 5 Data for 48 hours 5-6, August 6 Data for 48 hours 18-19, 30 September-1 October 7 Data for 48 hours 5-6 October Air temperature Minimum, current and maximum air temperature was recorded daily from 1 March - 30 November, Mean monthly minimum and maximum air temperatures for months when monitoring activities were conducted during 2008 are shown in Table

36 Table 12. Summary of air temperature data March to November, 2008 Month Mean minimum air temp / C Mean maximum air temp / C March April May June July August September October November Overall mean Data for 48 hours March 2 Data for 48 hours April 3 Data for 48 hours May 4 Data for 48 hours 5-6 June 5 Data for 48 hours 4-5, 8-9 July 6 Data for 48 hours 5-6, 12-13, 31 August- 1 September 7 Data for 48 hours 3-4, 18-19, 30 September-1 October 8 Data for 48 hours 5-6 October 9 Data for 48 hours November Recorded air temperature ranged between 20 C and 31 C during the period of monitoring activity. November was the coolest month, with the lowest mean minimum and maximum temperatures (22.3 C and 25.5 C, respectively); April had the highest mean maximum temperature (29.0 C). The daily variation in temperature ranged from 0-8 C, with an average of 4.7 C difference between the minimum and maximum temperature recorded over a 24 hour period Sand temperature Mean sand temperatures recorded during the 2008 Green Turtle Program are shown in Table 13. Mean monthly sand temperatures ranged from ºC between June and October. It can be seen from the table that there are no data recorded after 15 October; on 30 November the data loggers in the vegetation and border zones were all retrieved successfully but one had stopped working (Vegetation 70cm) and for the others the data could not be downloaded properly. In addition, none of the Open zone data loggers could be found; they were presumed washed out by high tides during November. Table 13. Mean monthly sand temperatures during the 2008 Green Turtle Program Zone Vegetation x temperature / ºC Border x temperature / ºC Open x temperature / ºC Depth / cm June N/A July - to 8/7 N/A Retrieval depth / cm 8 July N/A

37 Table 13 Continued. Mean monthly sand temperatures during the 2008 Green Turtle Program Zone Vegetation x temperature / ºC Border x temperature / ºC Open x temperature / ºC Depth / cm July - from 8/7 N/A August N/A September N/A October - to 15/10 N/A Retrieval depth / cm 15 October N/A October - from 15/10 November Retrieval depth / cm 30 November N/A N/A N/A Overall mean N/A N/A = No data logger at that depth during that month 1 Data logger stopped working on 12 April 2 Data logger recovered but problem downloading data 3 Data logger had stopped working a malfunction indicator light was observed on 30 November 4 Data logger lost between 15 October and 30 November possibly due to erosion from high tides Figure 5 shows the mean monthly sand temperatures for the different beach zones during the 2008 Green Turtle Program. There was an increase in sand temperature in all zones, and at all depths from July to September, and then temperatures showed a slight decline in the first half of October. It would have been very interesting to see what happened late in the season, as there was increased rainfall in the last two months of the program (See Table 11) which would have been expected to cause a decrease in sand temperatures. Temperatures in the open zone were consistently higher than in either the border or vegetation zones and in the open zone the mean temperature only dropped below 30ºC in July. Most green turtle nests were laid in the border zone and were laid between 50-70cm deep, and so would have been exposed to temperatures between 24-28ºC throughout incubation. The data logger located at 70cm in the Border zone consistently recorded temperatures much lower than any of the other monitors; it is possible that this logger was not working correctly throughout Collection of Human Impact Data Visitors to Tortuguero The number of visitors paying to enter the CCC Natural History and Visitor Center in Tortuguero is shown in Table 14. In 2008, around 500 fewer visitors were recorded than in 2007, falling from 30,019 to 29,536; this was the second year in succession that visitation to the center decreased. The pattern of visitation throughout the year was very similar to that observed previously, with most visitors coming in January - March, with a sharp decline in May and June. The typical increase in visitation observed during July and August, which coincides with an increase in green turtle nesting, was not as significant as in recent years. 34

38 Figure 7. Mean monthly sand temperatures from June - October Mean monthly sand temperature / C June July August September October Month Veg 50 Veg 70 Border 30 Border 50 Border 70 Open 30 Open 50 Open 70 35

39 Table 14. Number of visitors to the CCC Natural History and Visitors Center Month Total x / day Total x / day Total x / day January 3, , , February 3, , , March 4, , , April 3, , , May 1, , , June 2, , , July 3, , , August 3, , , September 1, , , October 1, , , November 2, , ,025, 68 December 2, , , Total 32, , , The mean number of visitors per day in 2008 ranged from 42 (May, September, October) to 143 (March), with an average of 81 visitors per day for the year, which was almost identical to that recorded for However, February, March, May, September and December all showed a higher daily visitation rate in 2008 than in The number of people visiting Tortuguero National Park (TNP) rose in 2008, continuing the trend that has been observed since 1998 (See Table 10). In 2008, data from the Tortuguero Conservation Area (ACTo) show that 134,690 tourists were registered as paying the entrance fee to the park; an increase of almost 18,000 visitors from the figure recorded in During 2008 visitors did not pay an entrance fee to enter Barra del Colorado Wildlife Refuge. The entrance fees to TNP in 2008 generated 455,051,638 (~US$777,202) in revenue for MINAE; an increase of almost $170,000 from Year Table 15. Number of paying visitors to Tortuguero National Park, Tortuguero National Park CR visitors Foreign visitors Total visitors Barra del Colorado Wildlife Refuge Total visitors TNP and BCWF Total fees raised ,284 12,550 16,834 23,256 23,990, ,767 32,863 38,630 3,650 69,641, ,543 36,354 41,897 2,639 71,409, ,175 39,057 45,232 2,941 76,556, ,745 44,594 50,339 3,999 98,495, ,643 59,026 67, ,715, ,545 71,912 81, ,313, ,292 77,791 87, ,347,680 36

40 Year Tortuguero National Park CR visitors CR visitors Table 15. Continued. CR visitors Barra del Colorado Wildlife Refuge Total visitors TNP and BCWF Total fees raised ,257 80, , ,924, ,898 92, , ,368, , , , ,051, Capacity of hotels and cabinas The number of hotel rooms available to tourists in Tortuguero in 2008 showed a large increase from 2007, from 645 rooms to 675 rooms (See Table 16); there was a subsequent increase in the number of beds available also (from 1,399 in 2007 to 1,519 in 2008). This can be accounted for by the fact that many of the larger hotels and the smaller cabinas made extensions to their properties during Table 16. Room and bed capacity of the hotels and cabinas in the Tortuguero area Hotel / Lodge Rooms Beds Cabina Rooms Beds Anhinga All Rankin Lodge Evergreen Aracari Ilan-Ilan Balcón del Mar 6 14 Baula Cabinas Tortuguero Laguna Casa Marbella Manatus La Casona Mawamba Ella y Yo 4 8 Pachira Hostel el Icaco Samoa Meryscar 7 19 Tortuga Miss Miriam 6 9 Turtle Beach Lodge Miss Miriam # Total Hotel/Lodge 512 1,163 Miss Junnie s Hotel Princesa 8 22 Princesa del Rio Princesa Resort Taylor s Place 3 5 Tropical Lodge 9 20 Total Cabina Total 675 Rooms, 1,519 Beds Lapa Verde CCC Formerly Jungle Lodge 2 Rented exclusively to locals 3 Only available to CCC volunteer participants 37

41 In 2008 the smaller cabinas in the village accounted for approximately the same percentage of the overall room capacity as in 2007 (24.2%). Laguna Lodge is now the biggest of the hotels, with 104 rooms (20.3% of the total room capacity of the lodges). Baula Lodge changed its name again, and the Lapa Verde cabina was renting exclusively to locals Turtle tours Since 2005 the Turtle Spotter Program (TSP) has been implemented along the entire 5-mile stretch of beach (from the Tortuguero river mouth to mile 5) where tourism is permitted by MINAE. In 2008 the TSP committee was comprised of five representatives; one each from CCC, Tortuguero National Park (TNP), the Tortuguero Development Association, the Tour Guide Association and the local hoteliers. Following a suggestion from the committee after the 2007 season, a Coordinator for the TSP was contracted for Andrea de Haro (former RA and FC with CCC in Tortuguero) was hired for six months, from June November. Her role was to train the turtle spotters; coordinate the sale of brochures and provide monthly reports, and act as liaison between the turtle spotters, guides, CCC and TSP committee. In addition, 14 local turtle spotters were employed for the duration of the official green turtle nesting season (1 July 31 October). Of these 14, one was designated as the Supervisor, who assisted the Coordinator and helped oversee the other turtle spotters on the beach. The number of visitors who participated in night-time turtle tours from March - November 2008 is shown in Table 17. The Public Beach is the northern 3 3/8 miles of beach from Tortuguero river mouth to the limit of Tortuguero National Park; this part of the beach is divided into three sections for the TSP. The Park Beach is the 1 5/8 miles of beach from the limit of the National Park to mile 5, and is divided into two sections for the TSP. Visitors who participate in tours within the Park section of beach are required to have a National Park entrance ticket valid for that day. Table 17. Number of visitors participating in turtle tours in 2008 Month Public Beach # visitors Park Beach # visitors Total # visitors March x visitors / night April , May 1, , June 3, , July 8,404 5,321 13, August 9,384 5,570 14, September 5,706 1,387 7, October 4, , November Total 33,723 13,787 47, Data from ACTo N/A No tours conducted during those months 1 First permit issued 18 March - nightly average calculated for 14 days 2 Last permitted issued 6 November - nightly average calculated for 6 days 3 Calculated from 18 March - 6 November Over 47,500 visitors participated in turtle tours between 18 March and 6 November 2008 (See Table 17); this was 4,847 more than in 2007, and continued the trend observed in recent years. More than

42 twice as many people went to the Public Beach than to the Park Beach (33,723 and 13,787 visitors, respectively). Peak visitation was in August, when 14,954 visitors went on tours, with an average of 482 visitors per night during that month (See Table 17). For 2008 an average of 203 visitors per night participated in turtle tours; if this calculation was limited to the official green turtle season (1 July-31 October) the number increased dramatically to 334. The maximum number of tourists to participate in turtles tours on a single night was 768 on 6 August (Data from ACTo). Following the successful implementation of the alternative funding scheme for the TSP in 2007, during which all the expenses of the TSP were funded from the sale of information brochures that were offered to all tourists to Tortuguero, the TSP committee decided to implement the same system in The success of the brochure initiative in 2007 was presented by CCC at the 2008 International Sea Turtle Symposium in Mexico, in an oral presentation entitled Creative new funding source aids turtle conservation activities and community projects in Tortuguero, Costa Rica. There was considerable interest from delegates in the project and it was seen as a feasible model for other turtle nesting beach sites where tourism occurs. Throughout the four months of the official green turtle season (1 July - 31 October) 39,571 tourists participated in turtle tours; of these 25,200 purchased a brochure, or 63.7% of all visitors (de Haro, 2008). The percentage of visitors purchasing a brochure was less than in 2007 and this could be attributed mainly due to reluctance on the part of the local guides to support the TSP through the purchase of the brochures; of the 12,207 tourists that used local guides only 2,403 purchased a brochure, accounting for just 19.7% (de Haro, 2008). The brochures, additional donations, and the sale of t-shirts to the end of December 2008 raised a total of $104,334. This amount completely covered the expenditure for the TSP during the entire season ($72,932), which included all the salaries and benefits of the spotters, the purchase and maintenance of equipment, production of merchandise and all administration charges; leaving a surplus of $31,402. At the beginning of 2009, the TSP committee decided to use the excess funds from 2008 to construct a new tourist waiting area in sector 2, and to make alterations and renovations to the airport building (owned by CCC) for use as the waiting area in sector 1. Additional surplus funds were used to produce new brochures and t-shirts prior to the 2009 season, and to provide a cash buffer to cover program start-up expenses for the new season Artificial lights Four light surveys were conducted during the 2008 Green Turtle Program, once a month from July to October. The results from these surveys are summarized in Figure 8. As in previous years, most of the lights visible on the beach were from buildings in Tortuguero village, between miles 2 6/8-3 3/8 (See Figure 8); these included cabinas, restaurants, houses, street lights and the school. In addition, clusters of lights were also visible from the lodges located north of the village. Unfortunately a couple of lights are still visible from within the CCC station. The brightest lights remain the tall street lamps, which in the past have occasionally been shaded by the electricity company. In October of 2008, ICE (the Costa Rican Electricity Company) constructed and opened a new office in Tortuguero village; the structure included a large illuminated sign that was several metres high and that could be clearly seen from the beach at night. The majority of lights were located on the beach side of the river, although those of houses and street lights in San Francisco, and of Tortuga and Manatus lodges, were also visible from the other side of the river. As can clearly be seen from Figure 8, there are no artificial lights in the National Park due to the absence of any buildings past mile 3 3/8. 39

43 Figure 8. Summary of monthly light surveys conducted during the 2008 Green Turtle Program Tortuguero Village Average number of lights / survey San Francisco Village Tortuga Lodge All Rankin Cabinas Manatus Lodge Laguna Lodge Mawamba Lodge CCC Limit to TNP Light sources in Tortuguero village Miss Junnie s Cabinas Tortuguero School Princesa Resort Budda Beach Cafe Miss Miriam s Cabinas Miss Miriam s #2 Princesa Cabinas La Casona Cabinas Icaco Cabinas Meryscar Cabinas Balcon del Mar Cabinas Shops ICE office and sign House lights Street lights Radio antenna red light 0-3/8-1/8 1/8 3/8 5/8 7/8 1 1/8 1 3/8 1 5/8 1 7/8 2 1/8 2 3/8 2 5/8 2 7/8 3 1/8 3 3/8 3 5/8 3 7/8 4 1/8 4 3/8 4 5/8 4 7/8 Mile 40

44 3.8.5 Hatchling orientation and disorientation Turtle hatchling orientation results from the 2008 Green Turtle Program are summarized in Table 18. A total of 45 nest emergences were observed; 33 green turtle, 11 leatherback and 1 hawksbill. On average, more hatchling tracks were recorded for green turtle nests than for leatherbacks (46 compared to 20 tracks per nest, respectively). The mean angular range when outliers were excluded was 18.5º for green turtle hatchlings, 14.5º for leatherbacks and 22.0º for hawksbills (See Table 18). When outliers were included in this calculation the resulting values were 41.5º for green turtles, 42.5º for leatherbacks and 39.0º for hawksbills. Table 18. Turtle hatchling orientation observed during the 2008 Green Turtle Program Species n No. hatchling tracks x ± SD Angular range (º) x ± SD Angular range including outliers (º) x ± SD Green turtle ± ± ± 11.1 Leatherback ± ± ± 20.8 Hawsksbill One of the leatherback nests was observed during the 2008 Leatherback Program On several occasions from June - November evidence of disorientated hatchlings was recorded by researchers (See Table 19); disorientation was observed for green turtle and leatherback hatchlings. Typically the tracks showed that the hatchling wandered inland towards the vegetation, or made circles before heading to the sea. On no occasion were hatchlings found, either dead or alive, suggesting that they had presumably eventually reached the ocean. Table 19. Hatchling disorientation observed during the 2008 Green Turtle Program Date Species Mile Possible cause of disorientation No. hatchlings disorientated No. hatchlings found dead No. hatchlings found alive 19 Jun Dc 2 5/8 CCC station Jul Dc 1 4/8 Laguna Lodge Jul Dc 6/8 Tortuga Lodge Jul Dc 3 1/8 Tortuguero village lights Sep Cm 4 2/8 Unknown Sep Cm 1 3/8 Manatus Lodge Oct Cm 2/8 Unknown Oct Cm 1/8 Unknown Oct Cm 0 San Francisco village lights Nov Cm 1 3/8 Manatus Lodge Nov Cm 2 6/8 Miss Junnie s Nov Cm 3 2/8 Cabinas Vista del Mar Dc = Leatherback; Cm = Green Turtle 41

45 3.9 Environmental Education and Community Outreach Activities Environmental Education Program Numerous environmental education activities were organized by the FCs and RAs during the 2008 Green Turtle Program. The theme chosen for the different activities was Flora and Fauna of Tortuguero; several different activities were developed, for children at the school and high school, related to this central topic. Table 20 summarizes the program activities; it includes the objectives of each activity, a brief summary of the activity and the student group involved. Table 20. Summary of environmental education activities conducted during the 2008 Green Turtle Program Date Description of activity Objectives Student Group 24 Jul 31 Jul 13 Aug 19 Aug 21 Aug 10 Sep Presentation of some basic ecological concepts such as biosphere, ecosystem, community, population, species and niche. Explained to students about effects of use of pesticides on different habitats, using the case of the banana and pineapple plantations close to Tortuguero Game in which each student was a different part of the food chain and they had to interact with other elements. Game in which the students solved puzzles to learn about the characteristics of the different species of animals and plants that live in Tortuguero. Short presentation about the importance of biodiversity. Field study in which students learned how to collect data on biodiversity using quadrants. Using data collected students were taught how to create graphs using Excel. Fun game in which students made sculptures of different animals and plants. Discussion about deforestation. Students planted ornamental vegetation in the school grounds. To teach students the basic concepts of ecology. To inform students about potential contamination issues in Tortuguero. To teach students the role of different species and the important interactions within the food chain. For the students to learn the different species of flora and flora in their locality. For the students to learn the concept of biodiversity. For students to gain field experience collecting data. To teach students how to present data using Excel. To teach students about different plant and animal species. To teach students the importance of the forest for all the species who live in it. To teach students how to plant and care for trees th grade, Tortuguero school 3 rd and 6 th grade, San Francisco school 3 rd and 6 th grade, San Francisco school 9 th grade, Tortuguero school Various grades, Tortuguero school 3 rd grade, Tortuguero school

46 Table 20 Continued. Date Description of activity Objectives Student Group 18 Sep Discussion about deforestation. Students planted ornamental vegetation in the school grounds. To teach students the importance of the forest for all the species who live in it. To teach students how to plant and care for trees. Various grades, San Francisco school 24 Sep First phase of a photographic investigation of the flora and fauna of Tortuguero National Park, in which students were invited to take photographs of species of interest in the forest. To discover and study the flora and fauna of Tortuguero National Park through photograpy. For students to learn how to use a digital camera and take wildlife photographs. 8 th grade, Tortuguero high school 26 Sep Students used wildlife guides to identify the species they photographed previously. Students created a Powerpoint presentation using the photographs they had taken. For students to learn how to identify different species using keys and guides. To teach students how to make presentations. 8 th grade, Tortuguero high school 1 Oct High school students presented their photographs to the students at Tortuguero school and discussed the classification of species into Kingdoms. Pablo Elizondo (ornithologist) gave a talk about the birds of Costa Rica. Students were presented with prizes for the best photographs, and their interest or participation in the activity. To give students experience in living presentations. To teach students about the birds of Costa Rica. 5 th and 6 th grade, Tortuguero school 8 th grade, Tortuguero high school 21 Oct Game in which the students were turtle eggs and hatchlings and the RAs depicted different predators; students had to answer questions relating to each predator species. For students to learn about sea turtle biology and the threats they face at different phases of their life cycle, with an emphasis on predators. Various grades, San Francisco school 21 Nov FCs and Junior Research Assistants told a story about Archie Carr and his early work in Tortuguero. Students were asked to draw pictures to illustrate the story they heard. To teach students about turtles and their importance in the marine environment, and to explain the role that Archie Carr played in turtle conservation in Tortuguero. Various grades, Tortuguero school 43

47 Junior Research Assistant Program CCC was invited to participate in the 7 th Student Sea Turtle Symposium on 26 th July, This symposium is organized by Ecology Project International, an organization that coordinates environmental education trips for high schools students in Costa Rica and other countries. The FCs plus nine students from Tortuguero High School participated in the symposium (See Appendix 2); they attended various different activities throughout the day, and had the chance to learn how other students were involved in sea turtle conservation throughout the region. The experience at the symposium inspired the students, who approached the FCs about the possibility of presenting their own research projects at next year s event. Incorporating the wishes of the students, the FCs, in conjunction with the Scientific Director, developed the idea of a specific program for the high school students; the Junior Research Assistant Program. The objective of this program was for the students to complete a series of activities which the Research Assistants perform for CCC; this included night patrols, track surveys, nest excavations, equipment cleaning, conducting an environmental education activity at the school, and assisting in the visitor centre. They were also required to attend a series of theoretical presentations and conduct their own research project. Those students who successfully completed the list of requisite activities, and who maintained a serious, positive attitude throughout the course, received a certificate and a specially designed t-shirt upon graduation. Appendix 2 shows photographs of some of the activities of the Junior Research Assistant Program In total, 78 students participated in at least one night patrol as part of the program between 27 July and 29 October, Nine students conducted daytime track surveys or nest excavations. Six students assisted in the CCC Visitor Centre talking to tour groups about the work of CCC and helping the Visitor Centre administrator. Two research projects were conducted; the students, aided by the FCs, analyzed data collected at Tortuguero to investigate two different questions: o How has the straight carapace length of green turtles (Chelonia mydas) changed at Tortuguero, Costa Rica over the years? o Does the full moon make turtles more sensitive? The students created Powerpoint presentations that were shown to the Scientific Director and FCs in November. The students plan to also present the findings of their studies at the Student Sea Turtle Symposium in At the end of the 2008 Green Turtle Program five students had successfully completed all the requirements to graduate from the Junior Research Assistant Prorgram; Angie Abraham Myers, Kevin Abraham Myers, Marcos Corrales Bermúdez, Hazel Soza Jarquin and Indira Torres Ocampos Community Outreach Activities Veterinary Clinic Following the success of the first spay/neuter veterinary clinic in March 2008, a second clinic was conducted June, CCC was involved in the coordination prior to the clinic, and also provided logistical support during the three days that the veterinarians were working in Tortuguero. The committee had secured the donation of rabies and multiple vaccinations from the pharmaceutical company Faryvet; these vaccinations were given with preference to animals that had been previously spayed or neutered during the clinic in March. 44

48 18-20 June three veterinary medicine students from the National University gave educational talks at the schools and to members of the communities of Tortuguero and San Francisco; they discussed the importance of castration for the health of domestic animals, and gave details about the clinic. On 27 June, the results of the March 2008 veterinary clinic were presented to the tour guides of Tortuguero; there support was requested for the project, in the form of a financial donation towards materials, from the voluntary contributions made by guides to a community fund during the turtle season. Seven veterinarians attended the clinic on June; one from the Humane Association for Animal Protection in Costa Rica (AHPPA), one local vet from Cariari (Dr Hernán Barrantes Lobo), four students from the National University and one vet from the pharmaceutical company FaryVet. The vets were divided between Tortuguero and San Francisco to run simultaneous clinics in the two villages. In Tortuguero 43 dogs/cats were castrated and 34 animals received vaccinations; in San Francisco, 20 animals were castrated and 27 were vaccinations. These figures make the total for 2008, 156 castrations and 61 vaccinations. CCC provided food for the students giving the educational talks, and also for the vets based in Tortuguero during the clinic. In addition, the Scientific Director, FCs and RAs provided logistical support to the vets in Tortuguero as needed. A third clinic planned for November 2008 was cancelled due to inclement weather Independent Research Projects The two independent research projects conducted during the 2008 Green Turtle Program were successfully completed and provided some interesting data about the impacts of tourism on turtle nesting behavior and hatching success. The results of these investigations were presented at the 2009 International Sea Turtle Symposium in Brisbane, Australia February, 2009, in a poster entitled Do tourism activities affect green turtle (Chelonia mydas) nesting behaviour and hatching success at Tortuguero, Costa Rica? (See Appendix 3) Impact of tourist presence on the nesting behavior of green turtles The student, Catalina González Príeto, worked in close liaison with the Turtle Spotter Program to encounter turtles with tourists present during the nesting process; all of the spotters and guides were very helpful during the data collection phase of the study. The 2008 Green Turtle Program RAs assisted in the collection of data for the project; to ensure that the sample size was sufficiently large enough to make valid scientific analyses. A total of 85 females were observed for the study. The number of people observing a single turtle ranged from Individuals were assigned to one of three categories depending on the number of people present during the nesting process; No impact turtles that were observed only by 1-2 researchers, Low impact turtles observed by people or High impact turtles observed by people. Of the 85 females observed, 31 were classified as No impact, 24 Low impact and 31 as High impact. Four females were excluded from the subsequent statistical analyses to compare the duration of the different phases of the nesting process between the three impact categories; two 45

49 because they did not complete all phases of the nesting process and two others because the time they spent disguising the nest site was outside the range of values observed for other females within the same impact category. Table 21 shows the mean duration of the different phases of the nesting process calculated for turtles in each of the three impact categories. There was considerable individual variation in the time spent on the different phases of the nesting process; oviposition, for all three impact categories, ranged in duration from minutes, covering ranged from minutes and disguising the nest site ranged from minutes. Typically, green turtles spent longest disguising the nest site than for the other nesting behaviors measured in this study. No significant difference was ob][=served between the three different impact categories for the time spent in oviposition or covering (p = and p = 0.199, respectively), but there was a significant difference observed for the time spent disguising the nest site (p = 0.012). A subsequent Fisher LSD test revealed that this difference was between the No impact and the Low and High impact categories; if turtles were observed by more than 10 people during the latter part of the nesting process they spent significantly less time camouflaging than turtles with no people present. Table 21. Duration of different phases of the nesting process for turtles subject to different levels of tourism impact Impact N Duration of Phase of Nesting Process / x min ± SD Category Oviposition Covering Disguising No impact ± ± ± Low impact ± ± ± High impact ± ± ± Effect of nest trampling on the hatching and emerging success of green turtle nests Luis Gonzalez, the undergraduate student, collected the data in conjunction with the FCs and RAs to conduct an investigation into the effect of nest trampling on hatching and emerging success in green turtle nests. A total of 26 pairs of green turtle nests were marked from 16 July - 19 August, 2008; one of each pair was a control nest, with no trampling, and the other was an experimental nest, subject to trampling twice a week throughout the incubation period, up to day 50. Of the 26 pairs of nests, 12 of the experimental nests were classed as Low impact and 14 were classed as High impact. The Low impact nests had the equivalent of 40 people walking over the nest per week and the High impact nests had the equivalent of 200 people. A Wilcoxon signed-rank tests for paired samples was used to compare the hatching and emerging success between the control and experimental nests. Only undisturbed nests were included in this analysis and so several nests were excluded; three were disturbed by other turtles that nested at the same location, three had new nests laid very close and so could not be excavated without disturbing the new nest, one nest was depredated, one was invaded by roots and one was mixed with a hawksbill nest. Results of the analyses revealed that there was no significant difference in hatching or emerging success between pairs of Control and Low impact nests (p = and p = 0.556, respectively) or between pairs of Control and High impact nests (p = and p = 0.323, respectively). Other possible effects of nest trampling were considered by examining the number of deformed embryos the number of pipped eggs encountered in the nest during excavation (eggs are categorized as 46

50 pipped when the shell has obviously been broken by the hatchling inside but for whatever reason it has failed to emerge from the egg). Only five deformed embryos were found, three in experimental nests and two in control nests, thus no analysis could be performed. A total of 26 pipped eggs were found in Experimental nests (both High and Low impact nests) and 44 in the Control nests (22 of which were found in a single nest); no significant difference existed between nests that had been subjected to trampling or those that had not. 4. Discussion 4.1 Preparations The training and orientation program given to the RAs by the FCs is essential for them to learn the monitoring protocol in detail, and to give them the opportunity to practice various important skills, such as tagging, carapace measurements and nest marking. Even for RAs with previous experience working with sea turtles these theoretical and practical sessions ensure that everyone collects data according to the CCC protocol. In future years care should be taken to make sure that all RAs receive sufficient practice and supervision in tagging during the first few weeks at the station, since there were a couple of RAs in 2008 that had high tag loss which could have been the result of poor technique or lack of training. It is suggested that throughout the program the FCs work with all of the RAs on a regular basis to provide continuous training and supervision, to correct any bad practices that are observed and to evaluate the data collection of the RAs. The change to the orientation program in 2008; to extend it from one to two weeks and to incorporate different talks and activities that gave a more well-rounded introduction to Tortuguero and the community, was definitely beneficial and none of the RAs commented on a lack of information or insufficient training in their evaluations. Regular group activities, designed to develop good dynamics amongst the RAs helped to maintain a good relationship in the group. Fortunately the majority of the beach markers placed at the start of the 2008 Leatherback Program were still in excellent condition at the start of the 2008 Green Turtle Program and so the RAs were limited to replacing an occasional missing marker and repainting those still in place. This activity, though somewhat time consuming, is important as it provides the opportunity to teach the RAs the need to familiarize themselves with the beach and the markers to facilitate the night patrols. For future years it might be worth investigating the possibility of using reflective paint or tape for the beach markers to assist with finding them at night. 4.2 Track Surveys During the 2008 Green Turtle Program a new track surveyor was contracted to replace the new surveyors that had been employed during the 2008 Leatherback Program. The track surveyor position is an important one, and care needs to be taken when selecting and training the person. The new surveyor has worked for several years as a spotter for the Turtle Spotter Program, and thus has considerable knowledge of how to identify turtles from their tracks, and also experience walking the beach in adverse conditions. The FCs and Scientific Director were involved in his training, both on the beach and also with regard to correctly completing the data sheets at the end of each survey. To avoid some of the problems encountered in previous years, which resulted in the loss of data, a new protocol was established with the FCs responsible for receiving the completed data sheets immediately after each survey is completed. 47

51 4.2.1 Green Turtles Green turtle nesting was observed from February to November, with two obvious peaks in nesting; one in late-july, the other larger peak in late-august/early September, when over 2,000 nests were observed in a single night (See Figure 1). Unfortunately several weeks of track survey data were lost (for the period from October to mid-november). Over 100,000 green turtle nests were estimated to have been laid during 2008 season, which was lower than in However, the 2007 season was exceptionally high, and so it was not surprising to observe a decline the following year; a similar pattern was also observed in 1993/1994 and in 1998/1999, in which a high year was immediately followed by a low year (See Figure 2). It will be interesting to observe the green turtle nesting trend over the next few years to determine if the positive increase observed since the 1980 s continues. In 2008 green turtle nesting between the Tortuguero river mouth and the mile 5 marker represented 17.4% of all nesting for this species between the river mouth and Jalova lagoon; this is slightly less than the percentage observed in The overall spatial distribution along the beach was also quite unusual, with an obvious increase in nesting density noted after mile 4; there was no distinct peak in the centre of the beach (around mile 9) has seen recorded in previous years. The daily track surveys conducted by the FCs and RAs from June - November between the Tortuguero river mouth and the mile 5 marker require considerable effort but provide invaluable data relating to spatial and temporal nest distribution. While they were originally initiated in 2004 as a means of evaluating the effectiveness of the Turtle Spotter Program in minimizing negative impacts of tourism on turtles, they should be an integral part of the monitoring protocol as they also give a detailed record of the level of illegal take of nesting females and eggs, and also an indication of the extent of dog predation of nests. Over 18,000 green turtles were laid in the first five miles of the beach, and more than 17,000 false crawls were recorded; successful nesting was recorded in 51% of emergences. Of these, nesting within the limits of Tortuguero National Park accounted for 55% of all nests (for the first five miles), which was slightly more than in Results from the daily track surveys over the last five years should be analyzed to determine if there has been an increase in the percentage of successful nesting emergences that could be attributed to better control of tourists on the beach at night through the Turtle Spotter Program. It would also be interesting to see if there has been a distributional shift in nesting along the entire beach over the last few decades. Due to the numbers of green turtles nesting in Tortuguero the surveys depend entirely on the visual assessment of the nest site to determine if the emergence resulted in a nest or a false crawl; obviously such a protocol relies on the capabilities of the surveyors in differentiating between nests and false crawls and is subject to observer errors. It would be relatively easy to ascertain the degree of error in the results by conducting a validation experiment; for a selected subsample of nests, a search could be made to locate the egg chamber once the researchers have made their evaluation based on the visual inspection of the nest site alone. The presence or absence of eggs would either confirm or refute their original decision and so provide a margin of error estimate for the surveys. On only two occasions during the weekly track surveys in 2008 was the illegal take of turtles or nests reported. This, however, definitely underestimates the level of illegal poaching that occurred during the year, as evidence of poached nests or turtles was frequently observed during the daily surveys of the northernmost five miles of beach. It should be stressed to the weekly track surveyor that they carefully look for and record any signs of illegal take of fresh nests or turtles. Results from the daily 48

52 track surveys revealed that green turtles and nests were regularly taken from the northern five miles of beach throughout the 2008 Green Turtle Program (See Figure 6); 276 nests (1.6% of all those laid) and 34 females were taken between June - November. Poaching of both nests and females was higher in 2008 than in 2007; although the pattern of illegal take was similar in both years, with a peak close to the Tortuguero river mouth. It was also disturbing to see a sharp rise in poaching just within the limits of the National Park, showing that those involved in this activity have no respect for the protected area, or the laws regarding seas turtles. Once again in 2008 MINAE complained of very limited resources and insufficient personnel to conduct patrols or provide adequate enforcement of the laws. As in previous years CCC should prioritize the need to secure additional resources for MINAE to allow them to protect the natural resources of Tortuguero National Park, with specific focus on turtles and their nests. Furthermore, other enforcement agencies, such as the police or the Coast Guard, should be approached for assistance in reducing human threats to turtles in the region. Jaguars continued to predate turtles in 2008; weekly track surveys recorded 23 females killed within the park; of which one was a hawksbill. As observed in other seasons the percentage of females taken by jaguars is insignificant and they do not pose a grave threat to the nesting population; however, it is worth noting that on one night five turtles were killed, suggesting that jaguars are not preying on turtles for food, but maybe simply attacking them for sport, or to train their young how to hunt. Further investigation is warranted to elucidate the details of the green turtle-jaguar interaction Hawksbill turtles During the weekly track surveys of the entire nesting beach just six hawksbill nests were observed in 2008; however, the daily track surveys of the northern five miles recorded 21 nests and 17 false crawls. Unfortunately the low density of hawksbill nesting is not easily detected by weekly surveys, and so it is useful to have the data from the daily surveys with which to compare. From these surveys it would appear that hawksbill nesting has shown a slight increase in the last few years, which is very encouraging for this critically endangered species. It was very encouraging to see that on one night in July three hawksbill nests were recorded within the northern five miles of beach; such data highlight the value of the daily track surveys in providing detailed information about this species that could be missed during the weekly surveys Leatherback turtles Whilst a comprehensive discussion of leatherback nesting at Tortuguero in 2008 can be found in Debade et al. (2009), it was disappointing to observe that the slight increase in leatherback nesting recorded in 2007 did not continue in However, communication with other nesting beaches along the Caribbean coast of Costa Rica and Panama suggested that, at other locations, leatherback nesting in 2008 was high. It could be, therefore, that females are shifting their nesting beach use away from Tortuguero. 4.3 Tagging of Nesting Sea Turtles Green turtles The goal of 1,000 newly tagged green turtles was successfully achieved in September Whilst tagging efforts were obviously focused on the peak of the season, to ensure that 1,000 new females were tagged, new turtles were also tagged throughout October in In previous years tagging has stopped in September; however, due to the large number of turtles without tags (n = 611) that were reported in October 2007 it was decided to continue tagging until night patrols were suspended at the 49

53 end of October These late nesting females might provide some additional insight into the nesting behavior of green turtles at Tortuguero; with regard to the size of individuals, or the number of eggs being laid. Just over one quarter of all the individual females observed in 2008 were previously tagged (n = 524); this was considerably lower than the number observed in These encounters are very important for they allow the estimation of between season tag loss and also annual survival probabilities. The number of turtles that had originally been tagged more than 10 years previously was high in 2008; of the 524 females 96 (18.3%) were first seen in Tortuguero more than a decade earlier. Furthermore, seven females were first tagged over 20 years previously. A new nesting record was established for the project in 2008, with the return of two green turtles that had originally been tagged in 1980, 28 years ago. This increase in the number of older females returning to nest is encouraging, as it suggests that their annual survival rate is high, and that they are managing to avoid the numerous threats that they face during migrations and on their feeding grounds away from Tortuguero. This observation, compounded by the fact that there continues to be a very high proportion of untagged (and possibly young) females nesting each season is indeed encouraging, as it indicates a healthy mix of age classes in the nesting population. If the encounters showed a high percentage of only old tagged or only untagged females it would worrying, as this would imply that there was a deficit of either young or old individuals nesting at Tortuguero. Each year several green turtles are encountered with tags from other nesting beach projects; in 2008 there were 22 females with tags from Cano Palma (the research project just north of the Tortuguero river mouth), Mondonguillo and Pacuare. As other monitoring projects become established along the Caribbean coast of Costa Rica the information about the frequency with which green turtles move between different beaches will become more widely available. While known to have strong site fidelity to their natal beach, the evidence from Tortuguero in 2008 suggests that there is limited movement between nesting sites and that, like the leatherback, green turtles can even move between different countries (evidenced by two turtles encountered with tags from Panama nesting beaches). Another interesting tag observed in 2008 had a return address for Cuba. The Scientific Director was able to contact turtle researchers in Havana and received the original tagging data; the turtle was tagged in-water on a feeding ground in 1997 and from her size was classified as an adult female. At the same time the Scientific Director also received information about the individual whose tag was recovered from a turtle killed by a jaguar in This female had been tagged at the same feeding ground off the coast of Cuba in 1991; though at the time her size did not warrant classification as an adult. The recent increase in the prevalence of in-water projects based at feeding grounds around the Caribbean will begin to provide valuable data about the age to sexual maturity for different sea turtle species in the region, as more sexually mature females are intercepted on nesting beaches. Continued cooperation at the regional level is critical to allow such data to be shared among projects and utilized to further improve protection measures for sea turtles in the Caribbean and beyond. Unfortunately overall within-season tag loss was very high in 2008, at 6.8%. This could be attributed to several individuals within the research team who consistently had turtles return with a tag missing. It highlights the need for the FCs to ensure at the start of the program that everyone receives adequate training in the correct tagging technique. Continuous supervision, especially for those who can be seen to have some difficulties, is also very important. Obviously, at the start of the Green Turtle Program nesting density is often quite low for the first weeks, during the training period, and often it is difficult for the FCs to have sufficient turtles available for them to assess each RA individually on more than one occasion. In such situations in future the supervised training patrols should be continued, until the FCs are confident that everyone is competent at tagging. 50

54 A tool to improve training would be to produce a bilingual video that could be shown to all RAs during their training period; this video could provide a step-by-step guide to the tagging process (for both hard-shelled species and leatherbacks). In addition, it could also include detailed instructions on other activities in the monitoring protocol including carapace measurements and nest marking Hawksbill turtles The number of hawksbill encounters in 2008 (n = 13) was higher than in 2007 (n = 11), continuing the trend observed in the last few years. It was encouraging to see that of the 11 individuals observed, two had tags from several years ago (1998 and 2001), and that two females were seen more than once during the 2008 Green Turtle Program. It was also interesting to observe a mini peak in hawksbill encounters towards the end of night patrols in October. Given the low nesting density of this species at Tortuguero it is important that all RAs realize the importance of every encounter with a nesting hawksbill during night patrols as they provide very valuable information on the species. Following a request from the Scientific Director to the committee prior to the start of the Turtle Spotter Program in 2008, a decision was made to not show hawksbills to tour groups (if a green turtle was available). This decision was taken with the aim of eliminating any possible negative impacts that the presence of tourists could have on the female, and also giving priority to CCC researchers to collect data on the nesting behavior of this species Leatherback turtles Debade et al. (2009) includes a detailed review of the tagging of leatherback turtles at Tortuguero in However, it is worth noting that leatherback nesting was observed for more than a month of the 2008 Green Turtle Program; four different females were encountered, the last on 13 July. It would be interesting to analyze the temporality of leatherback nesting at Tortuguero (and throughout the Caribbean coast of Costa Rica and Panama to include the entire population of which Tortuguero is a part) to assess whether there has been a shift towards nesting later in the season over the years. 4.4 Biometric Data Collection Green turtles The overall mean curved carapace length (CCLmin) was 105.3cm and the mean straight carapace length (SCLmax) was 99.0cm. These measurements are consistent with those obtained from the Tortuguero green turtle population in previous seasons. In addition, the mean clutch size of 111 eggs was very similar to that determined in other years. Research Assistants showed a greater degree of precision that volunteer participants for both CCLmin and SCLmax measurements, that would indicate that the training provided by the FCs at the start of the program was effective, although care should be taken to ensure that the volunteer participants are adequately supervised during the collection of carapace length data. There was considerable variability in the measurements taken of the same female when she was observed on more than one occasion, and so care should be taken during the training sessions to ensure that everyone is measuring the carapace in the same manner, using the same start and end points. As seen in previous years the SCLmax showed a higher precision than the CCLmin measurements and it is suggested that this measurement continue to be taken for females nesting at Tortuguero. The SCLmax should be recorded in addition to the CCLmin for each female, as many nesting beach 51

55 projects do not take the SCLmax, and so the data from Tortuguero would not be comparable if this was the only carapace measurement taken Hawksbill turtles Carapace measurements obtained for hawksbill turtles during the 2008 Green Turtle Program were within the range observed in previous years, and both CCLmin and SCLmax were more precise for hawksbills than for green turtles, which is the reverse of what has been observed in the past. The mean clutch size for hawksbills was similar to that determined in other years (152 eggs), and is well within the known range for this species in the Caribbean region Leatherback turtles Debade et al. (2009) contains information about biometric data collection from leatherback turtles nesting in Tortuguero during the 2008 Leatherback Program. For those individuals observed during the 2008 Green Turtle Program the mean carapace length (CCLmin) was slightly larger than that calculated for earlier in the season (152.2cm compared to 150.3cm, respectively), although the sample size was obviously much smaller. It would be interesting to analyze the size data to determine if there is any temporal variability in size of individuals arriving at different times during the nesting season. The mean clutch size of leatherbacks nesting later in the season appeared to be smaller than that for females nesting during the peak season for this species (61 eggs compared to 72 eggs, respectively). It is possible that there is a decrease in clutch size over the course of the nesting season; data collected since the start of the Leatherback Program in 1995 could be analyzed to determine if there is a seasonal decline in clutch size. 4.5 Fibropapilloma Assessment Of the sample of green turtle females specifically examined for the presence of fibropapilloma tumors in 2008, only 1.6% was reported to have tumors. This is consistent with the prevalence of the disease recorded in previous years. It would be extremely helpful to photograph possible fibropapilloma tumors for positive identification purposes; this is something that could be included in the monitoring protocol and research permit for future years. It would also be interesting to conduct a more in-depth health assessment of the nesting population of green turtles at Tortuguero with particular emphasis on the presence of diseases such as fibropapillomatosis. Fibropapilloma is definitely present in the green turtle population nesting in Tortuguero, and in 2008 one female was observed with a tumor on her cloaca, which could ultimately restrict her ability to lay eggs effectively and result in considerable complications. It is important to continue to monitor the presence of this disease in future programs, and to pay particular attention to the training of RAs in its identification, so that any real increase in its prevalence can be monitored immediately. 4.6 Determination of Nest Survivorship and Hatching Success Green turtles A total of 145 green turtle nests were marked during the 2008 Green Turtle Program, which is fewer than in some previous years. However, of these 134 were monitored on a daily basis and the fate of the nest was accurately determined upon excavation. Greater emphasis was placed on the daily inspection of nests during 2008, to reduce the number of nests for which the fate could not be ascertained. In addition, to help identify the nest at excavation, a short piece of flagging tape was placed in the nest chamber at the time of oviposition; this tape had the nest code written on it. This 52

56 provided a guarantee that the nest being excavated was indeed the nest originally marked; this is especially helpful in sections of the beach where nesting density is high, and there is a greater potential for another turtle to have disturbed the marked nest during the incubation period. On occasion this tape was found outside an empty egg chamber that showed evidence of having been poached; the tape provided further proof that indeed the eggs had been taken. It is suggested that this practice be continued in future Green Turtle Programs to aid with the identification of nests during excavation. In 2008 only six nests could not be encountered at the time of excavation, and no flagging tape was found either. While it was encouraging to see that over 70% of nests remained undisturbed during the incubation period, it was unfortunate that the highest loss of nests was as a result of poaching. It appeared that nests were being taken up to several days after they were laid, and that those responsible were aware of the monitoring schedule and were visiting the beach after the morning nest check and track surveys were completed by the FCs and RAs. Considerably fewer nests were disturbed by dogs in 2008, however, and this could be a reflection of a greater control by dog owners over their animals during the nesting/hatching season, or simply that dogs were not disturbing the fresh nests and so the levels of predation were not detected during monitoring activities. Overall hatching and emerging success of marked nests was high in 2008, 84.1% and 80.7%, respectively; this is within the range observed for green turtles at Tortuguero previously. Emerging success was affected by one nest that was inundated following eclosion of the hatchlings; 125 dead hatchlings were recorded during the excavation. This nest was laid at the end of September and so was subject to high rainfall during the incubation period and also high tides during November. In future it would be interesting to study the changes in beach dynamics during the nesting season, to ascertain whether hatching success of nests in certain sections of the beach and at certain times of the season could be correlated with environmental conditions and beach stability. The same pattern of nest site selection was observed in 2008 as in previous years, with the majority of green turtles choosing to lay their eggs in the border zone; these nests would be subject to partial shading during the day and a range of sand temperatures between C (See Table 13). It is likely therefore that those nests would be producing a higher percentage of male offspring than female Hawksbill turtles Only five hawksbill nests were marked during the 2008 Green Turtle Program. Hatching success was high (77.9%) as has been observed previously at Tortuguero for this species. Emerging success however was only 50.9%; this was influenced by two nests in which a large number of hatchlings were observed during the excavation. One nest had 78 dead hatchlings within the egg chamber; this nest was located in front of the Tortuguero airport (at mile 6/8) and it was observed by the FCs and RAs that some of the heavy machinery that was being used to resurface the landing strip had been out on the beach, and had passed directly over the nest. This incident was reported to MINAE officials in the hope that they would reprimand the contractors responsible for the construction work; however, it is not thought that the company received a formal complaint from MINAE. It is hoped that the new policy to not show hawksbill turtles to tour groups will allow CCC personnel greater access to these females, and that in future more nests will be marked and followed during the incubation period, to gain a further insight into the survivorship and hatching success of this species at Tortuguero. 53

57 4.6.3 Leatherback turtles A discussion of leatherback nest survivorship and hatching success in Tortuguero during 2008 can be found in Debade et al. (2009). 4.7 Physical Data Collection Rainfall The pattern of precipitation observed in 2008 was similar to that observed in other years, with very high rainfall in June; July and August, were also very wet months. September was very dry and then rainfall increased in October and November was the wettest month. It is hoped that the physical data collected by CCC at Tortuguero for at least the last ten years can be analyzed to determine any potential changes in environmental conditions in the regions; such conditions could have impacts on the nesting behavior for turtles and also on the survivorship and hatching success of nests laid on the beach Air temperature The air temperature data recorded during 2008 reflect the pattern of rainfall observed during the Green Turtle Program; August and September were the warmest months and in November the temperature dropped. The range of temperatures observed (20-31 C) was consistent with those from other seasons in Tortuguero Sand temperature Unfortunately there were several problems with the data loggers during 2008; one stopped working in April (Border 70cm); although it was replaced in July the subsequent data collected were consistently lower than the other data loggers in that zone and so it is possible that it was working effectively. For several others (Vegetation 50cm, Border 30, 50 and 70cm) problems were encountered when downloading the data in October. Another data logger (Vegetation 70cm) stopped working between July and October and the data could not be retrieved. All of the Open zone data loggers were lost after October 15; this was possibly due to exceptionally high tides observed in November eroding the beach where they were located. Obviously this represents not only a financial loss but also a loss of important data. In future care great care must be taken when choosing the location for the data loggers on the beach, to select a site which is typically not affected by tidal erosion. Furthermore, if high tides are observed for extended periods, the location of the data loggers should be checked on a daily basis to ensure that they have not been exposed by tides. If this happens they should be removed, the data downloaded and the loggers stored until beach conditions improve and they can be relocated in a different stretch of beach. As mentioned above, sand temperatures will be influenced by the level of rainfall, and the precipitation experienced in 2008 was observed to directly effect the sand temperature (See Figure 7). Sand temperatures ranged between C; as in other years, the open zone was more susceptible to higher temperatures than either the border or vegetation zones. And the deeper data loggers showed more stable (though lower) temperatures. In 2008 green turtles at Tortuguero are depositing their eggs between 50-70cm and so they are subject to sand temperatures between C; these temperatures are below the recorded pivotal temperature for this species and so it is likely that the majority of hatchlings produced were likely to be male. And, as for the monitoring of rainfall and air temperature, the collection of data on sand temperatures 54

58 from the Tortuguero nesting beach is an important component of the protocol, and should continue in future programs. 4.8 Collection of Human Impact Data Visitors to Tortuguero The decline in visitation to the CCC Visitor Center observed in 2007 continued in 2008; around 500 fewer visitors were received than in the previous year. One possible reason for this is that several of the hotels and tour operators have copies of the CCC video and show it to their guests either en route to Tortuguero or at the lodge, so the need to visit the center is negated. To overcome this problem a new video is needed, with updated information about the work of CCC, and it should not be made available for public sale. In addition, while funding is unavailable to make necessary structural changes to the Visitor Centre, some adjustments to the displays and current information available to tourists are urgently required. This could include temporary displays with themes that change throughout the year; for example, information about the different species nesting at a given time, or threats to hatchlings. Tortuguero National Park continues to show an increase in annual visitation; in 2008 over 134,000 tourists paid the entrance fee to the park, generating revenue in excess of $777,000. With such high numbers of tourists visiting the area, it is vital that CCC maintains the close relationship with TNP and MINAE staff, to ensure that such high levels of visitation do not negatively impact the natural resources of the region, with specific interest, or course in the turtles nesting on the beach, and using the near-shore waters protected within the park limits. Unfortunately during 2008 very little presence of park guards was observed on the beach, either during the day or night. This lack of patrols resulted in a high level of poaching during the year, with more nests and turtles being taken than in Reduced presence of enforcement personnel on the beach definitely appeared to be a factor in the increased illegal take in Capacity of hotels and cabinas The capacity of hotels and cabinas in Tortuguero fluctuates between years, as establishments increase the number of rooms or are closed for refurbishment for extended periods. However, it would appear that several of the hotels increased their capacity in 2008, with the number of available rooms rising to 675, equating to over 1,500 beds per night. Almost a quarter of this capacity is within the smaller family-run cabinas in the village that cater for the independent traveler rather than the package tourists who typically visit the lodges. CCC needs to continue to monitor the growth of tourist establishments in the area, to provide a baseline of information about development in the community Turtle tours Turtles are one of the main reasons why many visitors come to Tortuguero; thousands of people are attracted to TNP each year with the expectation of witnessing a turtle nesting on the beach. Over 47,500 people paid to go on turtle tours in 2008; with 768 tourists recorded on the beach one night in August. While the Turtle Spotter Program (TSP) is able to effectively control the tour groups, and definitely limits the impacts that such numbers of people are having on the nesting turtles, there has to be some limit to the number of people permitted each night. What was very evident in 2008 was that there were still many occasions when there were several tour groups around the same turtle (See section and for results and discussion of the study to investigate the effect of tourists on turtle nesting behavior). The TSP committee needs to address this issue, and it needs to ascertain the maximum number of tourists that can be accepted each night, and be rigorous in not surpassing this limit. The objective of the TSP is to minimize negative impacts of tourism, one of which could be the 55

59 sheer volume of tourists around a single female, even if the groups are organized and coordinated effectively by the spotters. CCC must be insistent that a study to determine the carrying capacity of the beach is determine; such studies have been conducted to set limits for the trails and the canals in TNP, but not for the beach. This is a serious shortcoming on the part of MINAE and needs to be addressed urgently prior to the start of the 2009 season. The employment of a coordinator for the TSP in 2008 was extremely useful, and was of considerable benefit to the program and of assistance to CCC in its administration. This person oversaw the training of the spotters (with support from the Scientific Director and FCs), coordinated the daily implementation of TSP activities, and supervised the data relating to the sale of the brochures and other merchandise. They also acted as an on-site liaison between TSP personnel, park staff, tour guides, CCC researchers and the TSP committee members based in San Jose; it is strongly recommended that this position continue in future. The new funding system for the TSP continued to be successful, with more than $100,000 raised in 2008 through the sale of brochures. Once again this money was more than sufficient to cover the operating costs of the program. Before the start of the season the excess funds from 2007 were used to consolidate the program infrastructure with the construction of two new tourist waiting areas in the National Park. These areas greatly increased the comfort of the tour groups waiting in sections 4 and 5, as in previous years they had to sit on logs in the forest or under a temporary awning; neither of which provided adequate shelter from the tropical weather often experienced in Tortuguero. Unfortunately the percentage of tourists who purchased the brochure was lower in 2008 than in 2007 (63.7% compared to 70.6%); this decline can be directly related to the lack of support by the local guides because while the majority of lodge guests receive a brochure within their package, the local guides are not purchasing brochures for their tourist. It is frustrating to observe this unwillingness to cooperate with mechanism by which the TSP is funders, as all of the guides are receiving the benefits of the TSP on the beach. During 2008 several methods were used to try and encourage the local guides to participate, including an agreement between guides and the National Park by which they would be recommended to tourists if they supported the program. A priority of the TSP committee in 2009 will be to work with the local guides, via the tour guide association in Tortuguero, to formalize strategies in which they improve the percentage of guides purchasing brochures for their tour groups. The TSP is definitely having a positive impact on the turtle population on Tortuguero, and also the community; in 2008 more spotters were contracted giving seasonal employment to more local people. Obviously, there are still some aspects of the program that need further development and improvement, but in general there is an overall agreement among the different stakeholder groups that the TSP is beneficial to everyone and must continue to be implemented in coming years. It is also very important that CCC remain actively involved in the overseeing of the program, to ensure that the needs of the nesting females remain the central focus of TSP activities, and that they are not overshadowed by the economic benefits that tourism can provide Artificial lights Unfortunately the issue of light pollution in front of the village, and near to several of the lodges continued throughout The lack of apparent awareness of the potential problem caused by artificial lights on the nesting beach was highlighted when the national electricity company (ICE) erected a large illuminated sign in the village towards the end of the nesting season that could be clearly seen from the beach. In 2009 efforts must be made to improve the situation in the village, and also in front of the lodges that are located away from the community. One way in which awareness about this issue could be raised is by informing the community about the 56

60 marked increase in the number of disorientation events witnessed in 2008; all of which could be related to a specific light source. Hopefully by making people aware of the problems that artificial lights create for turtles, especially for hatchlings, but that the solutions are very simple and inexpensive, there is great possibility for the problem to be greatly reduced in future Hatchling orientation and disorientation There was a considerable number of hatchling disorientation events observed in 2008; 12 compared to just two in Almost all of these events could be directly related to a specific known light source behind the beach, including, unfortunately, the CCC station. It would be worthwhile approaching the owners/managers of the lodges or cabinas indentified to explain to them the problem that their lights are creating for hatchlings emerging in front of the unshaded light sources on their properties. 4.9 Environmental Education and Community Outreach Activities Environmental education program The commitment of the FCs to the environmental education program during 2008 was reflected not only in the number of activities that were carried out, but also in the scope and focus of these activities. In an effort to not saturate the local students with information about sea turtles, the FCs and RAs chose the topic of Flora and fauna of Tortuguero as the central theme during the 2008 Green Turtle Program. The concept was to provide the local children with a greater understanding and appreciation for the species that exist within TNP, and that all the plants and animals need to be protected. There was very active participation by all the RAs, as well as the ornithologists that are periodically based at the CCC station. The range of activities was such that the students remained enthusiastic and actively participated. They were taught new skills and hopefully gained a greater awareness of the environment in which they live. The idea of the Junior Research Assistant Program was developed following the participation of several high school students at a regional student symposium on sea turtles. The FCs and the Scientific Director used the enthusiasm that visit generated in the local youth to create a program specifically for them, which had them working side-by-side with the RAs and gaining a more in-depth understanding of the work involved in turtle research and conservation. Many students were keen to be part of the program, but few were able to make the necessary level of commitment to complete all of the requirements to graduate; only five alumni received a certificate and t-shirt at the end of the course. However the number of students who graduated was not the best measure of the program s success; what it generated was a much closer interaction between the FCs, the RAs and the younger members of the Tortuguero community. Including the people of Tortuguero in the work of CCC has been important since Dr Archie Carr first began his research efforts in the 1950 s; indeed it is vital to the success of the program. Such an initiative as the Junior Research Assistant Program will foster links with the youth of Tortuguero that will hopefully have positive benefits for many years to come. The program will definitely be continued in future years, and it is planned to expand the scope of the activities, to maybe even incorporate National Park personnel to provide the students with an insight into the work of the park rangers Community outreach activities Veterinary clinic The second veterinary clinic held simultaneously in Tortuguero and San Francisco in June was extremely successful; more than 60 animals were spayed/neutered bring the total for the year to over 150. It was very pleasing to observe the support of the two communities; almost all of the animals were bought to the clinic by their owners for treatment. In addition, the program received backing 57

61 from a national pharmaceutical company who donated vaccinations. The problem of the overpopulation of dogs is not going to be solved rapidly, however, the veterinary clinics, in conjunction with an education campaign are an important first step towards a solution. Hopefully the clinics can be continued at regular intervals in future years, to ensure that the dog population does not increase, and ultimately starts to decline, so reducing the threat to the turtles in the region Independent Research Projects Data collection for two independent research projects was conducted during the 2008 Green Turtle Program, both of which were concerned with the impacts of tourism on sea turtles in Tortuguero. These studies were very important, as they provided information that could be used to demonstrate the potential negative effects that tourists could have on both female nesting behavior and also the ultimate hatching success of the nests laid. It was hoped that the findings could be used to assist with decisions made regarding the activities of the Turtle Spotter Program. The study looking at the effect of tourist presence on the behavior of nesting green turtles had great support from the spotters and the tour guides, many of whom were very interested to know the results of the research. The findings were very interesting; firstly because they showed that many turtles were observed by numerous tour groups, with up to 84 people recorded around a single female, and secondly because they found a significant difference in the amount of time that the female will spend camouflaging her nest if she is observed by more than ten people (which equates to one maximum size tour group in Tortuguero). That more than 80 people were close to a single turtle is worrying and seems to go against all that the TSP works for with regard to limiting the impacts of tourism on the nest beach. Even if all the groups are effectively managed by the spotters around the turtle there are still some serious issues to be addressed with regard to this quantity of people that are allowed to be together with one female. More disturbing is the fact that the females are altering their behavior depending on the number of people close to them. A reduction in the time the turtle spends camouflaging the nest site could result in reduced survival or lower hatching success for several reasons: If less sand is on top of the eggs they could be subject to higher levels of predation as they are more easily encountered by predator species digging in the sand The microclimate within the egg chamber could be altered, with greater temperature fluctuations during the incubation period, or a change in the process of gas exchange around the eggs. The nest could suffer more from the effects of people walking on top of the egg chamber. This study should be conducted at least in one other season, with the protocol modified to mark the nest at the time of oviposition and monitor it throughout the incubation period to assess survivorship and also determine hatching and emerging success by excavating the nest after the hatchlings have emerged. Such additional information would greatly improve the study and is necessary to ascertain whether the observed behavioral changes resulting from the presence of lots of people during the nesting process could have tangible negative impacts on the survival and success of the nest. It is hoped that the study can be repeated in The project that investigated the impact of trampling on nest survivorship and hatching success followed a rigorous protocol to try and ensure that the results obtained could be correlated to the level of trampling and were not simply due to the environmental or spatial conditions of the nest. The study was logistically quite difficult, and required considerable effort on the part of the student, the FCs and the other RAs. It was quite surprising to observe that there was no significant difference in survivorship or hatching success between nests that were trampled or not trampled (even when trampling effort was high). However, this could have been due to the fact that the level of trampling 58

62 (up to the equivalent of 200 people per week) was simply not high enough to cause any observable negative impacts. If such a study were conducted again, it might be worthwhile trying to increase the degree of trampling to levels similar to those actually found in Tortuguero (where frequently hundreds of tourists are on the nesting beach over the course of a week); this however, would significantly increase the effort involved in conducting the research. Another potential drawback to the protocol implemented in 2008 was that trampling ceased at day 50; it is likely that any reduction in hatching or emerging success would have been realized by trampling later in the incubation period, or when hatchlings had emerged from their shells but remained within the egg chamber. Therefore another recommendation for any repeat study would be to continue trampling until signs of hatching are observed, or until at least day 65 after oviposition. The results of these projects were presented at the International Sea Turtle Symposium in Australia in 2009, and the poster received considerable interest from symposium participants. Similar studies to evaluate potential negative impacts of tourism on turtles, eggs and hatchlings should definitely be incorporated into conservation projects as more turtle nesting beaches become tourism destinations. 5. References Carr, A., Carr, M.H., Meylan, A.B The ecology and migrations of sea turtles, 7. The west Caribbean green turtle colony. Bull. Amer. Mus. Nat. Hist. 162, de Haro, A., Troëng, S., Harrison, E., Silman, R., Rodríquez, D., Obando E Evaluation of new turtle-tour visitation system at Tortuguero, Costa Rica. Proceedings of the 26 th Annual Symposium on Sea Turtle Biology and Conservation, April 2006, Crete, Greece. de Haro, A Final report on the 2008 Turtle Spotter Program. Unpublished report presented to the Turtle Spotter Program Committee, Tortuguero, Costa Rica. 56pp. Debade, X., Nolasco, D., Harrison, E., Arana, J., Berrondo Ramos, L., Cortes Solano, J., Díaz Reviriego, I., Galean Gordon, L., Marrón Fiol, R., Martinetti, M., Neeman Horowitz, N., Gonzalez, R., Gamboa Ruiz, C and Vargas, E Report on the 2008 Leatherback Program at Tortuguero, Costa Rica. Unpublished reported presented to Caribbean Conservation Corporation and the Ministry of Environment, Energy and Telecommunications of Costa Rica. 46 pp. Troëng, S., Rankin, E Long-term conservation efforts contribute to positive green turtle Chelonia mydas nesting trend at Tortuguero, Costa Rica. Biol. Conserv. 121, Troëng, S., Dutton, P., Evans, D Migration of hawksbill turtles Eretmochelys imbricata from Tortuguero, Costa Rica. Ecography 28(3), Troëng, S., Solano, R., Díaz-Merry, A., Ordoñez, J., Taylor, J., Evans, D. R., Godfrey, D., Bagley, D., Ehrhart, L. & Eckert, S Report on long-term transmitter harness retention by a leatherback turtle. Marine Turtle Newsletter 111, 6-7. Wetherall, J.A Analysis of double-tagging experiments. Fish. Bull. 80,

63 6. Appendices Appendix 1. Nightly sea turtle encounters for the 2008 Green Turtle Program Date Leatherback Green Hawksbill New REM REN Total New REM REN Total New REM REN Total 12-Jun Jun Jun Jun Jun Jun Jun Jun Jun Jun Jun Jun Jun Jun Jun Jun Jun Jun Jun Jul Jul Jul Jul Jul Jul Jul Jul Jul Jul Jul Jul Jul Jul Jul Jul

64 Appendix 1. Continued Date Leatherback Green Hawksbill New REM REN Total New REM REN Total New REM REN Total 17-Jul Jul Jul Jul Jul Jul Jul Jul Jul Jul Jul Jul Jul Jul Jul Aug Aug Aug Aug Aug Aug Aug Aug Aug Aug Aug Aug Aug Aug Aug Aug Aug Aug Aug Aug Aug Aug Aug

65 Appendix 1. Continued Date Leatherback Green Hawksbill New REM REN Total New REM REN Total New REM REN Total 24-Aug Aug Aug Aug Aug Aug Aug Aug Sep Sep Sep Sep Sep Sep Sep Sep Sep Sep Sep Sep Sep Sep Sep Sep Sep Sep Sep Sep Sep Sep Sep Sep Sep Sep Sep Sep Sep Sep

66 Appendix 1. Continued Date Leatherback Green Hawksbill New REM REN Total New REM REN Total New REM REN Total 1-Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Oct Total Key to table New Turtles that had no tags on first encounter in 2008 REM Remigrant turtles that had tags from previous years/other projects on first encounter in 2008 REN Renester turtles that were encountered on more than one occasion during

67 Appendix 2. Photographs of the Junior Research Assistant Program 2008 Tortuguero High School students and FCs attend the 7 th Student Sea Turtle Symposium Junior Research Assistants help make information signs for tourists 64

68 Appendix 2 Continued Some of the Junior Research Assistants prepare for a night patrol with RAs Graduating Junior Research Assistants with the 2008 Green Turtle Program FCs and RAs 65

69 Appendix 3. Poster presented at the 2009 International Sea Turtle Symposium in Brisbane, Australia. 66