REPORT ON THE 2015 SEA TURTLE PROGRAM TORTUGUERO, COSTA RICA

Transcription

1 REPORT ON THE 2015 SEA TURTLE PROGRAM TORTUGUERO, COSTA RICA Submitted to Sea Turtle Conservancy and the Ministry of Environment and Energy of Costa Rica 8 February, 2016 by Raúl García Varela, Field Research Coordinator Guillermo López Torrents, Education and Outreach Coordinator Dr Emma Harrison, Scientific Director With assistance from Jose Luis Alvarez Morales, Research Assistant Tatiana Iretskaia, Research Assistant Guillermo Bas, Research Assistant Zara Jennings, Research Assistant Patrick Boyd, Research Assistant Katie Laybourn, Research Assistant Beatriz Brito Carrasco, Research Assistant Jasibe León Robles, Research Assistant Samuel Brown, Research Assistant Javier López Navas, Research Assistant Carlos Calagua Yon, Research Assistant Kyle Mealand, Research Assistant Dayana Calderón Molina, Research Assistant Céline Mollet Saint Benoît, Research Assistant Alix de Thoisy, Research Assistant Kiera O Hagan, Research Assistant Alberto García Baciero, Research Assistant Daniela Rojas-Cañizales, Research Assistant Jennifer Gooch, Research Assistant Hugo Sánchez Barón, Research Assistant Georgia Hallaman, Research Assistant Alma Vázquez Gómez, Research Assistant Erik Hansen, Research Assistant Emery Young, Research Assistant Jorge Ivan Ramos, Track Suveyor Address: Apartado Postal NW 13 th St. Suite B-11 San Pedro Gainesville, FL COSTA RICA USA Phone: INT INT Fax: INT INT emma@conserveturtles.org info@conservereturtles.org Webpage:

2 Table of Contents TABLE OF CONTENTS... I LIST OF TABLES... II LIST OF FIGURES... III ACKNOWLEDGMENTS... 4 EXECUTIVE SUMMARY INTRODUCTION METHODS Preparations Track Surveys Tagging of Nesting Sea Turtles Biometric Data Collection Determination of Nest Survivorship and Hatching Success Fibropapilloma Assessment Physical Data Collection Collection of Human Impact Data Satellite Tracking Project RESULTS Preparations Track Surveys Tagging of Nesting Sea Turtles Biometric Data Collection Determination of Nest Survivorship and Hatching Success Fibropapilloma Assessment Physical Data Collection Collection of Human Impact Data Satellite Tracking Project DISCUSSION Preparations Track Surveys Tagging of Nesting Sea Turtles Biometric Data Collection Determination of Nest Survivorship and Hatching Success Fibropapilloma Assessment Physical Data Collection Collection of Human Impact Data Satellite Tracking Project REFERENCES APPENDICES i

3 List of Tables Table 1. Incidence of poaching of nests, April May Table 2. Mean CCLmin and clutch size of leatherback turtles Table 3. Precision of carapace measurements for leatherbacks encountered more than once Table 4. Mean CCLmin of green turtles Table 5. Mean SCLmax of green turtles Table 6. Mean clutch size for green turtles Table 7. Precision of carapace measurements for green turtles Table 8. Mean carapace length and clutch size of hawksbill turtles Table 9. Precision of carapace measurements for hawksbill turtles Table 10. Fate, hatching and emerging success of marked hawksbill nests Table 11. Summary of data from nest excavations of marked leatherback nests during the 2015 Sea Turtle Program Table 12. Fate, hatching and emerging success of marked green turtle nests in Table 13. Summary of excavation data for green turtle nests marked in 2015 data combined from Tortuguero and Jalova Table 14. Summary of nests containing confiscated eggs Table 15. Summary of hawksbill excavations in Table 16. Summary of rainfall and air temperature data March to November, Table 17. Mean monthly sand temperature in Table 18. Number of visitors to the STC Visitors Center ii

4 List of Figures Figure 1. Temporal distribution of leatherback nesting at Tortuguero in 2015, as determined from weekly track surveys Figure 2. Leatherback nesting trend at Tortuguero, , as determined by weekly track surveys of the entire beach Figure 3. Temporal distribution of green turtle nesting at Tortuguero in 2015, as determined from weekly track surveys Figure 4. Green turtle nesting trend at Tortuguero, , as determined by weekly track surveys of the entire beach Figure 5. Spatial distribution of green turtle nesting at Tortuguero in 2015, as determined from weekly track surveys Figure 6. Temporal distribution of leatherback nests in 2015, as determined by three-day track surveys Figure 7. Spatial distribution of leatherback nesting in 2015; as determined by three-day track surveys Figure 8. Results of daily track surveys of the northern 5 2/8 miles of beach in Figure 9. Results of daily track surveys of the southern three miles of beach in Figure 10. Illegal take of nests and turtles in 2015, as determined from daily track surveys of the northern 5 2/8 miles of beach Figure 11. Summary of monthly light surveys conducted during the iii

5 Acknowledgments The 2015 Sea Turtle Program was conducted under a research permit from the Tortuguero Conservation Area (ACTo) of the Ministry of Environment and Energy (MINAE) of Costa Rica, detailed in resolution SINAC-ACTo-D-RES All the data presented here were collected by Field Research Coordinator (FRC) Raúl García Varela (Spain), Education and Outreach Coordinator (EOC) Guillermo López Torrents (Spain) and the dedicated team of Research Assistants (RAs): Jose Luis Alvarez Morales (Colombia), Guillermo Bas (Spain), Patrick Boyd (USA), Beatriz Brito Carrasco (Chile), Samuel Brown (UK), Carlos Calagua Yon (Peru), Dayana Calderón Molina (Costa Rica), Alix de Thoisy (France), Alberto García Baciero (Spain), Jennifer Gooch (USA), Georgia Hallaman (USA), Erik Hansen (USA), Tatiana Iretskaia (Russia), Zara Jennings (Canada), Katie Laybourn (USA), Jasibe León Robles (Mexico), Javier López Navas (Spain), Kyle Mealand (USA), Céline Mollet Saint Benoît (USA/France), Kiera O Hagan (Canada), Daniela Rojas-Cañizales (Venezuela), Hugo Sánchez Barón (Mexico), Alma Vázquez Gómez (Mexico) and Emery Young (USA). We also gratefully acknowledge the support staff and volunteers from Global Vision International who facilitated monitoring activities close to Jalova. The weekly track surveys of the entire beach were conducted by Jorge Ivan Ramos, whose considerable efforts we very much applaud. The dedication of all the John H. Phipps Biological Station staff was integral to the 2015 Sea Turtle Program. Station manager David Aparici Plaza provided logistical support; Diana Horgen administrated the Visitor Centre; boat captain Jorge Ivan Ramos safely transported researchers; Silvio López Hernández helped with station maintenance, Juanita Fernández made sure that everyone was well fed; Elisa Alvin was responsible for keeping the station clean and ensuring that everyone had clean clothes; and the station was kept secure by various security guards. Ms. Elena Vargas Ramírez and the park rangers of ACTo are due acknowledgement for their continuing efforts to protect sea turtles in Tortuguero National Park (TNP). We also acknowledge the continued support of the turtle spotters, tour guides and all of the Tortuguero community during the 2014 Sea Turtle Program. Our utmost gratitude is extended to National Director Roxana Silman and her assistant Maria Laura Castro in the Sea Turtle Conservancy (STC) office in San José, who provided logistical support throughout the Program. The help of STC staff in the Gainesville, Florida office is also recognized, for providing necessary equipment and help when requested. For financial assistance we would like to thank the Firedoll Foundation, the Leiter Foundation, the Marisla Foundation, the Treadright Foundation and all the 2014 Eco-Volunteers. 4

6 Executive Summary Monitoring and Research Activities Conducted 1 During 2015, a total of 44 track surveys were conducted along the entire 18 miles of beach between Tortuguero river mouth and Jalova lagoon. 2 The first leatherback nest was recorded on 28 February. Green turtle nesting was observed regularly between June and November; with the first nest recorded on 28 February. 3 Leatherback nesting was very low, with nesting only observed on six weekly track surveys. 4 An estimated 154 leatherback nests were laid during Peak green turtle nesting was recorded on 15 September; 1,757 green turtle nests were counted in a single night. 6 An estimated 74,006 green turtle nests were laid during This equates to a population of 12,334 26,431 nesting females. 7 Only one hawksbill nest was observed during weekly track surveys. 8 The Field Research Coordinator (FRC) and Research Assistants (RAs) conducted 19 additional track surveys from the Tortuguero rivermouth to the Jalova lagoon between 4 April and 28 May, A total of 181 leatherback, 76 green turtle and 11 hawksbill nests were registered during the threeday track surveys. 10 During daily track surveys conducted from 7 June 1 November a total of 18,864 green turtle nests and 25,917 false crawls were recorded from the Tortuguero river mouth (mile 2/8) and mile 5. Surveys from mile 15 to the Jalova lagoon registered 5,700 nests and 7,687 false crawls. 11 A total of 123 nests were recorded as poached during monitoring activities of the 2015 Sea Turtle Program; 115 green turtle, four leatherback and four hawksbill. 12 Sixty-two turtles were poached from the beach in 2015; 61 green turtles and one hawksbill. 13 Jaguars killed a minimum of 93 turtles during 2015; 90 green turtles, one leatherback and two hawksbills. 14 Two green turtles were found alive, following poaching attempts; they were both released successfully. 15 2,563.5 team hours of night patrols were conducted from 1 April 29 October; 1,984.0 hours in Tortuguero and hours in Jalova. 16 A total of 1,823 encounters with nesting females were recorded in 2015; 68 leathebacks, 1,740 green turtles, 14 hawksbill and one loggerhead. 17 A total of 52 individual leatherbacks were encountered; 15 newly tagged females and 37 with tags from previous years or other nesting beaches. 18 Of the previously tagged leatherbacks, only one (2.7%) was originally tagged in Tortuguero; the 5

7 others were from other beaches such as Mondonguillo, Gandoca, Panama, Parismina, Caño Palma, Pacuare and Mexico. 19 The oldest leatherback was originally tagged at Tortuguero in 1999, 16 years previously. 20 The majority of leatherbacks nested in the open zone (55.9%); there were 19.1% in the border zone and 25.0% did not nest successfully when encountered. 21 A total of 1,491 individual green turtles were encountered; 1,067 newly tagged females and 425 with tags. 22 Of the previously tagged green turtles, 156 were originally tagged in Tortuguero more than 10 years ago and eight more than 20 years ago. The oldest green turtle was tagged in 1984, 31 years ago of the newly tagged green turtles had evidence of old tag holes or notches in at least one front flipper when first encountered. 24 The majority of green turtles nested in the border zone (64.5%); 24.7% in the open zone, 9.0% in the vegetation zone and 1.8% were encountered during a false crawl emergence. 25 Mean CCLmin of leatherback turtles was 151.2cm and mean clutch size was 74.6 yolked and 25.1 yolkless eggs. 26 Carapace length of green turtles ranged from cm (CCLmin) and cm (SCLmax). 27 Mean clutch size for green turtle nests was eggs. 28 Carapace length for hawksbill turtles ranged from cm (CCLmin) and cm (SCLmax). 29 Mean clutch size of hawksbill nests was eggs. 30 Precision of CCLmin measurements was the same for all species (0.5cm) and for SCLmax it was 0.4cm (green turtle) and 0.7cm (hawksbill). 31 Thirty-one leatherback nests were marked and monitored; 11 in Tortuguero and 20 in Jalova. 32 Overall mean hatching success for leatherback nests was estimated at just 8.87% and emerging success was 8.2%. 33 Incubation period of leatherback nests ranged from days, with a mean of 68 days. 34 A total of 202 green turtle nests were marked; 147 in Tortuguero and 55 in Jalova. 35 Mean green turtle hatching success was estimated at 52.2% and emerging success was 49.2%. 36 Mean incubation period of green turtle nests was 60 days in Tortuguero and 65 days in Jalova. 37 A total of two albino embryos and two deformed embryos were observed in unhatched eggs, accounting for 0.034% of green turtle eggs. 38 Three nests were marked containing confiscated eggs; only one was successful, with a hatching and emerging success of 78.0% and 77.2%, respectively. 6

8 39 Nine hawksbill nests were monitored; mean hatching and emerging success was 41.4% and 37.6%, respectively. 40 None of the 181 green turtles checked for fibropapiloma (FP) showed signs of the disease. FP tumors were found on six turtles during the routine body check; other types of tumor were seen on 10 other turtles. 41 August was the month with the most rainfall (859.9mm) and October was the driest month (209.0mm). 42 Air temperature ranged from ºC in It was only possible to measure sand temperature in the vegetation zone; it ranged from ºC. 44 Visitation to the STC Visitor Center increased by more than 2,600 in A total of 18,304 visitors were registered; an average of 50 people per day. 45 There was a decrease in the number of artificial lights visible on the beach from June, probably the result of the changes to the orientation of several light fittings made by ICE personnel. 46 There were no incidents of hatchling disorientation observed in Two green turtles and one hawksbill were tracked using satellite telemetry. The hawksbill went to Nicaragua and the greens travelled to Mexico and Colombia; this was the first time that a turtle was tracked migrating south from Tortuguero Conculsions 1 There were many problems with beach erosion during the 2015 leatherback nesting season and this was one of the reasons for the very low number of nests recorded, continuing the worrying negative nesting trend observed since The green turtle nesting season was a little delayed in 2015, possibly due to the very high tides during many months. However, at the end of the season, nesting levels were not too low. 3 The level of illegal poaching of nests and turtles was similar to that reported in other years, with the same spatial distribution pattern as that seen previously, with incidents reported close to the river mouth and the limit of TNP 4 Hatching and emerging success of both leatherback and green turtle nests was much lower in 2015 than in 2014; resulting from the high number of nests lost to erosion throughout the year. 5 It was very exciting to track a green turtle migrating south, after many years of the satellite tracking study, rather than following the more habitual migration route north to Nicaragua. Recommendations 1 Delays during the application process for the research permit affected the start of monitoring activities for the 2015 Sea Turtle Program by several weeks. To avoid similar issues in the future, it would be a good idea to establish an official agreement between STC and SINAC to facilitate these procedures for both parties and also improve the level of collaboration between the two entities. 2 All of the monitoring activities should continue in the future, as they provide valuable data to 7

9 increase our knowledge of sea turtle populations at Tortuguero, which can help TNP administrators make decisions relating to their management and that of critical habitats within the protected area. 3 To have a more complete understanding of leatherback nesting and threats to nests, STC should initiate night patrols in the section of beach between Jalova and Parismina, to conduct a pilot study to investigate if relocation or camouflaging of leatherback nests would be appropriate strategies to reduce poaching of nests of this endangered species 4 Marking and monitoring of turtle nests should be continued to determine the threats to their survival and hatching and emerging success. 5 It is vital for the survival of eggs confiscated by the relevant authorities that there is proper collaboration with STC, to ensure the proper handling of the eggs and their relocation, as well as their subsequent monitoring during the incubation period. 6 Collection of physical data should continue, to provide a baseline of environmental parameters for Tortuguero beach. 7 An Education and Outreach Coordinator should be contracted for future programs to implement an education program in the community, and to act as the liaison between STC, the National Park and the people of Tortuguero. This should be an integral part of the turtle conservation program in Tortuguero. For the future survival of turtles it is vital to involve local residents, and build a conservation ethic, particularly in the younger generation, to protect their natural resources. The Junior Research Assistant program is key to this initiative, as it provides students with first-hand experience participating in the monitoring and research activities conducted by STC. 8 STC should provide regular updates of the results of the program to TNP staff and tour guides throughout the season, including interesting turtle encounters and nesting distribution. 9 Regular reports should be provided to TNP staff regarding observations of illegal take of turtles and nests, on the nesting beach and other areas. 10 TNP, with support from STC, needs to conduct a carrying capacity study to determine maximum limits relating to sea turtle tours on the beach at night; to include the total number of people permitted per night or per section of beach, the total number of people permitted to observe each turtle, and establish a minimum distance between turtles being observed to prevent crowding. 11 STC, with TNP and the tour guides, need to ensure that the entrances to the beach used during the Turtle Spotter Program are blocked sufficiently to avoid turtles gaining access to the trail behind the beach or the airport landing strip, while allowing access to people. 12 STC needs to continue the collaboration with the Costa Rican Electricity Institute (ICE) to reduce the number of artificial lights visible on the nesting beach, especially the public street lights that are the main problem. 13 STC should continue the Red Lights// nn - project, swapping the bulbs in house and hotel lights in the village for more turtle friendly alternatives, and at that same time initiate a revegetation program to plant native species between the beach and village buildings, to help reduce the problem of artificial light that is negatively impacting sea turtle hatchlings. 14 The satellite tracking project should continue in future years; it is a great way to find out the migration routes of turtles nesting at Tortuguero, to determine what possible threats turtles may face during migration and also know where their feeding areas are located. 8

10 1. Introduction Dr. Archie Carr began studies of green turtles (Chelonia mydas) in Tortuguero in 1954 (Carr et al. 1978). STC initiated the annual leatherback (Dermochelys coriacea) program in 1995 (Campbell et al. 1996). The research programs are implemented to fulfill STC s scientific mission in Tortuguero: 9 STC 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 objectives of this report are to summarize and discuss the results of the 2014 Sea Turtle Program, evaluate the achievements and deficiencies of the program and provide recommendations for future conservation efforts and sea turtle research activities in Tortuguero. 2. Methods The monitoring protocol used during the 2015 Sea Turtle Program is detailed below; this protocol was submitted as part of the research permit application to ACTo MINAE in December, Preparations Prior to the start of monitoring activities at Tortuguero in 2015, STC signed an agreement with Global Vision International (GVI), a volunteer organization that has a project in Tortuguero National Park. The agreement detailed how GVI staff and volunteers would be trained by STC and assist in monitoring activities close to the Jalova lagoon. At the start of the 2015 Sea Turtle Program the Research Assistants (RAs) completed an extensive orientation and training program; they received lectures about sea turtle biology and conservation, the Sea Turtle Program monitoring protocol was explained in detail and they conducted training patrols at night. They also 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. GVI staff and volunteers replaced and repainted mile markers from mile Track Surveys Weekly track surveys Track surveys were carried out approximately weekly throughout the year. The track surveyor conducted surveys between the Tortuguero river mouth (mile -3/8) and Jalova lagoon (mile 18). The surveys commenced at dawn at Tortuguero village, and finished at Jalova lagoon. The section between Tortuguero river mouth and the village was surveyed 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

11 2.2.2 Three-day track surveys Track surveys were conducted by the FRC and RAs between the Tortuguero river mouth and the Jalova lagoon every three days from March May, following the completion of the RA orientation and training period. The beach was divided into three sections: Tortuguero river mouth - STC station (mile 2 5/8); STC station - Juana López trail (mile 15) and Juana López trail - Jalova lagoon (mile 18). All tracks since the previous survey were recorded, to get a total count of all nesting activity throughout the season. Once a track had been registered two lines were drawn through it, and sticks were placed in a cross formation over the nest, to ensure that it was not counted on future surveys Daily track surveys Daily track surveys along the northern 5 2/8 miles of beach (from the Tortuguero river mouth to the mile 5 marker) and the southern three miles at Jalova (from Jalova lagoon to mile 15) were conducted 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 Once a nest had been recorded two lines were drawn through the track to ensure that it was not counted on future surveys Illegal take of nests and turtles During track surveys, researchers also recorded the level of illegal take of nests and nesting turtles, and nest predation. 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 broken 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). Nests were considered predated if there were signs of animal disturbance, including tracks and evidence of digging. For each nest/turtle the following information was recorded: Species Mile If the nest and/or turtle was poached by humans If the nest/turtle was predated Identify the predator if possible Dead turtles Any dead turtles encountered during track surveys or other monitoring activities were examined and an attempt was made to determine the cause of death. Dead turtles were considered predated by jaguars (Panthera onca) when they were surrounded by jaguar tracks, the carcass showed characteristic jaguar injuries, such as extensive bite marks to the neck, and/or there was evidence that the body had been dragged off the beach into the vegetation. 10

12 For each turtle the following information was recorded: Species Mile Sex if possible to determine If the turtle was killed by a jaguar Cause of death if possible to determine Presence of flipper tags numbers recorded if present Other pertinent observations Turtles encountered alive and flipped over If turtles were encountered alive but flipped over they were carefully examined for injuries and tags and then released back to the sea. For each turtle the following information was recorded: Species Mile Time of encounter Tag number/s if present Other pertinent observations 2.3 Tagging of Nesting Sea Turtles Tagging teams patrolled the beach every night from March - 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. Trained GVI staff and volunteers conducted additional patrols in the southernmost three miles of beach, between mile 15 and the Jalova lagoon. Female turtles encountered during the patrol were tagged after finishing oviposition or when returning to the sea. Leatherbacks were tagged in the rear flippers; hard-shelled species 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 Name of the person applying the tags 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 vegetation for some part of the day Vegetation dense vegetation completely shading the nest throughout the day Leatherback turtles Leatherback turtles were tagged in the rear flippers using Monel #49 tags. 11

13 2.3.2 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 Hawksbill turtles Hawksbill (Eretmochelys imbricata) turtles were tagged with Inconel #681 tags. 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. 2.4 Biometric Data Collection Leatherback turtles If the turtle was encountered before the start of oviposition, the eggs were counted as they were laid into the egg chamber. They were counted by a person wearing a plastic glove to avoid contamination of the nest. Yolked and yolkless eggs (those that have just the albumen surrounded by a shell, with no yolk present) were counted separately. Curved Carapace Length minimum (CCLmin) was recorded for each turtle. It was measured, using a fiberglass measuring tape, from where the skin meets the carapace by the notch of the neck to the posterior end of the caudal projection, to the right of the central ridge. Two people were required to take the measurements. Each turtle was measured three times to determine an average CCLmin. Measurements were taken to the nearest millimeter. The caudal projection was classified as complete if no irregularities occurred and incomplete if it was irregular or part of it was missing that would affect the carapace measurement Green turtles An attempt was made to count one clutch of eggs per night in each of the two northern beach sections (Boca and Park) and at least one clutch per night in the southern beach section (Jalova) during peak green turtle nesting season (June September). Eggs counts were conducted as described above. All egg counts were conducted after midnight, when there were no tour groups present on the beach. CCLmin was measured, using a fiberglass tape measure, from where the skin meets the carapace by the nuchal notch to the posterior notch between the supracaudals, along the midline. 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. All measurements were taken to the nearest millimeter. 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 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 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 12

14 the precision to be calculated. Whenever possible the clutch was counted, if the hawksbill had not already started to lay eggs when encountered. 2.5 Determination of Nest Survivorship and Hatching Success A sample of leatherback, green turtle and hawksbill nests were marked for inclusion in the study of nest survivorship and hatching success. Nests were only marked if the turtle was encountered while the egg chamber was still open (prior to covering) and the turtle was located between Tortuguero river mouth (mile -3/8) and the mile 5 marker at the northern end of the beach, or between mile 15 and the Jalova lagoon at the southern end of the beach. The location of the egg chamber was 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 center of the egg chamber to each of these tapes was measured to the nearest centimeter, so that the location of the nest could be determined at the time of excavation using triangulation. Use of a third flagging tape ensured that the nest could still be located even if one of the tapes was lost as a result of camouflaging turtles, insects or persons removing the tapes intentionally. The distance to the most recent high tide line was also recorded at the time of oviposition. 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. In addition, the morning after a nest was marked the measurements were checked to ensure that they crossed; any discrepancies were re-checked by the researchers responsible for marking the nest the previous night. In this way, erroneous measurements, or errors during the recording of data in the field books could be identified and corrected immediately. All of the marked nests were inspected daily. 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. Also, it was recorded if the nest had been washed over or inundated by the tide during the previous 24 hours. If evidence of hatching was observed, the date was noted and the nest was excavated two days later. If no depression or hatchling tracks were recorded, the nest was excavated after 65 days (75 days for any leatherback nests). After 75 days (leatherbacks) or 65 days (green or hawksbill turtles), or sooner if signs of emergence had been recorded, the nest was excavated, once the distances from the marker tapes had been remeasured to confirm that it was the original nest. Nests that had no obvious depressions were located by carefully probing for soft sand using a wooden stick (only after 75/65 days, when it was presumed that hatching and emergence had occurred), and this technique greatly aided in locating several of the marked nests for which hatching had not been recorded. The excavation was discontinued if the researcher encountered a large number of hatchlings in the nest; in such cases the hatchlings were reburied 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 13

15 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 additional attempt was made the following morning by a different research team. If after two attempts the nest could not be found, researchers tried to determine the fate of the nest. Nests were considered poached if an empty egg chamber was encountered. Nests were assumed dug-up by another turtle if broken eggshells and/or the nest code tape from within the egg chamber, 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. 2.6 Fibropapilloma Assessment For a minimum sample of 100 green turtles, those for which clutches were counted, an examination for the presence of fibropapilloma tumors was also conducted. All soft body parts, including the cloacal region, were inspected, using a flashlight with a red filter. The following data were recorded for each assessment: The presence or absence of fibropapilloma tumors Location of fibropapilloma tumors observed Size of any tumors detected The name of the person examining the turtle Any evidence of fibropapilloma tumors on turtles during the routine body check was also recorded. 2.7 Physical Data Collection Throughout the 2015 Sea Turtle Program several environmental variables were monitored on a daily basis at the John H. Phipps Biological Station in Tortuguero. 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 14

16 hours, and the current temperature were noted. Sand temperature was measured using dataloggers buried at 30, 50 and 70cm depth in the open, border and vegetation zones of the beach in front of the STC station. The data loggers were set to take a temperature reading every hour. The data were downloaded at the end of the 2012 Green Turtle Program. 2.8 Collection of Human Impact Data Visitors to Tortuguero The number of visitors paying to enter the STC Visitor Center was recorded each day during 2015 by the Visitor Center Administrator 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 Mile section Number of lights visible from the beach Light source (if possible to determine) To avoid duplicate recording of the same light source in multiple 1/8 mile sections of beach, only those lights that could be seen while viewed perpendicular from the beach were recorded in each 1/8 mile Hatchling disorientation Any evidence of hatchling disorientation was recorded, for marked or unmarked nests. Where possible the light source causing the disorientation was noted, in addition to the number of disorientated hatchlings encountered (dead or alive) and the number of hatchlings that reached the sea successfully. 2.9 Satellite Tracking Project Continuing the satellite tracking project that has been conducted by STC within the Caribbean region since 2001, in 2015 three satellite transmitters were available for attachment to a green or hawksbill turtle. These turtles were included in the 2015 Tour de Turtles; an on-line education event run by STC to raise awareness about sea turtles, their migration behavior and threats that they face. The transmitters were attached during the middle of the nesting season (July); the data would provide information on inter-nesting behavior between nesting emergences and also post-nesting migrations to feeding grounds away from Costa Rica. The turtles were selected by researchers depending on their size, physical characteristics of the carapace (to aid attachment by not having any deformities or irregularities in the scutes) and distance from the field station (to facilitate their relocation to the station where they were retained overnight). The transmitter was attached at 6.00am the following morning, using the protocol detailed in Coyne et al.(2008). Visitors from the lodges and cabinas, and members of the community were invited to 15

17 observe the attachment procedure and subsequent release of the turtle. STC researchers were available to answer any questions about sea turtles, satellite telemetry or the work of STC. Data from the transmitters were used to produce migration maps which were regularly updated on the Tour de Turtles website ( 3. Results 3.1 Preparations The agreement between STC and GVI facilitated collaboration between the two organizations; GVI staff and volunteers assisted in the collection of data for the 2015 Sea Turtle Program. The additional personnel allowed beach patrols to be conducted in the section of beach close to Jalova for the second consecutive green turtle nesting season. The first training and orientation of RAs was conducted from March, 2015 by the FRC, with support from the Scientific Director (SC). In addition to lectures about sea turtle biology, nesting behavior and the history and structure of STC the RAs also received practical training in flipper tagging, nest marking and other data collection procedures. Due to the delay in the processing of the research permit it was not possible to conduct supervised patrols with the RAs until 1 April, when the permit arrived in Tortuguero. Other RA training sessions were also conducted in June and August. As in previous years, many of the mile markers on the beach needing replacing at the start of the 2015 Sea Turtle Program; the FRC and RAs were assisted in this task by GVI staff and volunteers, who checked the markers between miles The very high tides during the first few months of the year meant that it was not possible to mark the entire beach in March, therefore the mile markers were replaced/painted throughout the season once the beach had recovered sufficiently. The photos in Appendix 1 show the level of beach erosion during the first few months of the 2015 turtle nesting season. 3.2 Track Surveys Weekly track surveys A total of 44 weekly track surveys were conducted from 3 January to 26 December, The track surveyor injured his knee in April, which meant that there were several weeks when it was not possible to conduct the surveys. The first turtle tracks were registered in February and the last were seen in November Leatherback turtles The first leatherback nest was recorded on 28 February, and the last were observed on 30 May. Figure 1 shows the results of the weekly surveys, each bar represents the number of nests and false crawls recorded during each survey. There was very limited leatherback nesting in 2015 (tracks of this species were only registered during six track surveys during the entire season), probably because there was very little beach available to the females (See Figure 1). Peak nesting occurred on 30 May when four leatherback nests were recorded from the previous night. Using the methodology described in Troëng et al. (2004), extrapolation from the weekly track surveys suggests that 154 leatherback nests were laid between the Tortuguero river mouth and the Jalova lagoon during the 2015 nesting season. 16

18 The leatherback nesting trend at Tortuguero since 1995 can be seen in Figure 2. There was a very slight increase in the number of leatherback nests laid in 2015, though the overall trend since 1995 continues to show a decline. Using the estimations calculated from the weekly track survey data, in the last five years there has been an average of 181 leatherback nests laid each season Green turtles The first green turtle nest was registered on 28 February, 2015, and nesting was observed regularly from July October (See Figure 3). The season was delayed by almost one month; the level of nesting in June was very low, and only started to increase significantly in July. There were two nesting peaks, one in the middle of August and another in the middle of September. The night with the highest level of nesting was 15 August, when 1,757 nests were recorded (See Figure 3). Using the methodology of Troëng & Rankin (2005), it was estimated that 74,006 green turtle nests were laid along the entire 18 miles of beach during the 2015 nesting season (See Figure 4). This equates to a population of between 12,334 26,431 nesting females. The pattern of green turtle nesting was different to that typically observed. As in previous years nesting increased within TNP (after mile 3) and there was very obvious peak at mile 11 (See Figure 5); 14.5% of all nests counted were in this mile. Nests laid between the Tortuguero river mouth and the mile 5 marker, and between miles in Jalova, where nightly beach patrols were regularly conducted, accounted for 29.6% of all nests laid on the entire beach Hawksbill turtles Only one hawksbill nest was registered during the weekly surveys in 2015, on 22 May Three-day track surveys The FRC and RAs conducted 19 track surveys of the 18 miles of nesting beach from the Tortuguero river mouth to the Jalova lagoon between 4 April and 28 May, Due to the very high tides that almost reached the vegetation behind the beach, it was very complicated to conduct the three-day track surveys; on various occasions it was not possible to walk along the entire beach because of the waves and fallen trees. For this reason, the data presented should be viewed as the minimum values for the season. A total of 181 leatherback, 763 green turtle and 11 hawksbill nests were registered, in addition to 133 leatherback, 71 green turtle and two hawksbill false crawls. Nesting levels were very low, with the majority of nests laid in April; temporal distribution of leatherback nesting is shown in Figure 6. The high number of nests recorded on 4 April was due to the fact that during this first survey all tracks were counted, since the beginning of the season. Two peaks were observed, on 7 April and 1 May, when 21 nests were laid during the three previous nights. The spatial distribution of leatherback nesting during 2015 is shown in Figure 7; the majority of nesting was observed at the southern end of the beach, between miles

19 Figure 1. Temporal distribution of leatherback nesting at Tortuguero in 2015, as determined from weekly track surveys 18

20 19 Figure 2. Leatherback nesting trend at Tortuguero, , as determined by weekly track surveys of the entire beach

21 Figure 3. Temporal distribution of green turtle nesting at Tortuguero in 2015, as determined from weekly track surveys 20

22 21 Figure 4. Green turtle nesting trend at Tortuguero, , as determined by weekly track surveys of the entire beach

23 Figure 5. Spatial distribution of green turtle nesting at Tortuguero in 2015, as determined from weekly track surveys 22

24 23 Figure 6. Temporal distribution of leatherback nests in 2015, as determined by three-day track surveys

25 Figure 7. Spatial distribution of leatherback nesting in 2015; as determined by three-day track surveys 24

26 3.2.3 Daily track surveys Daily track surveys were conducted by the FRC and RAs between 7 June and 1 November, except for 8 and 14 June. A total of 18,864 green turtle nests and 25,917 green turtle false crawls were recorded between the Tortuguero river mouth and the mile 5 marker (See Figure 8a and 8b); successful nesting was observed in 42.1% of green turtle emergences. Figure 8a shows the spatial distribution of green turtle nests and false crawls for the northern 5 2/8 miles of beach. Nesting density per 1/8 mile was greater within TNP, past mile 3 3/8 (See Figure 8a). In total, 48.8% of all nests were laid between mile 3 3/8 and mile 5. The 1/8 mile with highest nesting was mile 4 6/8, with 1,008 nests. There were various nests with very little nesting (eg. miles 1 1 3/8 and between 2 1/8 3 2/8), which was due to the limited amount of beach available as a result of high tides and fallen trees in these sectors. The temporal distribution of green turtle nesting is shown in Figure 8b. As in 2014, nesting season was very delayed, with few nests laid in June. Peak nesting was recorded on 10 September, when 590 green turtle nests were recorded from the previous night. There were only two nights during the entire season when more than 400 nests were recorded. It is interesting to compare Figures 3 and 8b, which show the temporal distribution of weekly and daily track surveys; the nesting pattern is quite different in the two figures, with the peak of nesting in September shown very clearly in the data from the daily track surveys. The last leatherback nest was reported on 7 June, and the last false crawl was on 22 July. Hawksbill nesting activity was observed from June September. A total of 20 nests and 69 false crawls were recorded; the majority of the nests (n = 7) were deposited in September. One loggerhead (Caretta caretta) nest was seen on 5 July. Daily track surveys were conducted by the GVI staff and volunteers between 8 June and 29 October, except 5 and 17 September. A total of 5,700 green turtle nests and 7,687 green turtle false crawls were recorded between mile 15 and the Jalova lagoon (See Figure 9a and 9b); successful nesting was observed in 42.6% of green turtle emergences at the southern end of the beach. The peak of nesting was one month before the peak observed at the northern end of the beach; it was seen on 11 August, when 241 green turtle nests were counted from the previous night (See Figure 9b). In addition, 14 leatherback nests and one false crawl were recorded during daily track surveys close to Jalova; the last nest was on 28 June. Hawksbill nesting was observed from June September; a total of seven nests and 20 false crawls were registered. 25

27 Figure 8. Results of daily track surveys of the northern 5 2/8 miles of beach in 2015 a) Spatial distribution b) Temporal distribution 26

28 Figure 9. Results of daily track surveys of the southern three miles of beach in 2015 a) Spatial distribution b) Temporal distribution 27

29 3.2.4 Illegal take and nest predation Weekly track surveys The number of green turtle nests reported as poached during the weekly track surveys was low in 2015; a total of 27 nests were poached from May October. Also, there was a slight increase in the number of green turtles that were taken; between July October there was evidence that 38 females were flipped over and dragged off the beach. Of these, 21 were taken on a single night (5 September). Unfortunately, the majority of nests and turtles were poached from within TNP, between miles 8 4/8 12, but there were also various nests poached close to the Tortuguero river mouth, between miles -2/8 and mile 0. One leatherback and one hawksbill nest were also poached, but no hawksbill females were taken Three-day track surveys During the leatherback nesting season a total of four nests were reported as poached; three leatherback and one hawksbill (See Table 1); the nests were taken from within TNP and also the public sector of the beach. No green turtle nests were poached Daily track surveys Table 1. Incidence of poaching of nests, April May 2015 Date Leatherback Hawksbill # nests Mile # nests Mile 4-Apr 1 7 4/ Apr May May /8 Total 3 1 During the daily track surveys researchers also noted the level of illegal take of both eggs and female turtles (See Figure 10a and 10b). In total, 90 fresh nests were taken from June October; 88 green turtle nests (0.5% of the total) and two hawksbills. A further 15 old (more than one day) green turtle nests were also taken. Twenty-three green turtles and one hawksbill were taken from the nesting beach. From Figure 10a it can be seen that nest poaching occurred along the entire five miles of beach from the river mouth to mile 5, but there was a peak just on the limit of TNP at mile 3 3/8. The take of turtles was registered from the river mouth to mile 4 1/8, but it was concentrated at the northern end of the beach, between mile -1/8 and 3/8 (See Figure 10a). Poaching, of either nests or turtles, was observed during 59 of 147 (40.1%) track surveys between June and October (See Figure 10b). The worst night was 8 August, when 13 green turtle nests were taken (See Figure 10b). Poaching of nests and turtles was observed throughout the nesting season, although more nests were taken at the start of the season, and more turtles towards the end (See Figure 10b). 28

30 Figure 10. Illegal take of nests and turtles in 2015, as determined from daily track surveys of the northern 5 2/8 miles of beach a) Spatial distribution b) Temporal distribution 29

31 The level of predation of nests by dogs was low in 2015; 13 green turtle nests (0.07%) were predated between June October in the northern five miles of beach, close to Tortuguero village. Five green turtle nests were reported as poached during the surveys of the three miles of beach close to Jalova from June October; four were taken on one night on 24 July, between miles /8. The same night one green turtle was taken from mile 15 5/8. No green turtle nests were reported as predated by dogs close to the Jalova lagoon Dead turtles A total of 93 green turtles and one hawksbill were reported killed by jaguars during the 2015 Sea Turtle Program; 90 green turtles, one leatherback and two hawksbills (See Appendix 2); the majority of these turtles were found during the weekly track surveys of the 18 miles of beach. All of the jaguar predation occurred within TNP, between miles 4 2/8 and 17 4/8. There were several surveys when more than five turtles (up to seven) were found dead in a single night. Only turtles from the previous night were counted during these surveys, so this value should be considered as a minimum number of turtles killed by jaguars Turtles found flipped over and alive Two green turtles were found flipped over and alive during the 2015 Sea Turtle Program; one on 2 August (close to the river mouth) and one on 11 August (mile 2 1/8). The two individuals were helped to the beach and returned to the sea; neither was encountered stranded afterwards, and so it was assumed that they survived. In addition, there were five occasions when turtles were found alive crawling on the trail behind the beach or on the landing strip at the airport (See Appendix 3). All of these turtles were helped back to the beach and returned to the sea. 3.3 Tagging of Nesting Sea Turtles Tags used during the 2015 Sea Turtle Program were National Band & Tag Company Monel #49 tags VC4451-VC4468, VC4470-VC4473, VC4477, VC4480-VC4482, VC4501-VC4514 and VC4526-VC4549 and Inconel #681 tags , , and Due to the delay in receiving the research permit, no night patrols were conducted in March, they started in April. Nightly patrols were conducted from 1 April 29 October, 2015 (except 6, 10 and 14 June); up to five patrols were realized each night in the different sections of the beach. A total of 2,563.5 team patrol hours were logged; 1,984.0 in Tortuguero and by GVI between miles in Jalova Leatherback turtles A total of 68 leatherback encounters were registered, which corresponded to 52 different individuals; 15 newly tagged females (28.9%) and 37 (71.1%) with tags. There were 16 turtles observed more than one during the season (See Appendix 4). Of the turtles with tags (n = 37), only one (2.7%) had originally been tagged at Tortuguero in The others were tagged by researchers at Caño Palma (n = 2), Parismina (n = 5), Pacuare (n = 19), Mondonguillo (n = 2) and Gandoca (n = 1). There were three turtles that were possibly 30

32 tagged at Moín. Three turtles were encountered that were tagged in Panama and another three individuals had tags that were used at projects in Mexico. The SD contacted researchers there, but has not received any information about where they were originally tagged. Evidence of old tags was found in five of the 15 (33.3%) newly tagged leatherbacks checked for tags when encountered for the first time. The majority of leatherbacks nested in the open zone (55.9%, n = 38); 19.1% nested in the border zone (n = 13) and 25.0% did not nest successfully (n = 17) Green turtles A total of 1,740 green turtle encounters were recorded in 2015; 1,539 in Tortuguero and 201 in Jalova (See Appendix 4). These encounters included 1,491 individual females; 1,067 (71.5%) initially observed without tags and 425 (28.5%) who had tags. In addition, there were 248 encounters with turtles observed more than once during the 2015 nesting season. One green turtle male was also encountered and tagged. There were 21 green turtles tagged at other nesting beach projects in Costa Rica; 19 were tagged by researchers at Caño Palma, one at Mondonguillo and one at Pacuare Nature Reserve. The SD is awaiting confirmation of original tagging dates from researchers working at those beaches. In addition there was one female encountered with tags from another country; AM704. This turtle was originally tagged in Mexico, but there is no information about which year she was tagged in. She also nested at Tortuguero in The other females that had tags were all originally tagged in Tortuguero. There were 156 individuals that had been tagged more than 10 years previously; of these, eight were tagged more than 20 years ago. The longest recapture in 2015 was ID #28301; she was originally tagged in 1984, and was seen in nine nesting season in the intervening 31 years; 1988, 1991, 1995, 1998, 2001, 2004, 2007, 2010 and 2012). Of 1,043 newly tagged green turtles checked for the evidence of old tag holes or notches when encountered for the first time during the 2015 Sea Turtle Program, 205 (19.6%) had evidence in at least one flipper. Beach zone was recorded for 1,742 green turtles encounters; 24.7% (n = 431) of those females nested in the open zone, 64.5% (n = 1,123) were located in the border zone, 9.0% (n = 157) in the vegetation zone and 1.8% were encountered while making a false crawl (n = 31) Hawksbill turtles Fourteen hawksbill encounters were logged during the 2015 Green Turtle Program (See Appendix 4); nine newly tagged and five previously tagged individuals. Two of the previously tagged females were tagged in Tortuguero, in 2011 and 2013, one turtle was tagged at Caño Palma in 2013 and one at Parismina in The SD is in contact with the Archie Carr Center for Sea Turtle Research in Florida to find out where and when one other turtle was tagged. Only one (11.1%) of the newly tagged females had evidence of old tag holes or notches. Eight of the 15 hawksbill nests (53.3%) were laid in the border zone, six (40.0%) in the vegetation zone and one (6.7%) female did not lay successfully. 31

33 3.3.4 Loggerhead turtles One newly tagged loggerhead was encountered on 5 July in Tortuguero; there was no evidence of previous tags and the nest was laid in the open zone. 3.4 Biometric Data Collection Leatherback turtles Table 2 summarizes the biometric data collected from leatherback females. CCLmin measurements were taken for 48 of 51 females encountered. Only six turtles (three newly tagged and three with tags) had a caudal projection registered as incomplete, so measurements from all turtles were analyzed together. Twenty- three nests were counted; one turtle only laid two eggs, so this nest was excluded from the analysis. Two analyses were conducted to see if there was a difference in CCLmin and clutch size between newly tagged and previously tagged females; resulted indicated that there were no significant differences (CCLmin T-test: t = 0.153, p = 0.879; Clutch size T-test: t = 2.408, p = 0.24); therefore data from all turtles were analyzed together. To ensure independence of the data, only the first CCLmin measurement taken for each individual was included in the analysis. Mean CCLmin was 151.2cm and mean clutch size was 74.6 yolked and 25.1 yolkless eggs. Table 2. Mean CCLmin and clutch size of leatherback turtles Variable n x ± S.D Range CCLmin / cm ± Yolked eggs ± Yolkless eggs ± The mean precision of CCLmin measurements for leatherback turtles was 0.5cm (range of 0 1.1cm). The precision of measurements encountered more than once are shown in Table 3. Precision ranged from cm. Table 3. Precision of carapace measurements for leatherbacks encountered more than once Green turtles No. of encounters n x precisión of CCLmin ± S.D / cm Range / cm ± ± Table 4 shows the mean CCLmin of green turtle females measured during the 2015 Sea Turtle Program. An initial analysis compared carapace length between newly tagged individuals with and without evidence of previous tags; results showed a significant difference (T-test: t = , 32

34 p < ). There was also a difference between newly tagged and previously tagged turtles (Ttest: t = , p < 0.001), so data were analyzed separately. To ensure independence of the data, only the first CCLmin measurement taken for each individual was included in the analysis (See Table 4). CCLmin ranged from cm. Newly tagged turtles with no evidence of previous tags were smaller than newly tagged turtles with evidence or previously tagged turtles (See Table 4). Table 4. Mean CCLmin of green turtles Sample n x ± S.D Range Newly tagged females no evidence ± Newly tagged females with evidence ± Previously tagged females ± Table 5 shows the mean straight carapace length (SCLmax) of green turtles. An initial analysis compared SCLmax between newly tagged turtles with and without evidence of old tags (T-test: t = , p = 0.000); results indicated a significant difference. The second analysis comparing newly tagged and previously tagged turtles also showed a significant difference (T-test: t = , p < ), therefore, data from previously tagged females, new turtles with evidence and new turtles without evidence were analyzed separately (See Table 5). To ensure independence of the data, only the first SCLmax measurement taken for each individual was included in the analysis. SCLmax ranged from cm. Table 5. Mean SCLmax of green turtles Sample n x ± S.D Range Newly tagged females no evidence ± Newly tagged females with evidence ± Previously tagged females ± An analysis comparing the number of eggs laid between newly tagged and previously tagged turtles showed no significant difference (T-test: t = 0.103, p = 0.918), so data were combined for analysis. Only the first nest for each female was included in the analysis, to ensure independence of the data. Table 6 shows the mean clutch size for the 171 nests counted. On 35 occasions females laid yolkless eggs, the number ranged from one to 22. Table 6. Mean clutch size for green turtles n x ± S.D Range ±

35 The precision of CCLmin and SCLmax measurements taken during a single encounter was very similar ( x = 0.5cm and 0.4cm, respectively; See Table 7a). For females encountered and measured on two or more occasions in 2015 precision ranged from cm. CCLmin measurements were taken with higher precision than SCLmax. For both measurements there were occasions when the difference between the length measurements on subsequent encounters with the same female was greater than 5cm; the maximum difference recorded was 6.8cm (See Table 7b). Table 7. Precision of carapace measurements for green turtles a) During the same encounter CCLmin / cm SCLmax / cm n x ± S.D Range n x ± S.D Range 1, ± , ± b) In different encounters Encounters CCLmin / cm SCLmax / cm n x ± S.D Range n x ± S.D Range ± ± ± ± ± ± Hawksbill turtles Carapace measurements were taken for 12 of the 14 hawksbill turtles observed during the 2015 Sea Turtle Program (See Table 8). Data for newly tagged and previously tagged turtles were analyzed separately. CCLmin ranged from cm and SCLmax from cm. Clutch size ranged from eggs (see Table 8). Table 8. Mean carapace length and clutch size of hawksbill turtles Sample CCLmin / cm SCLmax / cm Clutch size / eggs n x ± S.D n x ± S.D n x ± S.D Newly tagged females ± ± ± 20.1 Previously tagged females ± ± Precision of CCLmin measurements of hawksbill females was slightly higher than that of SCLmax measurements (See Table 9); data from newly tagged and previously tagged females 34

36 were combined. Table 9. Precision of carapace measurements for hawksbill turtles CCLmin / cm SCLmax / cm N x ± S.D Range n x ± S.D Range ± ± Determination of Nest Survivorship and Hatching Success Leatherback turtles A total of 31 leatherback nests were marked between 3 April and 23 May, 2015; 11 in Tortuguero and 20 in Jalova. Table 10 shows the fate, hatching and emerging successes of the leatherback nests that were marked and monitored during the incubation period. Table 10. Fate, hatching and emerging success of marked hawksbill nests Fate Tort Jal Total % of nests % Hatching success % Emerging success Undisturbed Poached Eroded Total Tort = Tortuguero; Jal = Jalova Overall mean hatching success of leatherback nests was calculated at 8.8% and emerging success was 8.2%. These values were the mean of the 31 nests that were marked and the fate of the nest was determined (See Table 10). Obviously nests that were poached or eroded had 0.0% hatching and emerging success as all eggs were lost; if these nests are eliminated from the calculations, undisturbed nests had a hatching and emerging success of 54.3% and 50.6%, respectively, which is within the range normally observed for this species. The most serious problem was erosion; 25 nests were lost to high tides, at both ends of the beach. Data from the nest excavations are summarized in Table 11; data are combined from both northern and southern ends of the beach. The incubation period for undisturbed leatherback nests for which emerging was observed (n = 4) varied between days, with a mean of 68 days The distance from the sand surface to the top egg for undisturbed nests at excavation varied between cm with a mean of 73.6cm (n = 28). The distance from the sand surface to the bottom of the egg chamber for the same nests varied from cm, with a mean of 89.6cm. 35

37 Table 11. Summary of data from nest excavations of marked leatherback nests during the 2015 Sea Turtle Program Fate n Hatchlings Live Dead Empty shells Pipped No embryo Unhatched eggs Embryo Full embryo Predated eggs Yolkless eggs Total Undisturbed Total Total = Total number of eggs (excluding yolkless eggs) 36

38 3.5.2 Green turtles A total of 202 green turtle nests were marked between 1 May and 28 September, 2015; 147 nests were marked in Tortuguero and 55 in Jalova. For 18 nests the fate could not be determined with certainty; either they were not encountered at excavation (n = 12), or the tapes were lost (n = 1), or the excavation was not completed (n = 2). For another two nests the excavation could not be conducted as a fresh nest was found close to the site of the marked nest and one excavation included eggs from two different nests. All of these nests (n = 18; 8.9%) were excluded from the analyses, leaving a sample of 184 green turtle nests that were monitored from the date of oviposition until their fate could be determined (See Table 12). A summary of the excavations of the 184 green turtle nests monitored throughout the incubation period is shown in Table 13. Fate Table 12. Fate, hatching and emerging success of marked green turtle nests in 2015 Tort n Jal n Total n % of total Hatching success (%) Emerging success (%) 1. Undisturbed Unhatched Destroyed by another turtle Disturbed by another turtle Predated Partially predated Poached Possibly poached Eroded Partially eroded Possibly eroded Total Nests not included in analysis Tort n Jal n Total n Could not find at excavation One or more tapes removed Incomplete excavation as new nest encountered Excavated two nests together Incomplete excavation Total Tort = Tortuguero (five northern miles); Jal = Jalova (southern three miles); 1 Calculated as the mean of all 67 nests From Table 12 it can be seen that the majority of nests included in the analysis (56.0%, n = 103) remained undisturbed during the incubation period. The majority of disturbed nests were either destroyed or disturbed by another nesting turtle (16.8% in total), or eroded (12.5%). Predation affected 5.4% of nests and 14 nests (7.6%) were poached or possibly poached, all in Tortuguero. 37

39 Table 13. Summary of excavation data for green turtle nests marked in 2015 data combined from Tortuguero and Jalova Fate 1 n Hatchlings Unhatched eggs Empty Pipped Live Dead shells eggs No Full Embryo embryo embryo Depredated eggs Destroyed eggs Yolkless eggs Deformed embryos , Total , For fate code descriptions see Table 13; 2 Includes albino embryos and twins 38

40 Overall hatching success was calculated as 652.1% and overall emerging success was determined as 49.2% (See Table 12). These values were determined as the mean of all 184 marked nests for which the fate could be determined; including those that had 0% success. Undisturbed nests had very high hatching and emerging success (89.7% and 85.8%, respectively). Incubation period, for nests for which hatching was observed (n = 80) varied significantly between Tortuguero and Jalova (T-test: t = , p < ); nests in Tortuguero had a shorter incubation period than those in Jalova. Mean incubation period in Tortuguero was 60 days (Range = days) and in Jalova it was 65 days (Range = days). The mean distance between the sand surface and the top eggshell at the time of excavation for undisturbed nests (n = 103) in Tortuguero was 56.4cm and 63.5cm in Jalova, with a range of 25 91cm and cm, respectively. The mean distance between the sand surface and the bottom of the egg chamber was 68.2cm in Tortuguero and 77.2cm in Jalova, with a range of cm and cm, respectively. Unhatched eggs that contained albino or deformed embryos accounted for only 0.034% of all eggs laid; there were only two albino embryos and two deformed embryos, one without eyes Confiscated eggs In 2015 there were three green turtle nests that were marked that contained eggs confiscated by the police and MINAE officials; two in Tortuguero and one in Jalova. Table 14 shows the fate and success of these three nests. Only one of the nests hatched successfully; one was destroyed by another turtle and eggs from the other showed no evidence of embryo development Table 14. Summary of nests containing confiscated eggs Date Site Fate Hatching success (%) Emerging success (%) 9-Aug Jalova Undisturbed Aug Tortuguero Unhatched Aug Tortuguero Disturbed by another turtle Total Calculated as the mean of all 67 nests Hawksbill turtles Nine hawksbill nests were marked between 4 April 10 September, Table 15 shows a summary of the fate and success of these nests; data are combined from Tortuguero and Jalova. Mean hatching success was 41.4% and emerging success was 37.6% (See Table 15); these values were determined as the mean for all nine nests. Undisturbed nests had much higher hatching and emerging success (74.5% and 67.6%, respectively). Evidence of hatching was observed for five undisturbed nests; the mean incubation period was 62 days, with a range of days. The mean distance between the sand surface and the top eggshell at the time of excavation for undisturbed hawksbill nests (n = 5) was 34.4cm (Range = cm). The mean distance between the sand surface and the bottom of the egg chamber was 50.8cm (Range = 45-58cm). 39

41 Table 15. Summary of hawksbill excavations in 2015 Fate Tort Jal Total % de total Hatching success (%) Emerging success (%) Undisturbed Destroyed by another turtle Poached Eroded Total Fibropapilloma Assessment Tort = Tortuguero; Jal = Jalova; 1 Calculated as the mean of all nine nests A total of 181 green turtles were subject to a thorough examination for the presence of fibropapilloma tumors; no individuals were registered with the disease. In addition to the females who were checked specifically for the presence/absence of fibropapilloma, tumors were also recorded if observed during the routine check for physical abnormalities conducted on all females encountered; seven individuals were found with fibropapilloma tumors on the front flippers or the neck. The largest tumor was 4cm in diameter. Researchers encountered a further 10 turtles that had other types of tumors; the majority on the flippers and neck. These tumors ranged in size from 1 5cm. 3.7 Physical Data Collection Table 16 summarizes rainfall and air temperature data collected from March November, There was a problem with the thermometer in March and April, so it was not possible to measure minimum and maximum temperatures. Table 16. Summary of rainfall and air temperature data March to November, 2015 Month Total rainfall mm / month x rainfall mm / 24 hours Mean temperature / C Temperature range / C March N/A April N/A May June July August September October November Total 4, Air temperature increased between April and June, and then fell during the following three months (See Table 16); mean monthly temperature varied by 1.9 C. March was the coolest month (25.8 C) and October was the warmest (27.9 C). Mean rainfall over a 24 hour period varied considerably 40

42 between March and November, from 6.7mm 27.7mm; August was the wettest month and October the driest (See Table 16). Due to the problem with beach erosion during the first few months of the nesting season, it was impossible to find a suitable place for the sand temperature data loggers on the beach until June. Even then, it was only possible to locate loggers in the border and vegetation zones; those in the border zone were lost to high tide that eroded the beach, so there were only data from those in the vegetation zone at depths of 30 and 50cm (See Table 17). Sand temperature in the vegetation zone ranged from C and mean monthly temperature was almost the same at the two depths (27.1 C and 27.2 C), which is higher than temperatures reported in this zone in other seasons Zone Table 17. Mean monthly sand temperature in 2015 Vegetation x temperature / ºC 3.8 Collection of Human Impact Data Visitors to STC Visitor Centre Border x temperature / ºC N/A = No datalogger at that depth in that month; 1 From 2 June Open x temperature / ºC Depth/ cm April N/A N/A N/A N/A N/A N/A N/A N/A N/A May N/A N/A N/A N/A N/A N/A N/A N/A N/A June N/A N/A N/A N/A N/A N/A N/A July N/A N/A N/A N/A N/A N/A N/A August N/A N/A N/A N/A N/A N/A N/A September N/A N/A N/A N/A N/A N/A N/A October N/A N/A N/A N/A N/A N/A N/A November N/A N/A N/A N/A N/A N/A N/A Mínima N/A N/A N/A N/A N/A N/A N/A Máxima N/A N/A N/A N/A N/A N/A N/A Promedio N/A N/A N/A N/A N/A N/A N/A Visitation to the STC Visitor Center in 2015 increased to 18,304 visitors (See Table 18); more than 2,600 more people than in In all months, with the exception of June, there were more visitors in 2015 than the previous year. The pattern of visitation was similar to that observed previously; most visitors came in January March, with a significant decline starting in April. An increase in visitation was observed in July; this coincides with increased green turtle nesting, which is the major tourist attraction in the area. There was a dramatic decrease in September and October, with an average visitation of just 20 2 people per day (See Table 18). 41

43 Month Table 18. Number of visitors to the STC Visitors Center Total x / day Total x / day Total x / day January 3, , , February 4, , , March 4, , , April 2, , , May June 1, July 1, , , August 1, , , September October November 1, , , December 2, , Total 24, , , Artificial lights A total of seven light surveys were conducted in 2015; two during the leatherback season and five during the green turtle season. The distribution of artificial lights visible on the beach is shown in Figures 11a and 11b; the bars represent the mean number of lights counted in each 1/8 mile during surveys. As can be seen from the two graphs, there was a large decrease in the number of lights visible on the beach during the green turtle season (See Figure 11b), especially the section of beach in front of Tortuguero village. The mean number of lights registered per survey was 99 (Range = ) and 73 (Range = ) for the leatherback and green turtle seasons, respectively. Compared to 2014, there was a decline in the number of lights visible. As in other years, the majority of lights (on average 67.9% in each survey) were recorded between miles 2 6/8 3 3/8. The limit of TNP is in mile 3 3/8; there were no lights within TNP (See Figure 11) Project Red Lights and collaboration with MINAE and ICE In 2015, STC, in conjunction with TNP, initiated a project to try and reduce the quantity of lights from private residences and small cabinas in the village that were visible on the beach. A bulb exchange was conducted in July; white bulbs were changed for amber or red bulbs, which are more turtle/environmentally friendly; fewer white lights were reported during subsequent light surveys. At the end of the season, STC presented a certificate to owners of buildings that had maintained the new lights throughout the year. The results were very position; various houses and cabinas supporting the program, changing their white lights to help sea turtles; two certificates were awarded in December. As in other years, ICE staff continued to help solve the issue of public street lights being visible on the beach. Using the results of a special light survey (when only the street lights were included), it was possible to change the orientation of various problematic lights, so that the light was shining away from the beach. 42

44 Figure 11. Summary of monthly light surveys conducted during the 2015 a) Leatherback nesting season TV ML Limit to TNP SFV TL IIL LL b) Green turtle nesting season TV Limit to TNP SFV TL IIL LL ML Legend: SFV = San Francisco village; TL = Tortuga Lodge, IIL = Ilan Ilan Lodge; LL = Laguna Lodge; ML = Mawamba Lodge; TV = Tortuguero Village 43

45 During 2015, STC held various meetings with ICE and TNP staff to discuss the possibility of implementing a project to change all of bulbs in the public street lights (>20 lights) in Tortuguero to amber LED bulbs. ICE has applied for funds from BID for this project and in October they invited STC to give a presentation to some of the BID personnel, to explain the problem of lights for sea turtles, and share our suggestions on how to resolve this threat. To fully appreciate the situation, the group conducted a walk on the beach at night, to observe the impact of the lights. As a result of this presentation given by STC, and seeing first-hand the obvious need to reduce the threat to sea turtles, after the visit to Tortuguero ICE advised STC that the time frame for the project had been brought forward, and it is scheduled to start in 2016 not 2017 as originally planned Hatchling disorientation There were no incidents of hatchling disorientation events reported during monitoring activities of the 2015 Sea Turtle Program. 3.9 Satellite Tracking Project Three turtles were tracked using satellite telemetry in 2015; two green turtles and one hawksbill. For the second consecutive year it was possible to track a hawksbill, increasing our knowledge about the migration of this species from Tortuguero. The hawksbill was encountered on 2 July; following her release she travelled south, almost to Limón. She stayed in the area until 14 September when she started her migration north, following the Nicaragua costa, and when the transmitter stopped sending signals at the end of October she was located some 100km from the coast. She was tracked for 121 days and travelled a total of 1,723km (1,071 miles). The first green turtle was encountered on 1 July; after her release she stayed close to Tortuguero for several weeks, traveling to Moín beach. She started her migration north at the end of August. Interestingly, she did not stop in Nicaragua as expected, but continued migrating through Central America. She has travelled 2,813km (1,759 miles) and is still located in coastal waters of the Yucatan Peninsula in Mexico. The other green turtle was encountered on 2 July; she also stayed close to the nesting beach for several weeks but at the end of July she headed south, starting her migration. It is the first record of satellite tracked turtle not going north once leaving Tortuguero. She followed the coast of Costa Rica and Panama, to Colombia. She stayed close to the Guajira Peninsula until 31 October. She was tracked for 121 days and swam a total of 1,937km (1,203 miles The migration routes of all three turtles are show on the map in Appendix 5, and they are available online at 4. Discussion 4.1 Preparations The process of applying for the research permit for the 2015 Sea Turtle Program was much slower than lower, causing a delay to the start of monitoring activities until April. To facilitate this and other processes in the future, STC is recommending the formalization of a formal agreement between our organization and SINAC (the National System of Conservation Areas); to strengthen collaboration and support between the two entities. The training and orientation sessions are important for to ensure that all of the RAs and GVI staff are 44

46 well prepared to complete all of the different protocol activities. Everyone received theoretical and practical sessions relating to the monitoring protocol and an introduction to the history and develop;ent of Tortuguero through the years. 4.2 Track Surveys Leatherback turtles Leatherback nesting levels in 2015 were one of the lowest since 1995, when monitoring activities for this species began. One of the most serious problems in 2015 was the severe erosion of large sections of the beach, along the length of the 18 miles of beach. The waves reached the vegetation, causing many trees to fall. It was discouraging to see that leatherback nesting was only observed in six of the weekly surveys, and no more than four nests per survey were recorded. Unfortunately, the problem of very high tides and beach erosion was reported at many nesting beaches along the coast of Costa Rica and also Panama, not only affecting turtles nesting at Tortuguero, therefore leatherbacks did not have access to good quality nesting habitat during much of the year. The weekly and three-day surveys were affected by the high tides during the first few months of the program; on several occasions the surveys were cancelled as it was impossible to walk the beach safe and it was dangerous for researchers. The spatial distribution of leatherback nests in 2015 was typical to that observed in previous years. As in other season, the majority of leatherback nesting was in the southern part of the beach, principally between miles 13 17; there was an obvious increase in the quantity of nests laid in each mile, after mile 13 (See Figure 7) Green turtles The green turtle nesting season started very slowly in 2015; the level of nesting in June was very low, and only started to improve during July (See Figure 3). During June, the beach was still very affected by erosion and high tides, therefore any females coming ashore would not have had a place to nest. However, peak nesting was seen in the middle of August (See Figure 8). Nesting was at a similar level to that in 2014; results of the daily surveys indicated that 18,864 and 18,663 nests were laid in Tortuguero in 2015 and 2014, respectively. Spatial distribution of nesting along the beach was also not typical; weekly surveys showed a peak in mile 11, with another smaller peak in mile 6 (See Figure 5). This atypical pattern was definitely a result of the severe erosion in the section in the middle of the beach where green turtle nesting is normally high. Females were displaced to more appropriate sectors of the beach to be able to nest successfully. The daily track surveys conducted by the FRC 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, level of illegal take of nests and females, and dog predation. The level of nesting was very variable throughout the season; there were some days with very high numbers of nests followed by days with very low levels of nesting (Se Figures 8a and 9a), which is not normal. Interestingly, the temporal distribution of nesting observed from the daily track surveys showed different patterns in the north and south of the beach, as seen in other seasons. In Tortuguero the peak was observed at the beginning of September, while in Jalova the peak was reported in August (See Figure 8b and 9b). 45

47 4.2.3 Other species of turtles 2015 was a poor nesting season for hawksbills; only seven nests were observed during daily track surveys Illegal take Unfortunately, there was illegal take of nests and turtles observed throughout the 2015 Sea Turtle Program. During the weekly surveys there was an increase in the number of turtles taken and nests poached, with 21 turtles taken on just one night in September. The data from the daily track surveys showed that poached was registered on 40.1% of surveys, double the percentage from 2014, with nights when many nests and various turtles were taken from the beach (See Figure 10a). As in other years, the pattern of poaching was very similar, with a peak close to the river mouth (mile - 2/8 2/8) and another just inside TNP at mile 3 4/8 (See Figure 10b). There was also a record of poaching in Jalova for the first time. In comparison to other turtle nesting beaches in Costa Rica, and Central America in general, the level of poaching at Tortuguero continues to be very low (less than 1% of all nests), but as a beach within a protected area it is disappointing that there is no way to completely eliminate this threat Dead turtles Jaguars continued to kill turtles in 2015; 90 green turtles, one leatherback and two hawksbills were encountered. As always, all of the jaguar predation occurred within TNP, between miles 4 2/8 and 17 4/8. Only fresh turtles from the previous night were counted during the surveys, so these values should be considered the minimum number of turtles killed by jaguars Turtles found alive and flipped over STC researchers encountered two green turtles alive and flipped over in the vegetation during 2015 monitoring activities, fewer than the number found in previous years. It is always frustrating to find these turtles, but at least there is the possibility of saving them and helping them return to the sea. In addition to the turtles found flipped over, there were various occasions when turtles were found alive on the trail behind the beach or on the landing strip at the airport (See Appendix 3). With regard to the females found at the airport, they definitely made their way via the entrances used at night during the Turtle Spotter Program for groups of tourists to get on to the beach. On more than one occasion in 2015 STC placed posts at these problematic entrance ways to prevent the passage of turtles but which allowed people to pass through. It was frustrating to discover that these posts were removed within a few days, presumably by guides that were a little annoyed to have their access somewhat restricted. It would be a good idea if TNP could help STC, advising tour guides that these posts are playing a very important function in preventing the access of turtles on to the landing strip; a situation that can cause injury to the turtle (by crawling on the concrete) or an accident if a plane attempts to land if there is a turtle on the airstrip. 4.3 Tagging of Nesting Sea Turtles The period during which night patrols were conducted, from April to the end of October, covers the majority of turtle nesting at Tortuguero and it is suggested that they continue during the same period in future. The number of leatherback encounters in 2015 was less than in 2014, continuing the trend observed 46

48 over the last 13 years; but it was encouraging to observe a slight increase in the percentage of new females; 27.9% compared to 26.7%, respectively. As in other years, the majority of leatherbacks encountered in 2015 had tags when first observed; from Tortuguero or other nesting beaches in the region. These recaptures are very important to show to the Costa Rican authorities the importance of protecting beaches along the length of the coast, including those found outside protected areas, as they reveal that these animals are shared among many locations. It is always encouraging to encounter females with tags from other countries, and in 2015 there were three females with tags that were possibly applied in Mexico; the SD is in contact with researchers there to get more information about these turtles. The goal of tagged 1,000 green turtles was accomplished in 2015; the FRC and RAs conducted various additional patrols to increase the number of encounters with untagged turtles. It is important that the FRC carefully monitors the data throughout the season, to be able to reach the objective of tagging 1,000 new turtles; organizing additional patrols when necessary to tag more turtles. More than 1,700 green turtle encounters were registered in 2015, considerably less than in 2014, but within the range observed in other seasons. As in previous years, the percentage of tagged turtles encountered in Jalova was much lower than in Tortuguero. This may be because we are starting to encounter turtles that have been tagged in Jalova since 2010 when GVI moved there operations base to the southern end of the beach. It will be interesting to see if the percentage of tagged individuals continues to increase in the next few years. As on other occasions, there were few females that were encountered at both extremes of the beach during the season. The overall proportion of turtles encountered with tags was lower than in other years, less than 29% of individuals observed. For another consecutive season, there were many turtles that had been originally tagged more than 10 years ago; 156 females were seen for the first time in Tortuguero more than a decade ago. Additionally, there were eight turtles that were originally tagged more than 20 years previously. The turtle with the longest nesting record observed in 2015 was a female first encountered in 1984, 31 years ago. As always it is good to see that there are a considerable number of older females that return to nest each year, and that there are still plenty of new (untagged) females being encountered; which suggests a balance of different age classes within the Tortuguero nesting population. Turtles encountered with tags from other countries are always exciting, and in 2015 there was one green turtle with tags from a project in Mexico; this turtle also nested at Tortuguero in 2011, which is one of the few records of turtles tagged in other countries that have returned to Tortuguero. These encounters highlight that sea turtles really are a shared international resource, and their investigation, protection and conservation depends good cooperation at all of the habitats that they rely on during their life span. Few encounters with hawksbills (n = 14) were registered in 2015, but the number is within the normal range for this rare species at Tortuguero. It was encouraging to have an opportunity to encounter a loggerhead; this species if very uncommon at Tortuguero, therefor any encounter can help increase our knowledge of their reproductive behavior at this beach. 4.4 Biometric Data Collection Very few leatherbacks were reported with an incomplete caudal projection; a recommendation for the future would be for RAs to record in the field book why they think it is incomplete to ensure that 47

49 everyone is using the same criteria. The overall mean CCLmin (151.2cm) was in the range of values calculated in other seasons and the range of measurements was typical, between cm. This suggests that there is probably a mix of young and old females within the nesting population at Tortuguero; a healthy nesting population should consist of individuals of different ages. The mean CCLmin of green turtles ranged from 104.4cm (newly tagged turtles with no evidence of previous tags NTNE) to 106.2cm (previously tagged turtles PT) and mean SCLmax ranged from 98.8cm (NTNE) to 100.3cm (PT). These measurements were consistent with those obtained for green turtles at Tortuguero in previous seasons, and also showed a typical range of very small and very large individuals (CCLmin: cm; SCLmax: cm). Mean clutch size was 115 eggs, at the upper limit of the normal range calculated for this species in other years. CCLmin and SCLmax measurements were taken with a similar degree of precision, and it is suggested that both measurements continue to be taken for a sample of females nesting at Tortuguero. There was considerable variability in the measurements taken of the same female when observed on more than one occasion (up to 10.5cm difference) and this suggests that the RA training sessions should focus on these data, to emphasize the important of taking all carapace measurements carefully and not simply try to collect all the information as quickly as possible. Also, it is important to check that the measurements are recorded correctly in the field books, to avoid errors at the time of data transcription. 4.5 Determination of Nest Survivorship and Hatching Success Leatherback turtles In 2015 it was possible to mark a high number of leatherback nests (n = 31); 11 in Tortuguero and 20 in Jalova. Unfortunately, the great majority of nests did not hatch; a total of 83.9% were lost, to erosion (80.7%) or poached (3.2%). This resulted in a very low mean hatching and emerging success, only 8.8% and 8.2%, respectively. The five nests that hatched had a hatching and emerging success of 54.3% and 50.6%, within the normal range for this species Green turtles A total of 202 green turtle nests were marked in 2015; 147 in Tortuguero and 55 in Jalova. From these it was possible to determine the fate for 184 (91.1%); as in other years some nests were not found at the time of excavation or two nests excavated together, for example. In 2015 the most serious threats were destruction by another turtle (15.2%) or erosion (12.5%) (See Table 12). It may be that the problem of erosion observed throughout the season reduced the extension of beach available to females; therefore there was an increase in nesting density in the miles with sufficient sand for nesting, so the possibility of a turtle encountering another nest was higher in those sectors. All the nests that were eroded, inundated or destroyed had a success of 0.0%, which greatly affected the calculation of hatching and emerging success (52.1% and 49.2%, respectively) that was very low in comparison to other years. However, the undisturbed nests (56.0% of all marked nests) showed a hatching and emerging success (89.7% and 85.5%, respectively) that was higher than in recent years. The emphasis on nest marking and monitoring during training with RAs in 2015 was also reflected by the observation that evidence of emergence was reported for many nests (n = 80). It was interesting to see that there was a difference in the duration of the incubation between Tortuguero and Jalova (60 days and 65 days, respectively). This difference may be related to the difference in the depth of nests (deeper in Jalova than in Tortuguero); being deeper, the nests in Jalova might have had lower temperatures than those in Tortuguero, that would result in the incubation period being extended by 48

50 several days. Incubation period ranged from days, normal for this species Confiscated eggs There was some confusion with MINAE about the legality of allowing STC researchers to rebury and monitor nests containing eggs confiscated by the police or park rangers. However, when the issue was resolved in 2015, three nests were handed over to STC or GVI staff; two in Tortuguero and one in Jalova. Unfortunately, only one nest showed signs of hatching, with a success of 77.2%. The practice of allowing these eggs to be reburied and monitored is important, as it provides information to MINAE and STC about the correct management of the eggs by the authorities, and it should continue in the future Hawksbill turtles It was possible to mark nine hawksbill nests, of which only five emerged successfully. The rest were destroyed, poached or eroded. The hatching and emerging success of the five nests were 74.5% and 67.6%, respectively. These values are within the typical range for this species in Tortuguero. 4.6 Fibropapilloma Assessment Only seven incidents of fibropapiloma were registered in 2015; but no turtle examined specifically for the presence of fibropapiloma had the disease. Tumors were found during the routine health and body check conducted as part of the data collection process. It is important that the RAs receive sufficient training in how to distinguish FP tumors, that have a distinctive form compared to other types of growths and tumors. There were various females encountered that had other types of tumors, often more than one on an individual, and up to sizes of 5cm in diameter. The revision of females to note such anomalies is very important and should continue in the future, to study the tendency of fibropapiloma and the general health status of the nesting population. 4.7 Physical Data Collection The pattern of environmental conditions observed in 2015 was a little different to that seen in other years, with distinct patterns of rainfall and air temperature, but in general 2015 was a year with a lot less precipitation than Monthly rainfall did not rise above 860mm, compared to a maximum of 1,116.7mm in Less rain also affected air temperature; the average temperature was higher than in This could all be attributed to the climatological phenomenon El Niño, which was affecting climate globally during The high levels of rainfall seen in June, July and August might have affected, not only the temperature, but also the tides that can cause inundation and erosion of nests that were deposited at the end of the leatherback nesting season. The serious problem of erosion at the start of the 2015 Sea Turtle Program resulted in there being no safe location on the beach to place the dataloggers used to measure sand temperature until June. Despite this precaution to wait until the beach appeared sufficiently stable before burying the data loggers, the three that were placed in the border zone were lost, when very high tides eroded enormous quantities of sand within a couple of days. Because of this, sand temperatures were only collected for the vegetation zone in It was interesting to see that temperatures in this zone were higher than normal; this may be due to the fact that the vegetation cover was not as complete as in other years, due to the loss of the majority of shrubs and understory cover when high tides repeatedly entered the vegetation for many consecutive days, killing any plants that were intolerant to salt water. 49

51 4.8 Collection of Human Impact Data It was encouraging to see an increase in visitation to the STC Visitor Center in 2015; more than 2,600 more people entered the center (See Table 18). Our Education and Outreach Coordinator continued to improve the content of the exhibits during 2015 and worked closely with the RAs and Visitor Center administrator to ensure a more enriching experience for visitors. The problem of artificial lights visible on the beach continued throughout 2015, but there were positive results; there was a decline in the number of lights visible over the course of the season. The new Red Lights campaign had good results, with more amber and right lights registered during the last months of the season. These colors are more turtle friendly and don t cause as many problems to nesting turtles or hatchlings leaving the nest. STC is going to continue developing this project in future years, to raise awareness about the threat that artificial lights can have on sea turtles, and at the same time increase the involvement of the community with regard to the conservation of natural resources. The collaboration with ICE to resolve the issue of public street lights was very successful, reflected by a decline in the number of lights visible in front of the village. The news that the ambitious project to change all of the bulbs in the public street lights in Tortuguero to amber LEDs will be initiated in 2016 will be a great achievement and it may be that Tortuguero can become an example to other communities close to turtle nesting beaches in the country. STC will continue to support this ICE initiative. We hope to resolve the problem of the lights in future seasons, by using more friendly light bulbs and the replanting of vegetation behind the beach (to cover the lights). This program should involve various actors, including STC, ICE, TNP and Tortuguero residents. It was very encouraging that there were no reports of incidents of hatchling disorientation during However, this does not necessarily mean that there were no disorientated hatchlings, but that they were not observed during monitoring activities. 4.9 Satellite Tracking Project The three turtles fitted with satellite transmitters during the 2015 Sea Turtle Program will provide valuable information about the migratory behavior of green turtles and hawksbills nesting at Tortuguero. It was interesting to observe that one of the green turtles went to a foraging ground south of Costa Rica; this was the first report in more than a decade of a southerly migration route for this species. We have received news of Tortuguero tags recovered at indigenous communities in the Venezuelan section of the Guajira Peninsula, but never tracked a turtle to that region. Also, it was exciting to attach a transmitter to another hawksbill, to gain more information about the migration routes and foraging grounds of this critically endangered species. This turtle followed a previously observed route, to Nicaraguan waters. Satellite telemetry is a very useful tool for researchers to use to study migration behavior of sea turtles once they leave the nesting beach, and to determine the location of foraging sites, and indicate the potential threats they may face on route to the feeding area, or once they arrive there. Also, it can be a powerful educative tool, providing a means to reach the public and teach them in an entertaining way about science and conservation initiatives. Two of the three turtles tracked in 2015 participated in the Tour de Turtles on-line event, organized by STC, which allows the general public an opportunity to follow the turtles during their migrations, and at the same time, raise awareness about a variety of different threats to sea turtles and their habitats, through each turtle s campaign in the competition. At Tortuguero, hundreds of people, local residents and visitors, could observe the attachment of the 50

52 transmitter and the subsequent release of the turtle back to the ocean. The project, therefore, was very successful, both from a scientific perspective as well as the public outreach opportunity it provided. 5. References Campbell, C.L., Lagueux, C.J., Mortimer, J.A Leatherback turtle, Dermochelys coriacea, nesting at Tortuguero, Costa Rica, in Chel. Cons. Biol. 2(2), 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, Coyne, M., Godfrey, M., Godley, B. & Lay, K Hard shell sea turtle PTT attachment protocol. On-line manual - Troëng, S. & Rankin, E Long-term conservation efforts contribute to positive green turtle Chelonia mydas nesting trend at Tortuguero, Costa Rica. Biol. Conserv. 121,

53 6. Appendices Appendix 1. Photographs showing beach erosion in mile 2 3/8 (close to Mawamba lodge) during several months of the nesting season in

54 Appendix 2. Turtles killed by jaguars in 2015 Date Mile Species Comments 28-Feb 9 4/8 Cm Fresh kill, no tags 4-Apr 8 4/8 Cm Fresh kill, no tags 12 Cm Only pieces of the body were found 7-Apr 15 5/8 Cm Fresh kill, no tags 10-Apr 9 4/8 Cm Fresh kill, no tags 19-Apr 13 Cm Fresh kill, no tags 22-Apr 25-Apr 28-Apr 5 4/8 Cm Fresh kill, no tags 13 Cm Fresh kill, no tags 12 Cm Fresh kill, no tags 12 Cm Fresh kill, no tags 9 4/8 Cm Fresh kill, no tags 12 Cm Fresh kill, no tags 4-May 16 Cm Fresh kill, no tags 7-May 8 4/8 Cm Fresh kill, no tags 13-May 16 6/8 Dc Fresh kill, no tags 25-May 10 Cm Turtle not checked as jaguar was still present 28-May 8 4/8 Cm Fresh kill, no tags 30-May 10 Cm Fresh kill, no tags 8-Jun 16 4/8 Cm Fresh kill 9-Jun 16 1/8 Cm Fresh kill 10-Jun 15 2/8 Cm Fresh kill 12-Jun 16 5/8 Cm Fresh kill 28-Jun 15 2/8 Cm Fresh kill 2-Jul 15 Cm Fresh kill 11-Jul 12 4/8 Cm Fresh kill, no tags 13 4/8 Cm Fresh kill, no tags 18-Jul 11 Cm Fresh kill, tag # Jul 4 4/8 Cm Fresh kill, no tags 21-Jul 4 7/8 Cm Fresh kill, no tags 31-Jul 15 2/8 Cm Fresh kill 3-Aug 4 7/8 Cm Fresh kill, no tags 5-Aug 8-Aug 15 2/8 Cm Fresh kill 16 6/8 Cm Fresh kill 9 4/8 Cm Fresh kill, no tags 14 Cm Fresh kill, no tags 16 4/8 Cm Fresh kill, no tags 53

55 Appendix 2. Continued Date Mile Species Comments 4 2/8 Cm Fresh kill, no tags 15-Aug 5 4/8 Cm Fresh kill, no tags 18-Aug 4 3/8 Cm Fresh kill, no tags 6 Cm Fresh kill, no tags 22-Aug 15 Ei Fresh kill, no tags 26-Aug 4 4/8 Cm Fresh kill, no tags 29-Aug 10 Cm Fresh kill, no tags 1-Sep 4 2/8 Cm Fresh kill, no tags 15 7/8 Cm Fresh kill 3-Sep 16 4/8 Cm Fresh kill 16 6/8 Cm Fresh kill 5-Sep 7 Cm Fresh kill, no tags 10 Cm Fresh kill, no tags 7-Sep 4 7/8 Cm Turtle was not checked 11-Sep 16 5/8 Cm Fresh kill 15-Sep 15 6/8 Cm Fresh kill 18-Sep 16 3/8 Cm Fresh kill 21-Sep 15 5/8 Cm Fresh kill 23-Sep 15 4/8 Cm Fresh kill, no tags 25-Sep 26-Sep 3-Oct 4 4/8 Cm Fresh kill, tag # /8 Cm Fresh kill, no tags 8 Cm Fresh kill, no tags 13 Cm Fresh kill, no tags 13 4/8 Cm Fresh kill, no tags 14 Cm Fresh kill, no tags 14 4/8 Cm Fresh kill, no tags 15 Cm Fresh kill, no tags 15 1/8 Cm Fresh kill, no tags 10 4/8 Cm Fresh kill, no tags 12 Cm Fresh kill, no tags 13 4/8 Cm Fresh kill, no tags 13 4/8 Cm Fresh kill, no tags 14 Cm Fresh kill, no tags 4-Oct 5 Ei Tag #113262, Found by park rangers 5-Oct 16 2/8 Cm Fresh kill 54

56 Appendix 2. Continued Date Mile Species Comments 7-Oct 15 7/8 Cm Fresh kill 8 4/8 Cm Fresh kill, no tags 10-Oct 9 4/8 Cm Fresh kill, no tags 15 4/8 Cm Fresh kill, no tags 12-Oct 16 5/8 Cm Fresh kill 16-Oct 16 2/8 Cm Fresh kill 17-Oct 9 Cm Fresh kill, no tags 9 Cm Fresh kill, no tags 10 Cm Fresh kill, no tags 11 4/8 Cm Fresh kill, no tags 14 4/8 Cm Fresh kill, no tags 15 4/8 Cm Fresh kill 16 Cm Fresh kill, no tags 20-Oct 4 4/8 Cm Fresh kill, no tags 21-Oct 16 4/8 Cm Fresh kill 24-Oct 17 4/8 Cm Fresh kill, no tags 25-Oct 15 5/8 Cm Fresh kill, no tags 28-Oct 17 3/8 Cm Fresh kill 31-Oct 17 Cm Fresh kill, tags #122488/ Nov 9 Cm Fresh kill, no tags 15 4/8 Cm Fresh kill, no tags Cm = Chelonia mydas Green turtle; Dc = Dermochelys coriacea Leatherback; Ei = Eretmochelys imbricata Hawksbill 55

57 Date Appendix 4. Nightly sea turtle encounters for the 2015 Sea Turtle Program Legend New Turtles that had no tags on first encounter in 2015 REM Remigrant turtles that had tags from previous years/other projects on first encounter in 2015 REN Renester turtles that were encountered on more than one occasion during 2015 a) Encounters in the northernmost 5 miles of beach (Tortuguero) Leatherback Green Hawksbill New REM REN Total New REM REN Total New REM REN Total 1-Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr May May May May May

58 Date Appendix 4a. Continued Leatherback Green Hawksbill New REM REN Total New REM REN Total New REM REN Total 6-May May May May May May May May May May May May May May May May May May May May May May May May May May Jun Jun Jun Jun Jun Jun Jun Jun Jun Jun Jun Jun

59 Date Appendix 4a. Continued Leatherback Green Hawksbill New REM REN Total New REM REN Total New REM REN Total 13-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 Jul Jul Jul Jul

60 Date Appendix 4a. Continued Leatherback Green Hawksbill New REM REN Total New REM REN Total New REM REN Total 21-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 Aug Aug Aug Aug

61 Date Appendix 4a. Continued Leatherback Green Hawksbill New REM REN Total New REM REN Total New REM REN Total 28-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 Oct Oct Oct Oct

62 Date Appendix 4a. Continued Leatherback Green Hawksbill New REM REN Total New REM REN Total New REM REN Total 5-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 STT One newly tagged loggerhead encountered on 5 July STT = Sub-total of encounters for Tortuguero 61

63 Date Appendix 4. Continued b) Encounters in the southern 3 miles of beach (Jalova) Leatherback Green Hawksbill New REM REN Total New REM REN Total New REM REN Total 1-Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr Apr May May May May May May May

64 Date Appendix 4b. Continued Leatherback Green Hawksbill New REM REN Total New REM REN Total New REM REN Total 8-May May May May May May May May May May May May May May May May May May May May May May May May Jun Jun Jun Jun Jun Jun Jun Jun Jun Jun Jun Jun Jun Jun

65 Date Appendix 4b. Continued Leatherback Green Hawksbill New REM REN Total New REM REN Total New REM REN Total 15-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 Jul Jul Jul Jul Jul Jul

66 Date Appendix 4b. Continued Leatherback Green Hawksbill New REM REN Total New REM REN Total New REM REN Total 23-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 Aug Aug Aug Aug Aug Aug

67 Date Appendix 4b. Continued Leatherback Green Hawksbill New REM REN Total New REM REN Total New REM REN Total 30-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 Oct Oct Oct Oct Oct Oct

68 Date Appendix 4b. Continued Leatherback Green Hawksbill New REM REN Total New REM REN Total New REM REN Total 7-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 STJ TOTAL A male was encountered and tagged on the beach on 1 August STJ Sub-total of encounters for Jalova; Total Combined total of encounters from Tortuguero and Jalova 67

69 Appendix 5. Migration map of the turtles tracked using satellite telemetry (until September 2015) The blue line is the hawksbill and the pink lines are the green turtles 68