Red-eared Slider (Trachemys scripta elegans) Management Plan for Bermuda

Red-eared Slider (Trachemys scripta elegans) Management Plan for Bermuda Government of Bermuda Ministry of the Environment Department of Environment and Natural Resources

Red-eared slider (Trachemys scripta elegans) Management Plan for Bermuda Author This plan was prepared by: Mark E. Outerbridge, PhD. Wildlife Ecologist, Department of Environment and Natural Resources Contact: mouterbridge@gov.bm Cover photo: Red-eared slider by Martin Thomas Published by Government of Bermuda Ministry of the Environment Department of Environment and Natural Resources 2

CONTENTS DISCLAIMER... 5 EXECUTIVE SUMMARY... 6 PART I: INTRODUCTION... 7 A. Historical overview... 7 B. Conservation status... 7 C. Taxonomy and description of species... 7 D. Ecology... 9 Habitat requirements... 9 Feeding... 9 Reproduction and life cycle... 10 E. Current status... 11 Global distribution... 11 Local distribution and abundance... 11 Global impacts... 13 Local impacts... 13 F. Current actions... 13 PART II: MANAGEMENT... 14 A. Management goal... 14 B. Management objectives and criteria... 14 C. Management strategy... 14 D. Tools available for strategy... 15 Trapping... 15 Seine netting... 18 Dip netting... 18 Turning in unwanted pets sliders... 18 E. Step-down narrative of work plan... 19 PART III: IMPLEMENTATION... 21 APPENDIX... 22 REFERENCES... 23 3

LIST OF FIGURES Figure 1. Feral female red-eared slider with green algae on carapace 8 Figure 2. Shell colour variation in feral red-eared sliders from Bermuda...9 Figure 3. Dorsal and ventral views of a hatchling red-eared slider...10 Figure 4. Yellow crowned night heron preying upon a juvenile red-eared slider.11 Figure 5. Map of Bermuda showing known feral populations of red-eared sliders..12 Figure 6. Modified Bermuda lobster trap used to capture red-eared sliders...15 Figure 7. Modified collapsible funnel trap containing red-eared sliders..15 Figure 8. Hoop net used to capture pond turtles...16 Figure 9. Two examples of the sundeck turtle trap designed to capture pond turtles..17 Figure 10. Summer interns examining a seine net for captured red-eared sliders 18 Figure 11. Proposed drop location for unwanted pet red-eared sliders at Jubilee Park (extension) in Pembroke Parish.22 4

DISCLAIMER Management plans delineate reasonable actions that are believed to be required to manage, recover and/or protect listed species. The Department of Environment and Natural Resources (DENR) publishes management and recovery plans, sometimes preparing them with the assistance of field scientists, other government departments, as well as other affected and interested parties, acting as independent advisors to DENR. Plans are submitted to additional peer review before they are adopted by DENR, and formulated with the approval of interested parties mentioned in Parts II and III of the plan. Objectives of the management plan will be attained and necessary funds made available subject to budgetary and other constraints affecting the parties involved. Management plans may not represent the views nor the official positions or approval of any individuals or agencies involved in the plan formulation, other than our own. They represent the official position of DENR only after they have been signed by the Director as approved. Approved plans are subject to modifications as dictated by new findings, changes in species status and the completion of management and/or recovery actions. Literature citation of this document should read as follows: Outerbridge, M.E. 2016. Redeared slider (Trachemys scripta elegans) Management Plan for Bermuda. Department of Environment and Natural Resources, Government of Bermuda. 26 pages. An electronic version of this management plan will also be made available at www.environment.bm 5

EXECUTIVE SUMMARY Current species status: Red-eared sliders are non-native to Bermuda and have been identified as a pest species. Management objectives: The main objectives of this plan is to reduce, by trapping, the number of feral red-eared sliders living in the wild and make legislative reforms that will eliminate them from the local pet trade. These objectives should ultimately lead to the local extirpation of this sub-species on Bermuda. The plan is an evolving document and will be revised periodically. Trapping data will be continually recorded and new methods of removal evaluated for effectiveness. Actions needed: 1. Launch an awareness campaign highlighting the need to manage Bermuda s feral red-eared sliders, 2. Reduce the number of feral red-eared sliders on Bermuda by using a variety of trapping methods, 3. Ban the importation of this genus into Bermuda, 4. Ban the local breeding and sale of this genus on Bermuda, 5. Designate a single pond as a drop-off location for unwanted red-eared sliders. Management costs: The total cost of management and/or recovery actions cannot be defined at this point. Developing budgets for each action are the responsibility of the leading party as outlined in the work plan. 6

PART I: INTRODUCTION A. Historical overview The pond turtle family Emydidae has two species represented on Bermuda; the native diamondback terrapin (Malaclemys terrapin), and the introduced red-eared slider (Trachemys scripta elegans) (Bacon et al., 2006, Parham et al., 2008). Red-eared sliders were first introduced to Bermuda via the pet-trade, and while records do not exist documenting when ornamental pet turtles were first imported, anecdotal evidence suggests that they were being sold in the early 1950s (J. Brady, pers. comm.) It is presently not illegal to import live specimens into Bermuda to be sold as pets; however this sub-species is rarely imported (J. Nisbett, pers. comm.) as there are a number of local breeders who are supplying the demand for these reptiles as pets. Over the last six decades red-eared sliders have escaped from captivity, and unwanted sliders have been deliberately released, which led to this sub-species becoming firmly established in the wild. Red-eared sliders are currently listed as exotic, naturalized and invasive in Bermuda (Kairo et al., 2003; Sterrer et al., 2004) and have nominated by the Invasive Species Specialist Group as among 100 of the "World's Worst" alien invaders (www.issg.org/database). Alien invasive species are considered the main threat to island biodiversity worldwide (Murphy, 2002). Bermuda lacks the diverse suite of North American predators that would naturally keep feral populations of this reptile in check (Dundee and Rossman, 1989; Tucker and Janzen, 1999) which has enabled these feral sliders to grow in abundance on the island over time (D. Wingate pers. comm.) Surveys undertaken in 2005 and 2006 revealed that virtually all fresh water and slightly brackish (salinities 12 practical salinity units) ponds and canals on Bermuda were found to contain feral populations of red-eared sliders existing in densities as high as 981 turtles ha -1 (Outerbridge, 2008). B. Conservation status Red-eared sliders are not protected on Bermuda. C. Taxonomy and description of species Kingdom: Animalia Phylum: Chordata Class: Reptilia Order: Testudines Family: Emydidae Genus: Trachemys Species: scripta Sub-species: elegans 7

Trachemys scripta elegans is one of 14 sub-species belonging to the genus Trachemys. The carapace is oval with a slightly serrated posterior rim and is typically olive coloured with a transverse yellow stripe on each costal scute. This reptile also has distinctive red stripes on the side of the head behind each eye (from which it gets its common name), and narrow chin stripes (Figure 1). The plastron (ventral) scutes are marked with a dark blotch or ocellus on a cream background (Ernst and Barbour, 1989). Shell patterns and colouration are highly variable (Figure 2), and melanism (darkening of the shell and skin) is known to occur in older males (Tucker et al., 1995). The shells of females are typically more domed than in males, which are comparatively flatter. Males have a much longer tail as well as longer fore-claws. This sub-species typically grows to approximately 203 mm carapace length (CL), with a maximum size of 289 mm recorded (Conant and Collins, 1991). Adult female red-eared sliders grow larger than males (Gibbons and Lovich, 1990). Martin Thomas Figure 1. Feral female red-eared slider with green algae on carapace (shell). 8

Anne Glasspool Figure 2. Shell colour variation in feral red-eared sliders from Bermuda. Note the melanism on the males in the center and on the right. D. Ecology Habitat requirements Red-eared sliders are found both in fresh and slightly brackish waters, preferring quiet water with a soft, muddy bottom, abundant vegetation, and suitable basking sites. Individuals can frequently be seen basking on rocks, logs, vegetation masses, and on the banks adjacent to the water (Mount, 1975; Behler, 1979; Dundee and Rossman, 1989; Conant and Collins, 1991). This sub-species is also able to live in urban aquatic environments (Spinks et al., 2003; Teillac-Deschamps et al., 2008). It is worth noting that red-eared sliders can function as a bio-indicator of wetland health (Lamb et al., 1995; Tryphonas et al., 2006). Studies on Bermuda have shown that redeared sliders are negatively impacted by environmental contaminants in the wetlands (particularly trace metals and polycyclic aromatic hydrocarbons). Abnormalities were observed in the liver (i.e. lesions) and in the gonads of both sexes (i.e. segmented testes and necrotic or underdeveloped ovaries) (Bacon et al., 2012). Feeding Red-eared sliders are opportunistic feeders with a highly varied diet (Newbery, 1984; Ernst and Barbour, 1989; Chen and Lue, 1998, Prévot -Julliard et al., 2007). For example, in northern Taiwan and on Bermuda, feral red-eared sliders are known to eat aquatic snails, fishes, adult and larval flies, and some terrestrial insects as well as plant materials and organic pond sediment (Chen and Lue, 1998; Outerbridge, 2008). 9

Reproduction and life cycle Male red-eared sliders typically mature when they reach a plastron length between 90-100 mm (2-5 years of age); females at plastron lengths between 150-195 mm (see Cagle in Ernst and Barbour, 1972). Courtship is highly stereotyped, with males fluttering their long fore claws on and around the face and head of females (Dundee and Rossman, 1989; Jackson and Davis in Lovich et al., 1990). Nests are excavated in friable sand or soil; sometimes considerable distances from water (Mount, 1975). Clutch size can vary from 2-19 eggs, depending upon the size of the female, but typically averages 7-13 (Dundee and Rossman, 1989; Tucker and Janzen, 1998). Eggs are white and measure between 23.5-44.2 mm in length and 18.4-24.6 mm in width (Dundee and Rossman, 1989). As many as five separate clutches may be laid per season. Eggs hatch in approximately 65-75 days and hatchlings usually measure 30-35 mm CL (Dundee and Rossman, 1989; Ernst & Barbour, 1989) (Figure 3). The growth rate of juveniles is rapid during the first few years after hatching. As is the case with other turtles, sex determination of slider hatchlings is temperature dependent; cooler incubation temperatures produce males and warmer temperatures produce females (Lockwood et al., 1991; Ewart and Nelson, 1991; Ewart et al., 1994). Mark Outerbridge Figure 3. Dorsal and ventral views of a hatchling red-eared slider. Predators There are no known predators of adult sliders on Bermuda in the wild; however cane toads (Rhinella marina) and yellow crowned night herons (Nyctanassa violacea) are known to catch and consume hatchlings and small juveniles (Kelehear, 2016; D. Andrade, pers. comm.; M.O., pers. obs.) (Figure 4). Red-eared sliders are occasionally killed on Bermuda s roadways by motorized vehicles (M.O., pers. obs.) 10

David Andrade Figure 4. Yellow crowned night heron preying upon a juvenile red-eared slider. E. Current status Global distribution Red-eared sliders are native to the central U.S.A. from Alabama and Indiana, westward to Kansas, New Mexico and the northeastern states of Mexico (Conant and Collins, 1991); however, this sub-species has been exported via the pet-trade and biological supply industry to numerous countries and areas around the globe. The occurrence of feral populations, as a result of the escape and release of unwanted pet red-eared sliders, is well documented from Australia, South East and Far East Asia, Europe (there are reports from Spain, France, England, Cyprus), the Caribbean, Israel, Bahrain, Mariana Islands, Guam and South Africa (Newbery, 1984; Uchida, 1989; Platt and Fontenot, 1992; da Silva and Blasco, 1995; Luiselli et al., 1997; Chen and Lue, 1998; Cadi et al., 2004.) Local distribution and abundance At least 20 fresh water and slightly brackish ponds and canals, mostly located in the central and western parishes of Bermuda, contain feral populations of red-eared sliders. Those sites include nine ponds in lands designated as either nature reserve or national park under the 1992 Bermuda Development Plan, nine ponds on golf courses, and one 1.75 km drainage canal that runs through a significant part of the industrial area of the city of Hamilton (Figure 5). Estimates of abundance on Bermuda are not available, however between May 2007 and December 2013 894 sliders were trapped and permanently removed from 11 different wetlands (Outerbridge, 2014). Conservative estimates suggest that there are still thousands of feral red-eared sliders remaining and breeding on Bermuda. 11

Figure 5. Map of Bermuda showing known feral populations of red-eared sliders. 12

Global impacts Previous research on alien populations of red-eared sliders in other regions of the globe have suggested that this sub-species may negatively impact some native wildlife, especially native chelonians through competitive dominance and as possible vectors of disease. Exotic red-eared sliders outcompeted the endangered European turtle (Emys orbicularis) and the Western pond turtle (Actinemys marmorata) for preferred basking sites (Cadi and Joly, 2003; Spinks et al., 2003). Populations of the Western pond turtle in Washington State (U.S.A.) were decimated by a respiratory infection during the 1990s thought to have come from introduced red-eared sliders (Hays et al., 1999). Hybridization (or genetic pollution) with other sub-species belonging to the genus Trachemys has also been documented to occur (see Ernst and Jett, 1969; Mitchell, 1994). Furthermore, redeared sliders have been implicated with damaging the eggs and consuming the chicks of some water bird species in the U.K. (Edwards, 2001). Local impacts Over 80% of fresh water wetland nature reserves and national parks on Bermuda contain feral populations of red-eared sliders (Outerbridge, 2008). Many of those nature reserves were created for the preservation of native an endemic species. Red-eared sliders can exist is very high densities in some of the ponds on Bermuda thereby unbalancing the ecology of those ponds. Large red-eared sliders have been locally observed preying on the chicks of water fowl in Pitman s Pond (R. Bascombe, pers. comm.), and sliders are known to cohabit with diamondback terrapins (Malaclemys terrapin), a rare species of pond turtle that is native to Bermuda, in one location. Negative impacts on the latter are currently unknown. F. Current actions The systematic capture and removal of red-eared sliders from the wetlands of Bermuda first occurred in 2001, and was continued in 2003, by summer interns for the Bermuda Biodiversity Project (Linton, 2001; Grant, 2003). Both involved trialling various trap designs and capture techniques. In 2005, the capture efforts continued as part of an assessment of the ecological impacts that feral red-eared sliders might have upon Bermuda s wetland environment (Outerbridge et al., 2007; Outerbridge, 2008). Since 2001, 1532 red-eared sliders have been caught from a variety of wetlands across Bermuda. During the most intensive trapping period (2007-2013) nearly 900 red-eared sliders were captured, 95% of were accomplished using collapsible funnel traps and 5% by using a long-handle dip net (Outerbridge, 2014). Baited funnel traps deployed at the surface of the ponds continues to be the most efficient and effective method of capturing large numbers of red-eared sliders from Bermuda s fresh water wetland environments. 13

PART II: MANAGEMENT A. Management goal The aim of this plan is to reduce, by trapping, the number of feral red-eared sliders living in the wild, make legislative reforms that will eliminate them from the local pet trade, and provide information to the general public about responsible pet ownership of red-eared sliders. This plan is an evolving document and will be revised as needed. Ongoing accomplishments and new information will guide the refinement and revisions of goals and strategies in future versions of the plan. B. Management objectives and criteria These overall objectives translate into specific targets outlined below: Launch an awareness campaign highlighting the need to manage Bermuda s feral red-eared sliders, Reduce the number of feral red-eared sliders on Bermuda by using a variety of trapping methods, Ban the importation of this genus into Bermuda, Ban the local breeding and sale of this genus on Bermuda, Designate a single pond as a drop-off location for unwanted red-eared sliders. C. Management strategy Creating the drop-location for unwanted red-eared sliders (either pets or individuals found wandering) should be given priority in ameliorating the issue of abandoning sliders in Bermuda s wetlands. Providing a pet-friendly pond for unwanted sliders is vital to securing public buy-in when trying to promote responsible pet ownership. The fresh water pond in the Jubilee extension park is centrally located and easily accessible for public convenience, but will require minor modifications (i.e. fenced so that sliders cannot escape). This park is not a key wetland habitat for Bermuda s native and endemic species, and already contains a number of feral red-eared sliders. The periodic removal of sliders would be required to keep the population from growing too large, as would the feeding of the captive animals; however, the public could be involved with the latter. Public outreach should be undertaken at least one year before creating any legislative reforms on the importation, breeding and sale of Trachemys on Bermuda. In the meantime, the continued removal of feral red-eared sliders is planned for the future, with emphasis placed on ponds that are important refuges for Bermuda s threatened native and endemic species. 14

D. Tools available for strategy TRAPPING Funnel trap Two different funnel trap designs were trialed for use in capturing red-eared sliders on Bermuda. The first was made from a standard commercial lobster trap used by Bermudian fishermen to capture spiny lobsters (Panulirus argus), and measured 60 inches in length, 48 inches in width, 24 inches in height with a circular plastic funnel entrance modified to allow sliders entry (Figure 6). The second type of funnel trap trialed for use was a collapsible commercial fish trap made from 0.5 inch vinyl mesh. It measured 32 inches in length, 24 inches in width, 11 inches in height and had a 22 inch wide horizontal opening at both ends through which sliders could enter. Short segments of pool noodle were fitted internally to make the trap buoyant and thus provide a breathing space for trapped sliders (Figure 7). Both types of trap were baited to attract sliders. Anne Glasspool Figure 6. Modified Bermuda lobster trap used to capture red-eared sliders. Mark Outerbridge Figure 7. Modified collapsible funnel trap containing red-eared sliders. 15

Both types of funnel trap caught red-eared sliders, however the collapsible trap design proved to be significantly more effective and easier to transport (see Grant, 2003; Outerbridge, 2008; 2014). Hoop net Typically made from nylon netting of various mesh sizes secured over metal hoops (Figure 8), this style of trap has a fingered throat and ellipsoid or round entrance holes that stretch open when turtles enter the trap. Hoop nets require being tied between two vertical stakes in order to remain open. To permit breathing by trapped turtles, the top portion of the net needs to be above the surface of the water. Baiting is required to attract turtles into the trap. This style of trap has not yet been trialed for use on red-eared sliders in Bermuda, but is reported to be effective in capturing a variety of fresh water turtle species in other regions (see Mali et al., 2014). Internet image Figure 8. Hoop net used to capture pond turtles. Sundeck trap (a.k.a. solarium trap) Floating trap used to catch turtles that haul out of the water to bask in the sun. This style of trap comes in many different designs, but all have the same operating principle; each offers a resting place for turtles that like to bask, therefore baiting is not required. Turtles can easily climb above the water line and access the trap via the inclined ramps located on the sides. Once up the ramp the turtles either slide over a round floating rim (see top image, Figure 9) or crawl onto a trigger board (lower image, Figure 9) which causes them to fall into the holding section. 16

Internet image Anne Glasspool Figure 9. Two examples of the sundeck turtle trap designed to capture pond turtles. All of the turtle traps described above are useful for catching large numbers of sliders and are relatively easy to transport and deploy (particularly the collapsible traps). Limitations include requiring baiting (funnel and hoop traps) to be most effective, risk of being vandalized by the public, and frequent checking to ensure that captured sliders are removed. 17

SEINE NETTING A seine net with mesh small enough to exclude the passage of hatchling-sized red-eared sliders (i.e. 1 cm) can be used in shallow water ponds to capture red-eared sliders. However, O Keeffe (2009) and Linton (2001) reported limited success using this gear. Problems included high escape rates of sliders, entanglement in submerged objects, and a large amount of manpower required to operate the net. Anne Glasspool Figure 10. Summer interns examining a seine net for captured red-eared sliders. DIP NETTING Long-handled dip nets can also be used to capture individual sliders; however they have very limited applications and only work when turtles are in close range to the netter. TURNING IN UNWANTED PETS SLIDERS The Department of the Environment and Natural Resources encourages members of the public to deliver unwanted red-eared sliders to the Bermuda Aquarium Museum and Zoo (BAMZ) rather than abandon them in the wild. Between June 2012 and June 2016, 161 red-eared sliders were taken to BAMZ and humanely euthanized. All were either unwanted pets or animals that had been found wandering. 18

E. Step-down narrative of work plan The required management actions are as follows: 1. Launch an awareness campaign highlighting the need to manage Bermuda s feral red-eared sliders. Actions Proposed: Explain the fact that feral red-eared sliders are non-native to Bermuda and are an alien species within our wetland ecosystems, Describe responsible public behavior with regards to keeping red-eared sliders as pets (i.e. not releasing unwanted siders into the environment). Work Team: Department of Environment and Natural Resources, Society for the Prevention of Cruelty to Animals, Department of Communication and Information Team Leader: Department of Environment and Natural Resources Assistance: Local media outlets Outputs: Media articles 2. Reduce the number of feral red-eared sliders on Bermuda by using a variety of capture methods. Actions Proposed: Continue with using funnel traps, Trial new traps to determine their effectiveness. Work Team: Department of Environment and Natural Resources Team Leader: Department of Environment and Natural Resources (Biodiversity Section) Outputs: Report on the trapping and culling results List of Equipment: Traps, vehicles to transport equipment. 3. Ban the importation of this genus into Bermuda. Actions Proposed: Introduce legislation which prohibits importation. Work Team: Department of Environment and Natural Resources, Attorney General s Chambers Team Leader: Department of Environment and Natural Resources (Animal Management Section) Assistance: Pet stores Outputs: Legislative amendments 19

4. Ban the local breeding and sale of this genus on Bermuda. Actions Proposed: Introduce legislation which prohibits breeding and selling species within this genus. Work Team: Department of Environment and Natural Resources, Attorney General s Chambers Team Leader: Department of Environment and Natural Resources (Animal Management Section) Assistance: Pet stores and members of the public Outputs: Legislative amendments 5. Designate a single pond as a drop-off location for unwanted red-eared sliders. Actions Proposed: Designate the 0.15 acre fresh water pond located in the center of Jubilee Park (extension) as a drop-off location for unwanted red-eared sliders (see Figure 11 in Appendix), Post signage explaining purpose of the pond, Encourage its use by the public through media, Manage the pond to ensure turtles are fed and do not become overcrowded. Work Team: Corporation of Hamilton, Department of Environment and Natural Resources Team Leader: Corporation of Hamilton Assistance: Public Outputs: Media articles, brochures describing responsible pet ownership practices List of Equipment: Fencing and signage for pond 20

PART III: IMPLEMENTATION The table that follows is a summary of scheduled actions for the management programme. It is a guide to meet the various objectives as detailed in the previous section and indicates the priority in scheduling tasks, the agencies responsible for performing the tasks and a time-table for accomplishing the tasks. The following abbreviations are used below: DENR Department of Environment and Natural Resources DCI Department of Communication and Information CoH Corporation of Hamilton AG Attorney General s Chambers SPCA Society for the Prevention of Cruelty to Animals Public members of the general public Priority # Task Description Duration Responsible Party 2 Launch an awareness campaign 1 Describe responsible ownership 1 year DENR, SPCA, DCI 1 Reduce numbers in the wild through capture 2 Continue trapping efforts Ongoing DENR 3 Trial new methods of capture Ongoing DENR Task # 3 Ban importation of genus 4 Introduce legislation which prohibits importation 3 Ban local breeding and sale of genus 5 Introduce legislation which prohibits breeding and sale 1 Create drop-pond for unwanted red-eared sliders 6 Designate pond in Jubilee Park (extension) 6 months DENR, AG 6 months DENR, AG 1 month CoH 7 Post signage 1 month CoH, DENR 8 Encourage use Ongoing DENR, SPCA 9 Manage pond Ongoing DENR, Public 21

APPENDIX Map created by Mandy Shailer Figure 11. Proposed drop location for unwanted pet red-eared sliders at Jubilee Park (extension) in Pembroke Parish. 22

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