Translocate reptiles away from threats: Tortoises, terrapins, side-necked & softshell turtles
Overall effectiveness category Awaiting assessment
Number of studies: 9
Background information and definitions
Translocations are sometimes carried out to remove individuals from specific threats within their range, for example away from development areas (‘mitigation translocation’). Mitigation translocations may be carried out as a preventative measure to protect individuals but have been criticized for prioritising the process of removing individuals above establishing viable populations of translocated individuals in the destination location (Sullivan et al. 2014). A number of issues should be carefully considered before carrying out such translocations, including whether the proposed release site contains suitable habitat; whether the release of additional animals at an occupied site could negatively impact on the resident population; and whether a translocation alone can mitigate the impact of losing suitable habitat due to a development or other threat.
For studies where individuals are relocated for short periods to mitigate risks posed by temporary threats (e.g. habitat management) see Temporarily move reptiles away from short-term threats.
Sullivan B.K., Nowak E.M. & Kwiatkowski M.A. (2014) Problems with mitigation translocation of herpetofauna. Conservation Biology, 29, 12–18
Supporting evidence from individual studies
A replicated study in 1988–1995 in a recovering area of wetland and mixed shrubland, grasses and trees in New York, USA (Cook 2004) found that translocating eastern box turtles Terrapene carolina carolina away from developments and suburban areas resulted in some turtles surviving at least five years and reproducing. Annual survival was estimated at 71%, and of the 53 radio–tracked translocated individuals, 13 (25%) left the site, 25 established home ranges (47%; 17 in the release year, two in year 1, three in year 2, three in year 3) and 15 died (28%). Nineteen gravid females, 11 clutches of 1–9 eggs, and 10 offspring were also found following releases. In 1987–1990, a total of 335 turtles were collected, either from development sites or while crossing roads in suburban areas. Fifty-three turtles were fitted with radio trackers, and were either released immediately, or held in a pen for 15 days prior to release. The remaining 282 turtles were held in pens for 30 days before release. Originally a saltmarsh, the release site was created by dredge spoil deposition during 1928–1945. Radio tagged turtles were located daily for the first three days, then weekly until 1993 (when radio tracking ceased). In 1993–1995, a trained dog Canis lupus familiaris was used to locate turtles.Study and other actions tested
A study in 2001–2003 in a mixed forest site in South Carolina, USA (Tuberville et al. 2005) found that most gopher tortoises Gopherus polyphemus translocated away from a development site survived at least one year after release. Thirty-four of 38 (86%) adult or sub-adult tortoises survived at least one year and the remaining four were lost within 15 days of release. More tortoises stayed at the released site when a release pen was used (9 months penning: 8 of 13, 62% stayed; 12 months penning: 11 of 12, 92% stayed) compared to when no pen was used (3 of 13, 23% stayed). In 2001, tortoises were collected from an industrial development site. Groups of 12–13 adults and sub-adults were assigned either to a soft release penning treatment (9 months or 12 months) or hard release (no penning). All release areas contained starter burrows. All turtles were released in 2002 and relocated in October–November 2002 and March–October 2003. Dispersers were retrieved and re-released at the release site.Study and other actions tested
A replicated, controlled study in 1997–1998 in a site of desert scrub in southern Nevada, USA (Field et al. 2007) found that most desert tortoises Gopherus agassizii translocated away from development areas and held in pens for 2–7 years prior to release survived at least two years after their release. Overall, six of 28 (21%) tortoises died in the first year following release, and no tortoises died in the second year. Mortality rates were similar between tortoises receiving supplementary water (4 of 15, 27%) and those not supplemented (2 of 13, 15%). Released tortoises were held in outdoor pens for two years (juveniles) or seven years (adults) after being removed from areas undergoing urban development. One to two months prior to release, tortoises either received supplementary water (sprinklers on for 15 minutes/day and saucers placed to catch water) (6 females, 8 males, 1 juvenile) or received no water (7 females, 5 males, 1 juvenile). Tortoises were released into artificial burrows in April–May 1997, and the release site was fenced off from a nearby road. Tortoises were relocated by radio-tracking through July 1997 to November 1998.Study and other actions tested
A study in 1994–2008 on a grassy island in Georgia, USA (Tuberville et al. 2008) found that gopher tortoises Gopherus polyphemus translocated away from a development site and provided with a starter burrow had lower initial survival than established tortoises from a previous translocation. Twenty-eight of 76 (37%) newly released tortoises were never recaptured. Initial survival was estimated to be lower for newly released adults (1st year: 75%) compared to for established adults (98%), and lower for newly released immature tortoises (1st year: 45%, 2nd year: 79%) compared to established immature tortoises (84%). In 1994, seventy-four tortoises (23 males, 32 females, 19 unsexed immature tortoises) were translocated from a development site in Georgia, USA. Each was permanently marked with unique notches on the shell and PIT tags and provided with a starter burrow. Between 1987–1993, a total of 25–30 unmarked tortoises of unknown origin were released on the island and not marked until 1994. Turtles were trapped twice a year by bucket or wire traps in autumn and spring from 1994–1998.Study and other actions tested
A review of worldwide reptile translocation projects during 1991–2006 (Germano & Bishop 2009) found that translocations of reptiles away from threats and translocations of ‘problem’ reptiles (mitigation translocations) failed more often than those carried out for conservation or research purposes. Translocations to mitigate impacts of building and development and ‘problem’ reptiles were combined. Mitigation translocations failed more often (63% of 8 projects) than those for conservation purposes (15% of 38) and those for research purposes (50% of 5). Success was independent of the life-stage translocated, number of animals released and geographic region. Mitigation translocations included building and development mitigation as well as those used to deal with “problem” animals. Success was defined as evidence of substantial recruitment to the adult population during monitoring over a period at least as long as it takes the species to reach maturity.Study and other actions tested
A study in 2001–2005 in a site of mixed forest in South Carolina, USA (DeGregorio et al. 2012) found that translocating gopher tortoises Gopherus polyphemus away from a development site to the northerly part of their range resulted in most tortoises surviving the overwinter period. Of 21 tortoises fitted with temperature loggers, all survived the overwintering period. Two tortoises (both immature individuals) that were not fitted with loggers died during the overwintering period. In August–October 2001, a total of 106 tortoises (39 adults, 32 juveniles, 35 hatchlings) were collected from an industrial development site and translocated to an area where they were historically abundant but were absent at the time of translocation. A prescribed burn took place every three years in the release area, with the most recent in spring 2001. Tortoises were released in October 2001 or spring 2002. Twenty-one tortoises were fitted with temperature loggers, which monitored tortoise temperatures during the winters of 2002–2003 and 2004–2005.Study and other actions tested
A replicated, controlled study in 1997–2000 in five sites of desert scrub in Utah, USA (Nussear et al. 2012) found that Agassiz’s desert tortoises Gopherus agassizii translocated away from development areas had similar survival and produced a similar number of eggs as resident tortoises. Overall annual survival was high (94%), and 89% of translocated tortoises (141 of 159) and 85% of resident tortoises (61 of 72) survived for at least 2–3 years. Time spent in captivity (15–2,300 days) did not affect survival (see paper for details). Translocated and resident tortoises produced a similar number of eggs during the study (2–8 eggs/female). Overall, translocated tortoises moved more than residents (translocated: 1,600 m; resident: 600 m). Translocated tortoises were sourced from two facilities used to house tortoises displaced by urban development (held for 15–2,300 days) and 120 individuals were translocated to a total of five sites over three years (17–82 tortoises/year to 1–4 sites in 1997–1998). Translocated tortoises were compared to 72 resident tortoises randomly encountered at two sites in Nevada. All tortoises were marked and monitored weekly using radio telemetry.Study and other actions tested
A controlled study in 2010–2014 in desert scrubland in southern California, USA (Brand et al. 2016) found that Mojave desert tortoises Gopherus agassizii translocated away from an energy plant and held in captivity for two years had similar annual mortality risk, but higher body temperatures in the first year after release, compared to wild resident tortoises. Mortality risk was similar between translocated tortoises (5% mortality/year) and wild resident tortoises (3–5% mortality/year). Translocated tortoises had higher average maximum daily body temperatures (36.8°C) compared to wild resident tortoises (35.9°C) in the first year after translocation and spent more time above 35°C (113 minutes) than resident tortoises (76–84 minutes). Translocated tortoise temperatures were similar to wild resident tortoises in the second and third year after translocation (see paper for details). In October 2010, tortoises were collected from near a thermal energy plant and maintained in captivity until April 2012, when they were released into an 8,798 ha area adjacent to the energy plant (<500 m from the centre of their previous home range). Translocated tortoise survival and body temperatures were compared to resident tortoises in the release area and resident tortoises from two nearby areas with similar habitat (resident tortoises caught for monitoring in spring–autumn 2011). All tortoises (351 total individuals) were radio-tracked in April–September 2012–2014 and a subset (55 translocated, 73 residents in release area, 87 nearby residents) were fitted with temperature loggers which were monitored between April 2012–September 2014.Study and other actions tested
Referenced paperBrand L.A., Farnsworth M.L., Meyers J., Dickson B.G., Grouios C., Scheib A.F. & Scherer R.D. (2016) Mitigation-driven translocation effects on temperature, condition, growth, and mortality of Mojave desert tortoise (Gopherus agassizii) in the face of solar energy development. Biological Conservation, 200, 104-111.
A controlled, before-and-after study in 2012–2016 in mixed scrub and woodland in south-eastern France (Pille et al. 2018) found that Hermann tortoises Testudo hermanni hermanni rescued from developments that were rehabilitated and translocated had similar survival over two years compared to wild tortoises, and tortoises released in spring established home ranges more quickly than tortoises released in autumn. Over two years after release, average survival of rehabilitated, translocated tortoises (83–86%, 24 individuals) was similar to wild tortoises (93–100%, 31 individuals). Autumn-released rehabilitated, translocated tortoises took longer to establish home ranges (258 days) than those released in spring (139 days). Rehabilitated, translocated tortoises settled similar distances from release locations regardless of season of release (see original paper for details). In total, 24 rehabilitated (with various injuries or rescued from urban developments) Herman tortoises were translocated in April 2013 (12 individuals) and October 2013 (12 individuals) and radio tracked. Twenty resident tortoises and 11 from another population were also radio tracked in the release area, and six were tracked from a separate population in 2012–2015.Study and other actions tested