Translocate reptiles away from threats: Snakes and lizards
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.
Due to the number of studies found, this action has been split by species group, though no studies were found for amphisbaenians. See here for: Sea turtles; Tortoises, terrapins, side-necked & softshell turtles; Crocodilians or Tuatara.
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 controlled study in 1995–1997 in site of mixed vegetation in south-east England, UK (Platenberg & Griffiths 1999, same experimental set-up as Nash 2017) found that some slow worms Anguis fragilis translocated away from a development site survived at least two years and bred but had lower body condition compared to wild lizards. At the final release site, 62 of 103 (60%) slow worms were recaptured at least once during the first two years following release (12 males, 25 females, 25 juveniles). Five and zero gravid females were observed in 1996 and 1997 respectively, and two juveniles were presumed to be born at the release site. Translocated lizards had lower body mass for a given length than wild lizards (reported as condition index). Although 136 slow worms were originally captured in a development area and placed in a temporary enclosure, only 103 were recaptured and moved to the final release site. Slow worms (136 individuals) were relocated in 1994 from a housing development site to a 1,000 m2 holding enclosure of grass and scrub with added hibernacula (rubble and log piles). Slow worms were recaptured under sheets of corrugated iron and translocated from July–October 1995 to a 1.7 ha island in a river that was recently cleared of overgrown vegetation; seeded with grass and native trees; and provisioned with log- and vegetation-piles and a new pond. Translocated lizards were monitored from March–October in 1996–1997 (280 visits) using corrugated iron sheets and photographs for identification and compared to a natural population 1.5 km from the island population.Study and other actions tested
A study in 2004–2005 in scrub and grassland in Suffolk, UK (Showler et al. 2005) found that after common lizards Lacerta vivipara were translocated away from a development site to newly constructed artificial hibernacula, lizards were still present six months later. Results were not statistically tested. Six months after lizards were first translocated to the hibernacula, both adult and juvenile lizards were observed basking around each hibernaculum. Three hibernacula (east-west ditches 20 m long, 1 m deep and 1.5 m wide with approximately 70° sloping edges) were constructed and filled with a mixture of drainage pipes, bricks, gravel, rubble, vegetation cuttings, logs and soil in autumn 2004. Plastic piping was added to facilitate lizards entering and entrances restricted in size to limit access by predators such as weasels Mustela nivalis and brown rats Rattus norvegicus (see original paper for details). The hibernacula were 60–120 m away from the development site. Approximately 70 lizards were caught and translocated in autumn 2004 and spring 2005. Lizard use of the hibernacula was monitored from March 2005.Study and other actions tested
A replicated study in 2002–2007 in two sub-tropical urban sites with mixed vegetation in KwaZulu-Natal, South Africa (Armstrong 2008) found that after translocating black-headed dwarf chameleons Bradypodion melanocephalum away from a proposed development, one of two release sites hosted populations larger than the release cohort after five years. During the first year following release, fewer chameleons were found than were released at both sites (site one: 35 released, 3–22 observed; site two: 15 released, 3–12 observed). Two to five years following release, 0–5 chameleons were observed at site one, whereas 10–59 were observed at site two. Chameleons had been observed in both sites prior to the translocation, but a survey of site two in 2002 found no chameleons. In 2002, sixty-eight chameleons were captured in a proposed development area, and 35 were released at site one and 15 at site two. A barrier fence was installed between the development area and release site one. Vegetation was managed in 2004 (both sites) and 2007 (one site, see original paper for details). In 2002–2003, surveys of the specific release locations within each site were carried out at night using a torch (site one: 10 survey nights; site two: 7 survey nights). In 2004–2007, one transect was searched in site one (7 survey nights) and three were searched in site two (7 nights/transect).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 translocation 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 2009–2011 in grazing marshes in Norfolk, UK (Whiting & Booth 2012) found that some adders Vipera berus translocated away from flood defence works to man-made hibernacula bred, returned to the hibernacula to overwinter, and survived for at least eighteen months. Six months after translocation, up to 22 adders/day were recorded on the man-made hibernacula, including one newborn snake. Eighteen months after translocation, 21 of 119 (18%) translocated adders were sighted on or near the hibernacula. In addition, 19 new adders were observed in the vicinity. Viviparous lizards Lacerta vivipara (including juveniles) and grass snakes Natrix helvetica were also recorded on and near the hibernacula 12–18 months after they were built. In September 2009, three hibernacula (100 m approximate length; 1.5 m high, 3 m wide with 45° front and rear slopes) were constructed from natural materials on grazing marshes separated by drainage ditches (see original paper for design details). Each hibernaculum and some of the adjacent grazing area (1 ha total) was enclosed by semi-permanent fencing (plastic sheeting and wooden posts). In March 2010, a total of 119 adders were translocated from nearby flood banks that were subject to flood defence works (which took place May–October 2010). The fencing was opened from mid-May 2010. Adders were monitored in September–October 2010, March–May and July–September 2011.Study and other actions tested
A replicated study in 2008–2010 in dry scrubland in Florida, USA (McCoy et al 2014) found that populations of Florida sand skinks Plestiodon reynoldsi translocated away from a proposed mining site and released into enclosures survived at least three years. Estimates of overall survival of translocated skinks ranged from 49–79%, and 105 of 300 (35%) skinks were recaptured during the two years following release into the enclosures. Provision of shade may have been important in explaining skink survival (reported as model result). Newborn skinks (19 in 2008, 13 in 2009) were captured in all enclosures. A further 35 newborns were trapped in 2010 (unpublished data). Skinks were sourced in spring 2007 from a site scheduled for sand mining and released into fifteen 20 m2 enclosures (20 lizards/enclosure). Enclosures had five experimental treatments (tree only, shade cloth only, tree and coarse woody debris added, coarse woody debris only, control with no shade or debris). Skinks were trapped in enclosures in spring 2008–2009 (16 drift fences and 76 bucket-traps/enclosure), and further trapping was carried out in 2010 (method not given).Study and other actions tested
A replicated study in 2011–2012 in the Orokonui Valley, New Zealand (Knox & Monks 2014) found that some jewelled geckos Naultinus gemmeus translocated away from the threat of illegal collection survived for 14–24 months following release. At least 10 geckos survived for 10 months in a large holding pen following translocation. Fourteen-months after release from the holding pen or release directly into the wild, four penned females (all gravid) were found, and two direct release females (neither gravid) were found. Forty-two geckos were translocated to Orokonui Ecosanctuary from Otago Peninsula (where they were at risk of illegal collection) in December 2011 and January 2012 (21 females, six males and 15 unsexed juveniles) and held in a release pen (10–15 m wide, 55–60 m long and 0.5 m high) until September 2012, at which point the pen was removed. In September 2012, eleven individuals (six females, three males, two unsexed subadults) were released directly at a nearby site (200 m away). Ten penned and nine directly released geckos were monitored by radio tracking (attached using a 22 x 3 cm self-adhesive fabric strip) 1–2 times daily for three weeks.Study and other actions tested
A review published in 2016 of lizard mitigation translocation projects in New Zealand during 1988–2013 (Romijn & Hartley 2016) found that most projects found evidence of breeding following release, but only one found evidence of population growth. Nine of 28 (32%) mitigation translocations had some post-release monitoring. One found evidence of population growth (more lizards found than released), eight found populations were smaller than the number released, and none resulted in complete failure (no lizards found). Only one mitigation translocated was monitored for >5 years, and breeding was observed in this population. Published and unpublished literature were searched, and key people associated with each translocation were identified and contacted for further information. Mitigation translocations were considered those motivated by removing lizards from anthropogenic threats at the donor site, including habitat destruction and illegal collection.Study and other actions tested
A site comparison study in 2013–2015 in two areas of mixed woodland and grassland in Kent, UK (Nash 2017, same experimental set-up as Platenberg & Griffiths 1999) found that a translocated population of slow worms Anguis fragilis was still present 20 years later, and that males at the release site had higher body condition compared to males from another population, but immature slow worms had lower condition. Twenty years after release, a total of 59 slow worms were observed at the release location. Annual population estimates were 74 individuals in 2013, 44 in 2014 and 20 in 2015, and annual survival was estimated at 56% for females and 23% for males. Males at the release site had higher body condition than males from another natural population, whereas immature slow worms at the release site had lower condition than those from the natural population (results reported as condition index). In 1994, a population of 134 slow worms was translocated away from a residential development on a brownfield site and held in a temporary holding enclosure. After one year, 103 slow worms were captures from the enclosure and translocated to small island (1.7 ha) within a river. In 2013–2015, the population was monitored in April–September using artificial cover boards (53 boards: 0.5 m2 each). Monitoring was also carried out at another location with a natural population of slow worms. Size and weight of all slow worms was measured at the time of capture.Study and other actions tested