Action

Translocate problem reptiles

How is the evidence assessed?
  • Effectiveness
    not assessed
  • Certainty
    not assessed
  • Harms
    not assessed

Study locations

Key messages

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (6 STUDIES)

  • Abundance (1 study): One global review found that when using recruitment to the adult population as a measure of success, mitigation translocations (of both problem reptiles and moving away from threats) failed more often than those carried out for conservation or research purposes.
  • Survival (5 studies): Two of four controlled studies (including two replicated studies) in Australia, Canada and Hong Kong found that survival of translocated problem tiger snakes and massasauga rattlesnakes was similar to resident snakes for six months or until hibernation. One study found that more translocated problem dugite snakes died within two months than resident snakes. The other study found mixed effects on survival of translocating problem white-lipped pit vipers compared to resident snakes. One controlled study in the USA found that two of seven translocated problem Gila monsters died within 1–24 months of translocation.

BEHAVIOUR (4 STUDIES)

  • Behaviour change (4 studies): Two controlled studies (including one replicated study) in Australia found mixed effects on movement behaviour and home range size of translocating problem tiger snakes and dugite snakes compared to resident snakes. One randomized, controlled study in Canada found that translocated massasauga rattlesnakes moved further from release points after two days than snakes released at their point of capture, but distances were similar after 18 days. One controlled study in the USA found that the home ranges of problem Gila monsters translocated >1 km were similar in size to those translocated <1 km.

OTHER (5 STUDIES)

  • Human-wildlife conflict (5 studies): Three of five controlled studies (including three replicated studies) in the USA, Australia, Canada and Hong Kong of translocations of problem Gila monsters, tiger snakes and western rattlesnakes found that at least some returned to their point of capture or moved in to adjacent suburban areas within a month. One of the studies found that while all problem Gila monsters translocated <1 km returned to their point of capture, none of those translocated >1 km returned. The other two studies found that no massasauga rattlesnakes or problem white-lipped pit vipers returned to their point of capture.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

  1. A controlled study in 2000–2002 in an urban desert setting in Arizona, USA (Sullivan et al. 2004) found that no translocated problem Gila monsters Heloderma suspectum moved >1 km returned to their point of capture, but individuals translocated <1 km all returned. Zero of seven lizards translocated 2–25 km returned to their point of capture, whereas all 18 lizards translocated 0–1 km returned within 1–30 days. Two of 25 died during the 1–24-month monitoring period (1: translocated 2 km, survived 15 months; 2: translocated <1 km, survived 19 months) and five were lost (translocated 7–22 km). Home ranges of long and short distance translocated individuals were statistically similar (long-distance: 8–190 ha; short-distance: 2–37 ha). In 2000–2001, problem Gila monsters were obtained following calls from residents. Lizards were surgically implanted with radio-transmitters and translocated 0–25 km from their point of capture (< 1 km: 18 lizards; > 1 km: 7 lizards). Lizards were located every 2–3 days in March–October and 3–5 days in November–February in 2000–2002.

    Study and other actions tested
  2. A replicated, controlled study in 2002–2003 in a grassy, wooded parkland close to suburban areas in Victoria, Australia (Butler et al. 2005) found that translocated problem tiger snakes Notechis scutatus had similar survival compared to resident snakes but moved longer distances and often returned to surrounding suburban areas. Survival rates were similar for translocated (7 of 8, 88%) and resident snakes (4 of 6, 67%) over six months. Movement between re-sightings of translocated snakes was larger than residents (translocated: 140 m; resident: 64 m) and half of translocated snakes moved out of the release site into adjacent suburban areas within 1–16 days. Translocated snakes had larger home ranges than residents (translocated: 28 ha; resident: 5 ha), but their core ranges (translocated: 1 ha; resident: 1 ha) and total area visited (translocated: 22 ha; resident: 4 ha) were statistically similar. Eight translocated snakes (four females, four males; trapped within 5 km of release site) and six resident snakes (two female, four males; released at point of capture) were released within the 123 ha parkland area. They were surgically implanted with radio transmitters and tracked 2–5 times/week between spring (October) 2002 and autumn (March) 2003.

    Study and other actions tested
  3. A replicated, controlled study in 2004–2005 in one valley of shrubs and coniferous woodland in British Columbia, Canada (Brown et al. 2009) found that short distance translocations of problem western rattlesnakes Crotalus oreganus did not prevent most snakes returning to areas of human activity. Twelve of 14 (86%) translocated snakes returned to the area in which they were captured within an average of 20 days. Snakes returned to areas of human activity 1–7 times each (average of 3). Two snakes from the translocated group were killed by humans (2 of 14, 14%), whereas no mortality was observed in the group of snakes away from humans. In April 2004–August 2005, fourteen adult male rattlesnakes were monitored (by radiotracking) in an area with human activity (235 ha) and 14 were monitored in an area without human activity (235 ha).  When a snake was found in an area of human activity, it was translocated a short distance (average 500 m) to a habitat free of human development. In 2004–2005, snakes were located every two days during the active season (April–October), with five individuals tracked during both years.

    Study and other actions tested
  4. A review of worldwide reptile translocation projects during 1991–2006 (Germano & Bishop 2009) found that translocations carried out because of human-wildlife conflict (mitigation translocations) failed more often than those carried out for conservation or research purposes. Translocations to mitigate impacts of “problem” reptiles and building and development were combined. Projects that translocated animals due to human-wildlife conflicts 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 those used to deal with “problem” animals, as well as building and development mitigation. 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
  5. A randomized, controlled study in 2003 in a temperate forested site in Ontario, Canada (Harvey et al. 2014) found that short-distance translocations did not affect massasauga rattlesnake Sistrurus catenatus catenatus survival.  A similar number of translocated snakes and snakes released at point of capture survived until hibernation (translocated: 4 of 5, 80%; point of capture releases: 8 of 9, 89%). Translocated snakes moved further from their release site after two days (150 m) than snakes released at point of capture (50 m), but distance from release site was similar after 18 days (translocated: 330 m; point of capture: 270 m). No translocated snakes returned to their capture location. Rattlesnakes were captured in July 2003 and translocated either 200 m in a random direction (one female, four males) or released at point of capture (three females, six males). Such short distance translocations are commonly carried out for problem snakes. All snakes were implanted with radio transmitters and relocated every two days for 18 days.

    Study and other actions tested
  6. A replicated, controlled study in 2012–2013 in sites of mixed shrubland and mixed forest in the Hong Kong, China (Devan-Song et al. 2016) found that translocating problem white-lipped pit vipers Cryptelytrops albolabris away from human settlements resulted in lower survival compared to resident snakes in one of two years, but no translocated snakes returned to their point of capture.  In 2012, a similar number of snakes died from the translocated (6 of 8, 75%) and resident (5 of 7, 71%) groups (result was not statistically tested). In 2013, more translocated snakes died than did residents (translocated: 9 of 12, 75%; resident: 3 of 11, 27%). No translocated snakes showed homing behaviour towards their point of capture. Forty-one problem snakes were captured near human settlements and released 3–30 km away. In 2012, translocated snakes were released in a site of mixed shrub and grassland, and in 2013, they were release in a woodland site. Resident snakes were all captured in woodland sites. Vipers were located 1–3 times/week for 18 (translocated) and 31 weeks (resident) in 2012, and 26 weeks (all snakes) in 2013.

    Study and other actions tested
  7. A controlled study in 2015–2017 in a suburban area in Perth, Australia (Wolfe et al. 2018) found that translocated problem dugite snakes Pseudonaja affinis (urban or problem individuals) had larger activity ranges and higher mortality rates than resident snakes. Translocated snakes had larger maximum activity ranges (11 m2/day) compared to resident snakes (1 m2/day). Translocated snakes travelled similar distances (31 m/day) to resident snakes 11 m/day). All translocated snakes died during the study (4 of 4 individuals) compared to half of the resident snakes (3 of 6 individuals). Deaths were caused by predation or road collisions. In total 10 snakes (six resident snakes and four translocated snakes) were tracked for up to 2 months each in September–December 2015–2017. Snakes were either caught opportunistically in urban areas (two individuals) or reported as problem individuals (eight individuals).

    Study and other actions tested
Please cite as:

Sainsbury K.A., Morgan W.H., Watson M., Rotem G., Bouskila A., Smith R.K. & Sutherland W.J. (2021) Reptile Conservation: Global Evidence for the Effects of Interventions for reptiles. Conservation Evidence Series Synopsis. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

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Reptile Conservation

This Action forms part of the Action Synopsis:

Reptile Conservation
Reptile Conservation

Reptile Conservation - Published 2021

Reptile synopsis

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