Release captive-bred reptiles into the wild: Sea turtles
Overall effectiveness category Awaiting assessment
Number of studies: 3
Background information and definitions
Captive breeding is normally used to provide individuals that can then be released into the wild (often called ‘reintroduction’) to either re-establish a population that has been lost, or to augment an existing population (‘restocking’).
Release techniques vary considerably, from ‘hard releases’ involving the simple release of individuals into the wild to ‘soft releases’ which involve a variety of adaptation and acclimatisation techniques before release, or post-release feeding and care.
This action includes studies describing the effects of release programmes for captive-bred reptiles that do not specifically test the effectiveness of specific release techniques. For studies that compare specific release techniques see Use holding pens or enclosures at release site prior to release of captive-bred reptiles; Use holding pens or enclosures at release site prior to release of wild reptiles and Release reptiles into burrows.
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: Tortoises, terrapins, side-necked & softshell turtles; Snakes & lizards; Crocodilians or Tuatara.
Supporting evidence from individual studies
A replicated study in 1978–1992 at several sites on the Texan coast of the Gulf of Mexico, USA (Caillouet et al. 1995; same experimental set-up as Caillouet et al. 1995) found that some released captive-bred and reared Kemp's ridley turtles Lepidochelys kempii survived up to 9 years in the wild. Of the 22,608 turtles released, more than 117 were recaptured in the Gulf of Mexico and adjacent bays 1–9 years after release. Recaptured turtles grew by 19–59 cm (straight carapace length) over a period of 1–9 years. In 1978–1992, a total of 22,608 turtles were released into the Gulf of Mexico or adjacent bays, including 18,790 yearlings. Of these yearlings, 18,174 (97%) were released into the Gulf of Mexico, and 616 (3%) into adjacent bays. Turtles were recaptured on an ad-hoc basis by a sea turtle stranding and salvage network and commercial or recreational fishers.Study and other actions tested
A replicated study in 1978–1993 at 13 sites on the Mexican, Texan and Floridian coasts of the Gulf of Mexico (Caillouet et al. 1995; same experimental set-up as Caillouet et al. 1995) found that following large scale releases of captive-bred yearling Kemp’s ridley turtles Lepidochelys kempii, some individuals survived and were recaptured 1–10 years after release. At least 606 turtles survived and were recaptured 1–2 years after release, and at least 59 survived and were recaptured 3–10 years after release. In 1978–1992, a total of 22,255 yearling turtles were released at 13 locations, with 197 released in Campeche, Mexico; 3,268 in west Florida, USA; and 18,174 in Texas, USA. Turtles were recaptured on an ad-hoc basis by a sea turtle stranding and salvage network and commercial or recreational fishers.Study and other actions tested
A replicated study from 1980–2005 in the Cayman Islands and wider Caribbean (Bell et al. 2005) found that some released captive-bred and reared green turtles Chelonia mydas were recaptured as adults throughout the Caribbean, and some were observed successfully nesting. A total of 392 tagged animals were recaptured at intervals of six months to 19 years after release. Of these, 160 were recaptured in the Cayman Island and 232 from elsewhere (2 from Belize, 176 from Cuba, 8 from Honduras, 1 from Mexico, 38 from Nicaragua, 2 from Panama, 4 from USA and 1 from Venezuela). Eight turtles were observed nesting, and two individuals produced clutches of 112 and 110 eggs, with hatching success of 63% and 88%. Rearing occurred at the Cayman Turtle Farm: a commercial turtle meat operation that raised green turtles from captive adults and released excess turtles in to the wild. Eggs were laid on an artificial beach, incubated in a hatchery and then hatchlings reared in groups. Between 1980 and 2001, turtles were released (16,422 hatchlings, 14,347 yearlings and 65 turtles of 19–77 months old) during October–November. Approximately 80% of all turtles released were tagged using a variety of methods (notching, flipper tags and living tags). Recapture information came from intentional and accidental capture by fisheries throughout the Caribbean, stranding networks in the USA, an active recapture effort in 1994 (Cayman Islands) and observations of nesting females.Study and other actions tested