Breed reptiles in captivity: Sea turtles
Overall effectiveness category Awaiting assessment
Number of studies: 2
Background information and definitions
Captive breeding involves taking wild animals into captivity and establishing and maintaining breeding populations. It tends to be undertaken when wild populations become very small or fragmented or when they are declining rapidly. Captive populations can be maintained while threats in the wild are reduced or removed and can provide an insurance policy against catastrophe in the wild. Captive breeding also potentially provides a method of increasing reproductive output beyond what would be possible in the wild. However, captive breeding can result in problems associated with inbreeding depression, removal of natural selection and adaptation to captive conditions. The aim is usually to release captive-bred animals back to natural habitats, either to original sites once conditions are suitable, to reintroduce species to sites that were occupied in the past or to introduce species to new sites. Some captive populations may also be used for research to benefit wild populations.
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 other species groups.
For studies that investigate the effectiveness of releasing captive-bred reptiles see Release captive-bred reptiles into the wild.
Supporting evidence from individual studies
A replicated, controlled study in 1969–1973 in a captive breeding facility and several sandy beaches in the Cayman Islands, Costa Rica, Surinam and Ascension Island (Simon et al. 1975) found that green turtles Chelonia mydas bred successfully in captivity, but hatching success was generally lower and numbers of infertile eggs higher compared to eggs taken from natural nests. Hatching success for artificially-incubated, captive-laid eggs was 42% (4,800 of 11,300 eggs) compared to 78% (76,000 of 97,300) for artificially-incubated wild-collected eggs and 88% (388 of 442) for undiscovered captive-laid eggs that incubated naturally in the breeding enclosure (result was not statistically tested). Overall, more captive-laid, artificially-incubated turtle eggs were infertile (5,800 of 11,300, 52%) than wild-collected eggs (17,500 of 97,300, 18%). By 1973, a captive facility with a sea-water breeding pool (61 x 27 m) and artificial sandy beach was stocked with 257 green turtles (captive-reared and wild-caught). Eggs laid in nests on the artificial beach (11,300 total eggs) and eggs laid in the wild in natural nests (17,500) on several beaches were collected and incubated in Styrofoam boxes (100 eggs/box, layered with muslin cloth and sand). Average incubation temperature was 28°C. Hatching success from all artificially-incubated eggs and eggs from four undiscovered captive-laid nests (442 total eggs) was evaluated after emergence.Study and other actions tested
A study in 2015–2017 on Okinawa Island, Japan (Kawazu et al. 2018) found that a pair of black turtles Chelonia agassizii bred successfully two years after being moved into a shared enclosure, though hatching success was low. In 2017, a female produced five clutches of eggs, with an average of 45 eggs/clutch. Average hatching success for three clutches laid on land was 12% and incubation periods were 52–57 days. A further two clutches were laid in the water and all eggs were lost. A male and female turtle were acquired in 1999 and 2009 respectively. In 2015, they were both introduced to an outdoor tank (3.5 x 2.2 m) with an open water system. During the nesting season (May–August), the female was moved to a holding tank (17 x 11 x 2 m) that had an open water system and a sandy nesting area. Eggs were collected and moved to a hatchery, where sand temperatures ranged from 27–32°C.Study and other actions tested