Breed reptiles in captivity: Sea turtles

Overall effectiveness category Awaiting assessment
Number of studies: 2
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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.

Study locations

Key messages

Two studies evaluated the effects of breeding sea turtles in captivity. One study was in the Cayman Islands, Costa Rica, Surinam and Ascension Island and one was in Japan.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (2 STUDIES)

Reproductive success (2 studies): One replicated, controlled study in the Cayman Islands, Costa Rica, Surinam and Ascension Island found that artificially incubated green turtle eggs that were laid in captivity had lower hatchling success than those laid in the wild and artificially incubated. One study in Japan reported that hatching success of eggs produced by one female black turtle in captivity was 12%.

BEHAVIOUR (0 STUDIES)

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

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
Referenced paper
Simon M.H., Ulrich G.F. & Parkes A.S. (1975) The green sea turtle (Chelonia mydas): mating, nesting and hatching on a farm. Journal of Zoology, 177, 411-423.
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
Referenced paper
Kawazu I., Maeda K., Fukada S., Omata M., Kobuchi T. & Makabe M. (2018) Breeding success of captive black turtles in an aquarium. Current Herpetology (formerly Acta Herpetologica Japonica 1964-1971 and Japanese Journal of Herpetology 1972-1999), 37, 180-186.

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?

List of journals searched by synopsis

All the journals searched for all synopses

This Action forms part of the Action Synopsis:

Reptile Conservation

Related Actions

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Use holding pens or enclosures at release site prior to release of captive-bred reptiles Action Link	Awaiting assessment	2	Synopsis Link
Head-start wild-caught reptiles for release: Tortoises, terrapins, side-necked & softshell turtles Action Link	Awaiting assessment	18	Synopsis Link
Release captive-bred reptiles into the wild: Snakes & lizards Action Link	Awaiting assessment	10	Synopsis Link