Breed reptiles in captivity: Snakes – Boas and pythons
Overall effectiveness category Awaiting assessment
Number of studies: 12
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 study in 1977 at the Jersey Zoological Park in Jersey (Bloxam 1977) reported that two of three female Jamaican boas Epicrates subflavus bred successfully in captivity. Two females produced litters of 24 and 34 live young each, with the first litter also containing two stillborn young and an infertile ovum. A third female produced no young. Three female and four male snakes were acquired and housed together in an exhibition enclosure (2.3 x 2.3 x 2.7 m). The substrate was peat and dry leaves; a hollow log and granite boulders were provided; and the air temperature was maintained at 30°C during the day. Young were removed from the main enclosure following birth.Study and other actions tested
A study in 1973–1977 at the Philadelphia Zoological Garden, USA (Groves 1978) reported that emerald tree boas Corallus caninus bred in captivity in two of four years, though some offspring subsequently died. A female produced six live young and four undeveloped ova one year, and one live young, 10 dead young and three undeveloped ova three years later. Two of six snakes from the first brood died within three months of birth, and the one live snake from the second brood died after three months. An adult pair were received in 1973 and housed together with another female emerald tree boa and a pair of green tree pythons Morelia viridis in a fiberglass exhibit (137 x 109 x 239 cm). In 1976, a new captive-bred male emerald tree boa from Fort Worth Zoo was introduced to the female in an exhibit.Study and other actions tested
A study in 1976–1978 at the New York Zoological Park, USA (Holstrom 1980) reported that common anacondas Eunectes murinus bred successfully in captivity. In 1978, two females produced 27 and at least 23 live young each, and a third female produced 28 live and two dead young. Two of the females also produced one undeveloped egg. In 1976–1978, three females and one male were housed together in an exhibit (2.5 x 1.9 x 1.5 m) with a substrate of smooth river gravel and a pool of water. Average air temperatures were 27°C, and a heating coil at one end of the cage provided a thermal gradient of 26–30°C.Study and other actions tested
A study in 1973–1978 in Florida, USA (Fauci 1981) found that three of four Solomon Island ground boas Candoia carinata paulsoni reproduced successfully in captivity in at least one of four years. In 1975–1978, four females produced six litters of 16–33 young, though the number of live young/brood varied from 0–100% and in total, 53 of 141 offspring were stillborn. Females reproduced every other breeding season (years taken from table), and one female died after breeding successfully for the second time. One male and two female snakes were acquired in 1973 and two more females were acquired in 1977. Snakes were housed in two glass-fronted wooden cages (90 x 52 x 62 cm; 2 females/cage) with a substrate of ground, dried corn husk. Cages were kept at ambient temperature and humidity during the breeding season.Study and other actions tested
A study in 1978–1979 in a captive setting [location unknown] (van Mierop & Bessette 1981) found that ball pythons Python regius bred successfully in captivity. Two females produced a clutch of eggs each, and two of four and seven of seven eggs hatched successfully. The incubation period for the first clutch was 63 days. Gravid females were moved to an individual aquarium with a substrate of damp peat moss covered with sphagnum moss Sphagnum sp., and a piece of driftwood for shelter. Humidity was kept at over 90% and ambient temperatures were 26–30°C and 28–32°C. Eggs were left in the aquarium to be incubated within the female’s coils and average coil temperatures were 30.1–30.6°C. One egg that fell outside of the female’s coils and was removed and placed in a glass container with damp peat and sphagnum moss. This container was placed back in the aquarium. After two months, one clutch of eggs was removed and incubated at 30.5°C after they stopped adhering to one another and the female was unable to coil around them.Study and other actions tested
A study in 1978–1979 in the USA (Chiras 1982) found that children’s pythons Liasis childreni bred successfully in captivity. In 1979, a female produced 10 eggs, six of which hatched successfully. Two eggs failed during development, and two were found to contain fully developed but dead young. Incubation periods were 49–52 days, and the six hatchlings survived at least nine months. A pair of adult snakes was acquired in 1978 and housed in separate 35 litre aquaria with a newspaper substrate and a large piece of bark. In late 1978 to early 1979, they were paired for mating multiple times. When gravid, the female was moved to a large fibreglass cage (91 x 45 x 30 cm) with a thermal gradient. Average temperatures were 28°C during the day and 24°C at night. Eggs were placed on potting soil and incubated at 31°C at 100% humidity.Study and other actions tested
A study in 1979–1985 in a number of captive settings in Australia (Charles et al. 1985) found that black-headed pythons Aspidites melanocephalus, water pythons Liasis fuscus, amethystine pythons Morelia amethistina and carpet pythons Morelia spilota all reproduced with some success in captivity. Two of three female black-headed pythons produced clutches of eight and 10 eggs, with 100% and 0% respectively hatching successfully. Hatchlings survived at least 24 months. Two female water pythons produced three clutches of 19, 17 and 16 eggs, and 79, 82 and 100% respectively hatched successfully. Further captive females (at least 7) produced clutches of 6–23 eggs (hatching data not provided). An amethystine python produced a clutch of seven eggs, all of which produced live hatchlings (one egg opened artificially). Three carpet pythons produced clutches of 12, 29 and 11 eggs, and 0, 21 and 100% respectively hatched successfully. Snakes were collected and held in captivity and eggs were either removed and incubated in moist vermiculite or were left in situ for the female to incubate (see paper for details).Study and other actions tested
A study in 2010 in Mini Zoo, Andaman and Nicobar Islands, India (Kumar et al. 2011) reported that a pair of reticulated pythons Python reticulatus bred successfully in captivity. One female python produced a clutch of five eggs, two of which hatched successfully. The hatchlings survived for at least five months. In 2010, a pair of reticulated pythons were housed together in a concrete room (3 x 3 x 3 m). After laying, eggs were left to incubate naturally with the female. Hatchlings were measured after hatching, and again after four and five months.Study and other actions tested
A study in 2008–2010 in a captive setting in Birmingham, UK (Radovanovic 2011) reported that Madagascar tree boas Sanzinia madagascariensis bred successfully in captivity. Two females bred in captivity, with one giving birth to three live young and six infertile eggs, and the second giving birth to five live young, three still-born young and one infertile egg. All eight young snakes survived for at least 6–8 months. In 2008, three tree boas were acquired (two females, one male) and housed individually in enclosures (120 x 60 x 60 cm) with ambient temperatures of 20–28°C and 40–60% humidity. The male was introduced to one female in late 2008–2009, and to the second female in late 2009–2010. All newborn snakes were removed and housed in smaller individual tanks with bark chippings and sphagnum moss Sphagnum sp.Study and other actions tested
A replicated study in 2002–2009 at a commercial breeding company in Utah, USA (Morrill et al. 2011) found that ball pythons Python regius bred successfully in captivity. In 2002–2009, a total of 5,344 eggs from 783 clutches were produced, with an average clutch size 7 eggs/clutch, and an average hatching success of 81%. Adult pythons were housed in individual cages (81 x 43 x 18 cm) with a substrate of wood chips. Ambient temperatures were kept between 21–29.5°C year-round, and a hot-spot was available in each cage that was 32°C during the day and 29.5°C at night. Humidity was maintained at 60%. Females (>1,500 g) were placed in cages with males (>500 g) for 1–2 days, and eggs were moved to Styrofoam boxes (29 x 39 x 18 cm) with a glass lid. Eggs were incubated in one-part perlite to two-parts vermiculite (5:1 mixture with water by volume), and temperatures were maintained at 31.4–31.7°C in 2002–2005, and 30.9–31.1°C in 2006–2009.Study and other actions tested
A review of studies investigating the genetics of captive breeding programmes (Witzenberger & Hochkirch 2011) found that captive breeding reptiles had mixed genetic outcomes in comparison to wild populations. One study found that captive breeding Jamaica boas Epicrates subflavus had a negative effect on genetic diversity (measured as expected heterozygosity and number of alleles) compared to wild populations. Two databases (Web of Science and Zoological Record) were searched for studies investigated the genetics of captive populations up until 2010.Study and other actions tested
A study in 2010 in a captive setting in Birmingham, UK (Radovanovic 2013) reported that Savu Island pythons Liasis mackloti savuensis bred successfully in captivity. One female produced a clutch of nine eggs. Three eggs were infertile, and of the six that were incubated, five hatched successfully. Hatchlings survived for at least eight months. In 2010, one female and three male pythons were acquired. They were housed separately and only introduced to each other for breeding. Ambient temperatures were 29–30°C during the day and 22–25°C at night, and a basking spot at 35°C was provided. Eggs were removed and placed in a plastic box with vermiculite (2:1 mix with water) and incubated at 30°C and 90–100% humidity. Hatchlings were housed individually.Study and other actions tested