Breed reptiles in captivity: Lizards
Overall effectiveness category Awaiting assessment
Number of studies: 23
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 1970–1979 at the Houston Zoological Gardens, USA (Peterson 1982) reported that Gila monsters Heloderma suspectum bred in captivity and one of two females produced young that survived beyond hatching. In 1979, one female produced four eggs, two of which hatched successfully, though one hatchling was removed from the egg by hand. A second female produced two eggs, one of which hatched successfully, though the hatchling died after one day. Incubation periods ranged from 112–126 days. The remaining three eggs did not develop successfully and were discarded. Five Gila monsters were acquired in 1970–1978, including two females, one male, and two of unknown sex. The lizards were kept together in a glass fronted exhibit (130 x 88 x 140 cm). The average temperature was 28°C, and the lizards were exposed to a UV lamp for 15–20 minutes/day. Eggs were moved to a plastic container (33 x 16 x 8 cm) and incubated in vermiculite (4:1 mixture with water) at 28°C.Study and other actions tested
A study in 1973–1984 at Zurich Zoo, Switzerland (Honegger 1985) reported that prehensile-tailed skinks Corucia zebrata bred successfully in captivity. In 1973–1984, twenty-one skinks were born in captivity, though seven were stillborn. Two young skinks were cannibalised by adults. Skinks were acquired in 1973–1975 from the Bougainville Islands and Solomon Islands. After losing young skinks to cannibalism, gravid females were moved to separate terraria (100 x 50 x 90 cm) containing leaves, peat moss, branches, bark and hollow logs.Study and other actions tested
A study in 1974–1979 in Arizona, USA (Sylber 1985) reported that two species of giant chuckwalla Sauromalus varius and Sauromalus hispidus bred successfully after 2–3 years in captivity. In 1977–1979, two female Sauromalus varius and one female Sauromalus hispidus produced a total of 90 hatchlings from seven broods (5–23 hatchlings/brood). Three of seven clutches of eggs were discovered (19, 21 and 22 eggs/clutch), and the average hatching success was 43% (four clutches remained undiscovered). Five broods were Sauromalus varius (6–23 hatchlings/brood), one was Sauromalus hispidus (5 hatchlings/brood), and one was a hybrid of both species (12 hatchlings/brood). One clutch of 18 undeveloped eggs was discovered that was likely laid in 1976, and 15 eggs that were artificially incubated all failed to hatch. In 1974–1975, two pairs of Sauromalus varius and one pair of Sauromalus hispidus were acquired and housed in an outdoor enclosure (670 x 580 x 120 cm) with natural clay soil covered with 46 cm of desert wash sand. Temperatures ranged from -1–45°C. Fifteen eggs from a clutch discovered in 1977 were removed an incubated at 32°C. Hatchlings were moved to indoor terraria (200 x 100 x 70 cm), with 10 hatchlings/terrarium and temperatures of 25–38°C.Study and other actions tested
A study in 1980–1986 [location unknown] (Chippindale 1991) found that Timor Monitors Varanus timorensis similis bred successfully in captivity and produced hatchlings in two of three years. A female produced one clutch/year of five eggs for three years. Zero eggs hatched from the first clutch, and two eggs from both subsequent clutches hatched successfully (40% hatching success). Incubation periods ranged from 121–140 days, and the four hatchlings survived for at least 2–3 years. In 1980–1981, a wild-caught female and three male monitors were housed in a glass fronted terrarium (195 x 36 x 60 cm) with a newspaper substrate, branches and rocks. Temperatures were 26–30°C during the day and 20–23°C at night. Eggs were moved to a 40 litre aquarium containing 1 cm of water and placed on a raised aluminium screen. The temperature was maintained at 28–30°C, and humidity was 90–100%. Hatchlings were housed individually in 60 litre aquaria with a newspaper substrate and cardboard tubes.Study and other actions tested
A replicated study in 1990–1991 in Texas, USA (Ferguson 1991) found that captive-reared Malagasy panther chameleons Chamaeleo pardalis had low breeding success in captivity. Ten females each produced 1–5 fertile clutches of eggs, and while all fertile eggs developed to full-term young, <10% hatched successfully. Eight of 10 females died within 18 months. Chameleons were housed in fishbowls (1 litre) or aquaria of increasing sizes (8, 13 then 50 litre) as they grew larger. Dead twigs were provided, and temperatures ranged from 30–33°C during the day and 19–23°C at night.Study and other actions tested
A study in 1992–1993 at Dallas Zoo, USA (Card 1994) found that Gould’s monitors Varanus gouldii and Gray’s monitors Varanus olivaceus bred successfully in captivity. In 1992–1993, a female Gould’s monitor produced two clutches/year of 5–10 eggs/clutch. One clutch of five eggs was infertile and hatching success of the other clutches ranged from 50–100%. A female Gray’s monitor produced two clutches/year of 4–8 eggs/clutch, though only a single egg from the first clutch hatched successfully. Females were introduced to a male regularly for several days until courtship or copulation was observed.Study and other actions tested
A study in 1992–1993 on the Arabian Peninsula (Leptien & Böhme 1994) found that a pair of blue-tailed Oman lizards Omanosaura cyanura bred successfully in captivity. In 1993, one female laid five clutches of three eggs and one clutch of 2 eggs. Overall, five of 11 eggs (45%) hatched successfully, and no hatching information was available for two clutches of three eggs each. In 1992–1993, a female and two male lizards were brought into captivity and initially housed together until one male was removed. The terrarium (90 x 40 x 60 cm) contained sand, stones and an Aloe sp. The sand was maintained at 30°C, and during the day temperatures were increased to 60°C for several hours using a spotlight. Eggs were removed and incubated at 28°C.Study and other actions tested
A study in 1985–1995 in Mexico City, Mexico (Gonzalez-Ruiz et al. 1996) found that a pair of Mexican acaltetepons Heloderma horridum bred successfully in one of nine years in captivity. In 1994, a female produced a clutch of 11 eggs, nine of which hatched successfully. Four hatchlings died after two months and five survived for at least one year. Mating activity in three of the previous eight years produced two clutches of one and 15 eggs, none of which developed. An adult pair of lizards were acquired in 1985. Eggs were removed and incubated at 29°C and 95–100% humidity in plastic boxes that were opened daily.Study and other actions tested
A replicated, before-and-after study in 1995–1997 in Texas, USA (McCoid et al. 2005) found that captive curious skinks Carlia ailanpalai produced more clutches of eggs when housed in smaller breeding groups and fed with nutrient rich crickets compared to when they were housed as a single group and fed normal crickets. Results were not statistically tested. When skinks were housed as smaller breeding groups (14 lizards in 4 aquaria and 13 lizards in 3 aquaria) and fed nutrient rich crickets, 76 clutches were produced over 7 months and 16 clutches were produced over 4 months. All clutches from these smaller breeding groups hatched successfully, though hatchlings from one clutch had physical deformities. When 14 skinks were housed in a single aquarium and fed with normal crickets, three clutches of eggs were produced in nine months, one of which hatched successfully. In 1995, eight female and 6 male skinks were received from Guam, Mariana Islands. Skinks were housed in 75 litre aquaria with a substrate of sand or sand and potting soil. Temperatures ranged from 20–32°C, though basking spots at 55°C were available in the aquaria used for smaller breeding groups. Humidity ranged from 60–90%. Nutrient rich crickets were created by feeding crickets with powdered T-Rex® Calcium Plus cricket food.Study and other actions tested
A replicated study in 1997–2000 in Italy (Mattioli et al. 2006) found that successful captive breeding was achieved for lined flat-tail gecko Uroplatus lineatus, day gecko Phelsuma madagascariensis and Standing’s day gecko Phelsuma standingi. Lined flat-tail gecko (4 clutches of 2 eggs/female/year, 93% hatching success, 100% survival to adult), day gecko (8 clutches of 2 eggs/female/year, 95% hatched, 100% survival) and Standing’s day gecko (8 clutches of 2 eggs/female/year, 93% hatched, 100% survived) bred successfully in captivity. The following species laid eggs in captivity, but no information on hatching success was available: Parson’s chameleon Calumma parsonii (1 clutch of 40 eggs/female/year), panther chameleon Furcifer pardalis (6 clutches of 30–50 eggs/female/year) and satanic leaf-tailed gecko Uroplatus phantasticus (3–4 clutches of 2 eggs/female/year, 2). The estimated cost for one captive-bred individual was: €44.50 for either day gecko species, €60.00 for leaf-tailed or flat-tailed geckos and €6.30 for panther chameleons. Animals were imported from Madagascar in 1997–1998 or were obtained from private breeders or other facilities. Reproduction was monitored in captivity over two years. Some data were obtained from private breeders. Costs were calculated for Italy.Study and other actions tested
A replicated study in 1996–2001 in Florida, USA (Regalado 2006) found that seven species of dwarf gecko Sphaerodactylus spp. reproduced successfully in captivity. Twenty-six females from seven species produced an average of 3–9 eggs/year in their first year, and nine females from four species produced 5–12 eggs/year in their second year. Average incubation time for 74 clutches from seven species ranged from 63–86 days. Most individuals of all seven species survived for at least two years. In 1995–2001, geckos were acquired and housed individually or in male-female pairs in plastic containers (2 litres) with a substrate of soil and peat moss, small rocks, leaves and pine bark. Temperatures ranged from 24–33°C in April–October, and 14–23°C in November–March. Eggs were moved to individual plastic containers and placed on sterile soil and peat moss. Incubating eggs were exposed to the same seasonal variations in temperature.Study and other actions tested
A replicated study in 2001–2002 in a laboratory in northern Spain (Santos et al. 2009) found that large psammodromus lizards Psammodromus algirus bred successfully in captivity. Hatching success (2001: 92%; 2002: 87%) and hatchling survival (2001: 91%; 2002: 83%) were high in both years, yielding 178 and 187 juveniles for release in 2001 and 2002 respectively. Adult lizards (29 females and 15 males) were captured in 2001–2002 and housed in terraria (40 x 60 x 30 cm) with a soil substrate and a thermal gradient from 25–50°C. Eggs were placed in plastic cups with 35 g of moist vermiculite (10 g vermiculite: 8 g water) and incubated at 30°C. Hatchlings were placed in a nursery terrarium away from adults. Adults were re-released at their point of capture. Hatchlings were raised for around 49 days in 2001 and 66 days in 2002 before being released in to the wild.Study and other actions tested
A replicated study in 2010–2011 at the Bronx Zoo Department of Herpetology, USA (Baumer et al. 2012) found that almost all eggs from captive common chuckwallas Sauromalus ater hatched successfully following incubation in suspended incubation containers. Three females each produced a clutch (7–9 eggs/clutch), and 23 of 24 eggs (96%) hatched successfully. Incubation periods ranged from 72–74 days following incubation at 31.5°C, to 79–80 days following incubation at 30°C. One egg became mouldy and was removed after 27 days. All 23 hatchlings survived at least 6 weeks following hatching. In 2010–2011, three clutches of seven, eight and nine eggs each were moved to incubation containers, where they were suspended over wet vermiculite. Incubation temperatures were 30, 30–31 and 31.5°C, and humidity was around 100% in all containers.Study and other actions tested
A controlled study (year not provided) in laboratory conditions in the USA (Talent & Talent 2013) found that captive-reared western fence lizards Sceloporus occidentalis bred successfully in captivity, but that more clutches were laid and fewer eggs were infertile when female lizards were housed individually or in pairs compared to in larger groups. Individually-kept females produced more clutches (3.4 clutches laid/female) and fewer infertile eggs (11% infertile eggs/clutch) compared to females kept in groups of four or eight (2.3–2.7 clutches laid/female; 31.4–37.7% infertile eggs/clutch). Female lizards kept in pairs laid similar numbers of clutches (3.1 clutches/female) and infertile eggs (10.6% infertile eggs) to. Clutch sizes, and the proportion of females that laid eggs were similar between different sized groups (see original paper for details). Eggs from wild-caught western fence lizards were hatched and reared in captivity. In total, 96 nine-month-old female lizards were housed either individually or in groups of two/cage, four/cage or eight/cage (24 lizards/treatment) for the breeding season. One male lizard was randomly assigned to each cage for breeding. Eggs were collected from cages within 12 hours of being laid. Females and eggs were monitored until egg-laying ceased and egg fertility was assessed by ‘candling’.Study and other actions tested
A study in 2011–2013 in a captive setting in the UK (Radovanovic 2014) reported that a pair of Rio Fuerte beaded lizards Heloderma exasperatum bred successfully in captivity. One female beaded lizard produced eight eggs in captivity, four of which hatched successfully. From the four eggs that were not successful, one hatchling died during emergence, one died during development, and two were infertile. In 2011, a pair of adult beaded lizards were introduced into an enclosure (3 x 1.5 x 1.5 m) that contained a substrate of sand and sphagnum moss blocks Sphagnum spp. and a range of rocks, branches and plants. Temperatures ranged from 35–40°C in a basking area, and 17–20°C in the rest of the enclosure, and 2 L of water was sprayed each day to increase humidity. Eggs were left to incubate in the enclosure and hatchlings were weighed and moved to separate containers (35 x 20 x 16 cm).Study and other actions tested
A controlled study in 2008–2011 at Los Angeles Zoo, USA (Recchio et al. 2014) found that giant horned lizards Phrynosoma asio bred successfully in captivity, and lower incubation temperatures resulted in longer incubation periods and larger hatchlings. Results were not statistically tested. In 2010–2011, a female produced two clutches of eggs, and 9 of 20 (45%) and 15 of 19 eggs (79%) hatched successfully. In 2011, incubating at 26.5°C rather than 28°C resulted in longer incubation periods (26.5°C: 107–112 days; 28°C: 85–92 days) and larger hatchlings (26.5°C: 1.7–2.1 g; 28°C: 1.4–1.6 g). In 2010, eggs were initially incubated at 31°C but eleven began to wither after a few days. In 2008, one female and two male lizards were housed in a 380 litre tank with a substrate of 80% sand and 20% soil. Temperatures were 28°C, with a basking area at 30–37°C, and 70% humidity. In 2010, eggs were moved to a 3 litre plastic container, placed in vermiculite (4:1 ratio with water by weight), and incubated at 31°C. After a few days the temperature was reduced to 26.5°C and more water was added to the vermiculite (2:1 ratio with water). In 2011, six eggs were incubated at 28°C, and 13 at 26.5°C.Study and other actions tested
A study in 2012–2014 at The Phoenix Zoo, USA (Foster et al. 2015) found that Yuman fringe-toed lizards Uma rufopunctata bred successfully in captivity. In 2013, five clutches of fertile eggs were produced by three female lizards, with an average clutch size of three eggs. Of 14 viable eggs, 13 were incubated and 10 hatched successfully. One egg was damaged during excavation and one clutch of four eggs produced only a single hatchling that died immediately after emergence. Incubation period ranged from 58 days at 31°C to 74 days at 27.5°C. Ten hatchlings survived for at least six months to a year. All females selected nest boxes with an 8:1 sand to water mixture for laying eggs rather than a 16:1 mixture. Four female and three male lizards were acquired in 2012 and maintained in glass tanks (91 x 46 x 43 cm) with a sand substrate and rocks. Temperatures ranged from 43°C under basking lamps to 28°C. Breeding enclosures contained two nest boxes, one containing an 8:1 and the other a 16:1 sand to water mixture.Study and other actions tested
A replicated study in 2009–2014 at Perth Zoo, Australia (McGill 2015) found that banded knob-tailed geckos Nephrurus wheeleri cinctus bred successfully in captivity and some offspring survived for at least a year. Four females produced a total of 40 clutches of eggs over four breeding seasons (2–6 clutches/female/year). The total number of eggs and hatching success was not provided, but authors reported that only one egg failed to hatch. In 2009, eleven geckos were acquired (5 females, 6 males) and housed in four enclosures (88 x 55 x 60 cm), each with a sand substrate, a nesting box and various rocks and branches. Ambient temperatures were 19–26°C with a 31–35°C basking area in summer, and 15–22°C and 24–28°C basking area in winter. Eggs were removed and incubated in perlite or vermiculite (1:1 or 2:1 mix with water) at 29–30°C.Study and other actions tested
A replicated study in 2012–2015 at London Zoo, UK (Harding et al. 2016) reported that tree-runner lizards Plica plica bred successfully in captivity, and one of the captive-bred offspring also went on to bread successfully. One female lizard produced six clutches of eggs (2 clutches/year) over three years and a total of 18 eggs, 11 of which hatched successfully (61%). One of the female captive-bred offspring went on to breed, producing one clutch of two eggs (hatching data not provided). In 2012, one female and two male lizards were acquired and housed in a number of different enclosures, with temperatures ranging from 18–30°C and 33–38.6°C in basking areas. Eggs were removed and placed in plastic containers, partially buried in water-soaked vermiculite, and incubated at 26°C. Hatchlings were placed in a range of difference enclosure types (see paper for details).Study and other actions tested
A study in 2012–2014 in an outdoor enclosure in San Salvador, Bahamas (Hayes et al. 2016) found that housing wild adult San Salvador rock iguanas Cyclura rileyi rileyi together in captivity did result in breeding and egg laying, but only one egg hatched successfully. Six months after bringing wild iguanas into captivity, one young iguana hatched successfully. In the subsequent two years, although gravid females dug burrows and deposited eggs, no hatchlings emerged. A breeding facility was established in May 2012, and eight adult iguanas (3 males and 5 females) were brought into captivity from the wild and housed in an outdoor enclosure (9 x 6 m).Study and other actions tested
Referenced paperHayes W.K., Cyril Jr S., Crutchfield T., Wasilewski J.A., Rothfus T.A. & Carter R.L. (2016) Conservation of the endangered San Salvador rock iguanas (Cyclura rileyi rileyi): population estimation, invasive species control, translocation, and headstarting. Herpetological Conservation and Biology, 11, 90-105.
A replicated study in 1991–2015 in seven zoos in Jamaica and the USA (Wilson et al. 2016) found that Jamaican iguanas Cyclura collei bred in captivity, though most females laid infertile eggs each year. After 24 years of a captive breeding and head-start programme in one Jamaican zoo, five Jamaican iguanas hatched successfully, of which three were released into the wild and two died prior to release. No breeding took place in zoo exhibit cages. After 19–21 years of a captive-breeding programme in American zoos, 73 iguanas hatched successfully. The first hatchling emerged after 6–8 years, but died. Twenty-four hatchlings emerged after 10–12 years and 48 hatchlings emerged after 16–20 years. The authors reported that Jamaican iguanas were less likely to breed in captivity than other captive Cyclura spp. and that in the USA zoos, almost all female iguanas laid infertile eggs annually. In total, 617 Jamaican iguanas were transferred to one zoo in Jamaica (593 individuals in 1991–2015) and six zoos in USA (24 individuals in 1994–2009, see original paper for details) as part of a head-starting and captive-breeding programme.Study and other actions tested
A replicated study in 2009–2016 in two captive-breeding facilities on Christmas Island and at Taronga Zoo, Sydney, Australia (Andrew et al. 2018) found that captive populations of Lister’s geckos Lepidodactylus listeri and Christmas Island blue-tailed skink Cryptoblepharus egeriae increased in size at one captive-breeding facility and remained relatively stable at the other. Results were not statistically tested. On Christmas Island, captive populations of Lister’s geckos grew from 50 in 2012 to 500 in 2016, and captive populations of blue-tailed skinks grew from 150 in 2012 to 750 in 2016. At Taronga zoo, populations of Lister’s geckos (70 in 2011 and 70 in 2016) and blue-tailed skinks (100 in 2011 and 220 in 2016) remained relatively stable. In 2009, all Lister’s geckos and blue-tailed skinks that could be found on Christmas Island were brought into captivity. From these wild-caught individuals and their offspring, 56 geckos and 83 skinks were transported to Taronga Zoo, and the remaining 70 geckos and 109 skinks were maintained at facilities on Christmas Island. Captive management aimed to maximise retention of genetic diversity (see paper for more details).Study and other actions tested
Referenced paperAndrew P., Cogger H., Driscoll D., Flakus S., Harlow P., Maple D., Misso M., Pink C., Retallick K., Rose K., Tiernan B., West J. & Woinarski J.C.Z. (2018) Somewhat saved: a captive breeding programme for two endemic Christmas Island lizard species, now extinct in the wild. Oryx, 52, 171-174.
A replicated study in 2016–2017 in New South Wales, Australia (Hansson & Olsson 2018) found that Australian painted dragons Ctenophorus pictus bred successfully in captivity, and that hatching success was not affected by incubation temperature but was higher during the early breeding season. Females produced 1–4 clutches, with an average of 4 eggs/clutch. Overall hatching success was 60% (66 of 110 eggs) and hatching success was similar across all incubation temperatures (68% at 28°C; 56% at 30°C; 57% at 32°C). In addition, hatching success was higher for eggs laid earlier in the season (data presented at statistical model results). Wild-caught dragons were housed as breeding pairs in cages (50 x 40 x 35 cm) with a sand substrate, basking area, and sandy area for egg laying. Temperatures fluctuated between 15–25°C. Eggs were removed (110 eggs from 19 females) and placed in individual plastic cups (125 ml) in moist vermiculite (1:5 ratio with water by volume), and the cups were sealed with plastic cling wrap and a rubber band. Eggs from each clutch were split evenly between three incubation temperatures: 28, 30 or 32°C (110 eggs overall). Eggs were checked daily and those that failed during incubation were removed.Study and other actions tested