Use hormones and/or other drugs during captive-breeding programmes to induce reproduction/birth
Overall effectiveness category Awaiting assessment
Number of studies: 9
Background information and definitions
Captive animals do not always breed successfully under artificial conditions. Reproductive technologies such as treatment with hormones or other drugs to induce ovulation or sperm production are techniques that can be used in an attempt to increase breeding success by reptiles in captive facilities. It may be appropriate in some circumstances to use hormone or other treatments on wild individuals, for example when it is not desirable to bring them into captivity. Hormone stimulation protocols are often species specific.
Supporting evidence from individual studies
A study in 1989–1992 in a captive setting in the Netherlands (De Bruin & Zwartepoorte 1994) found that egg laying could be induced with injections of calcium and oxytocin in yellow-headed box turtles Cuora aurocapitata. Two females laid two eggs each within two hours of treatment. One female had laid an egg prior to treatment, and the second female laid an additional egg 12 days after treatment. Two of three eggs from one female hatched successfully, whereas none from the other did. In 1989–1990, two pairs of turtles were acquired and males were introduced to both females for mating purposes. Females were injected with calcium (two doses at 60–80 mg/kg, 1–2 h apart) under the skin in the rear leg, followed by 6 IU/kg of oxytocin intramuscularly one hour later.Study and other actions tested
A study in 1998 in a captive setting in New Zealand (Nelson et al. 2004) found that female tuatara Sphenodon punctatus could be induced to lay eggs using oxytocin. A total of 166 eggs from 21 clutches were produced by inducing females with oxytocin (total number of injected females not provided). In 1998, females were induced to lay eggs with an injection of synthetic oxytocin (Oxytocin-s, 10IU/ml).Study and other actions tested
A replicated, controlled study in 1995–2001 in a captive setting in Illinois, USA (King & Stanford 2006) found that inducing gravid plains gartersnakes Thamnophis radix with oxytocin resulted in similar birth success compared to females not induced. Results were not statistically tested. From 18 broods obtained by inducing females with oxytocin, 343 offspring were alive (67%) and 112 stillborn (33%), and from 38 litters obtained with no oxytocin, 473 offspring were alive (79%) and 128 were stillborn (21%). In 1995–2001, gravid females were captured (number not given) and maintained in captivity in individual glass aquaria (40 l) until giving birth. The room was kept at 24–26°C (32°C at one end of aquarium) and humidity at 50%.Study and other actions tested
A study in 2000 on North Brother Island, New Zealand (Mitchell et al. 2006) reported that some tuatara (Sphenodon guntheri) could be induced to lay eggs using oxytocin. Nine of 21 females given oxytocin began to lay clutches of eggs (3–7 eggs/clutch) within 15–70 minutes of receiving the injection. However, eggs from two of those females were small and soft and did not develop successfully. The remaining 12 females did not respond to the oxytocin injection. In 2000, a total of 21 gravid female tuatara received an injection of oxytocin (Oxytocin-s,10 IU/mL) into the body cavity (details of total monitoring time not provided).Study and other actions tested
A replicated, controlled study in 1978–2006 in a laboratory in the USA (Feldman 2007) found that inducing eastern painted turtles Chrysemys picta picta with oxytocin did not affect hatching success when compared to eggs from natural nests, and that 13 turtle species could be induced using oxytocin and arginine vasotocin (AVT) on their own, or in combination with other drugs. Painted turtle hatching success was similar for oxytocin-induced eggs (57 of 62, 92%) and natural nest eggs (58 of 60, 97%). Across 13 turtle species, the number of turtles that laid all eggs after their first injection was 64–97% with oxytocin (0.7–4 units/100 g), 0–50% with AVT (5–50 ng/g), 33–90% with oxytocin and ketamine (<25 or 35 mg/kg), 50% with oxytocin and propranolol (14–38 µg/kg), and 57% with AVT and propranolol (11–14 µg/kg). Sixty painted turtle eggs were collected from wild nests, and 14 turtles were collected before laying and induced with oxytocin (1.4–2.5 units/100 g), yielding 62 eggs. All eggs were incubated in vermiculite. In total, 245 inductions of 13 species of turtle were carried out (1–42 individuals/species): 195 with oxytocin, 22 with AVT and 28 with a combination of drugs. Oxytocin and AVT was injected in to the abdomen and ketamine and propranolol were injected into the shoulder muscle.Study and other actions tested
A replicated, controlled study (years not provided) on four river banks in Illinois, USA (Tucker 2007) found that using oxytocin to induce egg-laying in red-eared sliders Trachemys scripta elegans did not affect the total number of eggs laid. Oxytocin-induced red-eared sliders laid similar numbers of eggs (14 eggs/turtle) to sliders that were not induced (15 eggs/turtle). Female red-eared sliders were collected from four nesting sites by one of two rivers. Twenty-four turtles were found laying natural nests. These turtles were caught, palpated to confirm that egg-laying was complete and eggs were counted in nests. Oxytocin (0.2 ml/kg) was used to induce egg laying in 241 turtles.Study and other actions tested
A replicated study in 2005–2008 in laboratory conditions in South Island, New Zealand (Cree & Hare 2010) found that most wild pregnant common geckos Hoplodactylus maculatus brought into captivity were successfully induced after receiving the hormone arginine vasotocin (AVT). Most (number not given) of the 22 female geckos that received AVT delivered fully developed, viable offspring within 6 h of hormone injection. Pregnant common geckos were collected from the wild in November 2005 and October 2007. Initially, two females that were carrying fully developed embryos well beyond the expected term were induced with AVT (dissolved in 0.8% saline to deliver 150 ng/g of the hormone). A further 20 females that went beyond their expected term were induced.Study and other actions tested
A replicated, controlled, before-and-after study in 1998–2009 in Hainan Province, China (He et al. 2010) found that captive four-eyed turtles Sacalia quadriocellata began reproducing after six years after some individuals received hormone injections, but fertility and hatching success of eggs was low. Results were not statistically tested. In 2004–2008, five of 20 eggs (25%) from hormone-injected females were fertile, compared to 11 of 21 eggs (52%) from females injected with a saline solution (numbers taken from table). In 2008–2009, three of 43 eggs (7%) from females kept in outdoor pools and given no injections were fertile. In 1998, 28 female and 17 male turtles were acquired and kept in indoor pools (60 x 80 cm). In 2004–2007, eighteen females and 12 males were given luteinizing hormone-releasing hormone analogue (females: 8 µg/kg; males 4 µg/kg) and human chorionic gonadotropin (females: 1600 IU/kg; males 800 IU/kg). Hormones were injected into the hind leg muscles every 10 days up to 10 times/year. The remaining 10 females and five males were injected with a saline solution. In 2007–2008, five females and five males were moved to an outdoor pond (10 m2), and in 2008–2009, eighteen females and 12 males were kept in the outdoor pond.Study and other actions tested
A before-and-after study in 2006–2009 in seawater tanks in Okinawa Island, Japan (Kawazu et al. 2014) found that administering a follicle-stimulating hormone (‘FSH’) to captive female hawksbill turtles Eretmochelys imbricata resulted in ovulation and egg formation in all individuals. Following an injection of follicle-stimulating hormone, four female hawksbill turtles ovulated and formed eggshells within 2–4 days. The authors reported that none of the turtles had ovulated in captivity before. In July 2009, four sexually mature female turtles were administered the hormone ‘FSH’ via intra-muscular injection (see original paper for details). Two of the turtles were wild caught in 1996–1998 and were developing follicles/considered sexually mature from 2006 and two were bred in captivity in 1994 and were considered sexually mature from 2008. All turtles were isolated for the year prior to being injected. Turtles were monitored for signs of ovulation using ultrasound.Study and other actions tested
Referenced paperKawazu I., Suzuki M., Maeda K., Kino M., Koyago M., Moriyoshi M., Nakada K. & Sawamukai Y. (2014) Ovulation induction with follicle-stimulating hormone administration in hawksbill turtles Eretmochelys imbricata. Current Herpetology (formerly Acta Herpetologica Japonica 1964-1971 and Japanese Journal of Herpetology 1972-1999), 33, 88-93.