Action: Captive breeding toads
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- Ten replicated studies (including three small studies) in Germany, Italy, Spain, the UK and USA found that toads produced eggs in captivity, in one case by second generation captive females. Eight found that captive-bred toads were raised successfully to tadpoles, toadlets or adults in captivity. Two found that most toads died after hatching or after metamorphosis. Two reviews found mixed results with four species of toad or 21% of captive populations of Puerto Rican crested toad breeding successfully in captivity.
- Four replicated studies in Germany, Spain and the USA found that reproductive success of captive toads was affected by tank humidity or was higher in outdoor enclosures than indoor tanks. One replicated study in Germany found that survival of European red-bellied toad eggs, tadpoles and juveniles was higher in captivity than the wild.
Supporting evidence from individual studies
A small, replicated study in 1973–1974 of captive Colombian giant toads Bufo blombergi at Brownsville Zoo, USA (Burchfield 1975) found that toads reproduced successfully in captivity. Three months after being housed together, one male started calling and one of three females produced eggs. Of the few eggs that were fertile (separated prematurely by keepers), five hatched and two tadpoles survived metamorphosis, dying at day 68 and 173. The following year one female produced eggs that hatched into approximately 600 tadpoles. Five male and three female toads were housed together. Eggs were placed in spring water at 19°C and tadpoles in spring water with sphagnum moss.
A small, replicated study in 1981–1984 of captive natterjack toads Bufo calamita in Norfolk, UK (Jones 1984) found that two egg strings were produced by nine females. These hatched successfully. The majority of the tadpoles were released back to the wild. In the first year only one of nine wild toadlets survived overwintering in captivity and died shortly after. The following year all 25 wild tadpoles survived to adulthood. In 1981, 12 and in 1982, 25 tadpoles were collected from the wild. Toadlets were housed in a tank with water, a sloping sandy substrate and moss. In the first year toadlets were housed outdoors, after that all tadpoles were kept indoors for at least their first year. Adults were housed in an outdoor enclosure with sandy substrate, a pool, wood and heathland plants.
A review of captive breeding programmes (Maruska 1986) found that a number of amphibian species have been bred successfully in captivity. Toad species that were bred successfully were: Surinam toad Pipa pipa, Colombian giant toad Bufo blombergi, Houston toad Bufo houstonensis and Puerto Rican crested toad Peltophryne lemur.
A replicated study in 1984–1989 of captive Puerto Rican crested toads Peltophryne lemur in Toronto Zoo, Canada and Buffalo Zoo, USA (Johnson & Paine 1989) found that they bred successfully in captivity. Over 3,000 captive-bred toadlets and 12 two-year old toads were released and 400 toadlets sent to other zoos. A small land area or ‘beach’ was created at one end of each tank by slowly reducing the water level, to simulate pond drying. Shelter habitat, such as halved coconuts, were provided for emerging toadlets to prevent dessication.
A small, replicated study in 1988–1990 of captive common midwife toads Alytes obstetricans in Norfolk, UK (Billings 1991) found that nine egg strings were produced from two captive females. Strings contained 14–32 eggs, less than three per batch were infertile. Toadlets were observed leaving the water from at least the first five batches. One female was introduced to a number of males in 1988 and 1990. Toads were housed in an outdoor enclosure (120 x 75 cm) with sandy soil, wood, plants and a small pool. Tadpoles were moved to separate tanks.
A review in 1994 of captive breeding programmes for the Puerto Rican crested toad Peltophryne lemur (Johnson 1994) reported that the species had bred at three of the 14 zoos and institutions with captive populations.
A study in 1993 of a captive European fire-bellied toad Bombina bombina in England, UK (Wilkinson 1994) found that 94 tadpoles hatched from eggs produced by the one captive female. A total of 52 toadlets survived at least one month after metamorphosis. Deaths were largely due to cannibalism. Two male and one female toad were obtained from the wild in 1993. They were housed in a 60 x 30 cm tank with aquatic plants and shelters. The water depth was increased from 8 to 25 cm for breeding. Adults were removed following hatching.
A replicated study in 1991–1994 of Wyoming toads Bufo hemiophrys baxteri in a zoo in Colorado, USA (Burton et al. 1995) found that breeding was moderately successful in field enclosures but in captivity although females produced eggs, tadpoles did not survive. Protected breeding pens in the field were considered by the authors to be moderately successful. In captivity, five of seven hormonally induced females produced thousands of fertile eggs in 1994. However, the majority of tadpoles that hatched died within 72 hours. Deaths were considered by the authors to have been due to water quality. In captivity, two to four wild-caught and captive-bred toads were housed per tank (40 x 61 x 23 cm) at 20°C. Cork bark, sheet moss, sand, water, artificial plants and a basking lamp were provided. In 1991–1993, toads were transported to breeding enclosures at the edge of the lake. In 1994, five toads were overwintered for six weeks at 4.5°C. Seven females were hormonally induced and paired in captivity.
A replicated study in 1999–2003 of captive European red-bellied toads Bombina bombina in northern Germany (Kinne, Kunert & Zimmermann 2004) found that toads bred successfully, particularly outdoors where they were more active, started calling earlier and had higher reproductive success than those indoors. In 2001, 20 indoor females produced an average of 31 eggs/batch (range: 15–40), compared to a total of 1,100 eggs from three outdoor females. Mortality of eggs (8–20%; n = 380), tadpoles (4–7%; n = 1,680) and juveniles (8%; n = 250) was lower in captivity than the field. However, disease could kill all juveniles within 3–5 weeks. Few adults died in captivity, with some living 12 years. All toads successfully over-wintered (at 4–7°C). Breeding enclosures were glass tanks (150 x 60 x 60 cm) with aquatic and terrestrial areas, each housing two adult males and 3–5 females. Eggs were moved to plastic dishes and then outdoor aquaria for hatching. Metamorphs were moved to tanks (60 x 30 x 30 cm). Day temperature was increased to 21°C and daylight periods lengthened to induce breeding.
A replicated study in 2000–2006 of Kihansi spray toads Nectophrynoides asperginis at zoos in the USA (Lee et al. 2006) found that toads bred successfully in captivity. Within the first six months, 82% of 269 founders and 43% of toadlets died. However, by 2006 this captive population was 159 toads. A total of 401 toadlets were born in the first year, with second generation toads born the following year. A second captive population of 230 founders initially doubled, declined to 32 toads and then increased to 130 by 2006. Ceasing or reducing misting inhibited reproductive activity. Primary diseases were lungworm infection and Gram-negative septicaemia; other health issues were also recorded. In November 2000, 499 adults were collected from the one remaining wild population. Following quarantine, the 269 toads maintained at Bronx Zoo were separated into 13 groups of 20–31 toads. Aquaria (38–76 L) were misted 4–9 times/day. Toadlets were transferred into smaller aquariums. The other 230 toads were transported to the National Amphibian Conservation Center (three zoos).
A replicated study in 2006–2011 of captive common midwife toads Alytes obstetricans near Madrid, Spain (Martín-Beyer et al. 2011) found that toads bred successfully. Housing adults outdoors, under semi-captive conditions, was most effective for achieving mating. Over 180 tadpoles were produced in captivity. Tadpoles were collected in the wild and treated against the chyrtid fungus using elevated temperature (> 21°C) and baths in antifungal drugs (itraconazole). Tadpoles were reared in indoor aquariums in similar environmental conditions to the wild.
A replicated study in 2008–2011 of captive Apennine yellow-bellied toads Bombina variegata pachypus at the University of Genoa, Italy (Canessa 2012) found that by 2011 the captive breeding programme had succeeded in raising several tadpoles to metamorphosis. The plan was to go on to release animals to purpose-built breeding sites.
- Burchfield P.M. (1975) Breeding the Colombian giant toad Bufo blombergi at Brownsville Zoo. International Zoo Yearbook, 15, 89-90
- Jones M. (1984) Captive rearing and breeding of Norfolk natterjacks, Bufo calamita. Herpetological Society Bulletin, 10, 43-45
- Maruska E.J. (1986) Amphibians: review of zoo breeding programmes. International Zoo Yearbook, 24/25, 56-65
- Johnson B. & Paine F. (1989) The release of Puerto Rican crested toads: captive management implications and the cactus connection. Regional Meetings of the American Association of Zoological Parks and Aquariums, 962-967.
- Billings D. (1991) Keeping and breeding the midwife toad (Alytes obstetricans) in captivity. British Herpetological Society Bulletin, 35, 12-16
- Johnson R.R. (1994) Model programs for reproduction and management: ex situ and in situ conservation of toads of the family Bufonidae. Pages 243-254 in: J.T. Collins, K. Adler & J.B. Murphy (eds.) Captive Management and Conservation of Amphibians and Reptiles, Contributions to Herpetology Vol. 11, Society for the Study of Amphibians and Reptiles. Ithaca, New York.
- Wilkinson J.W. (1994) An account of successful captive reproduction of Bombina bombina, the European fire-bellied toad. British Herpetological Society Bulletin, 35, 12-16
- Burton M.S., Thorne E.T., Anderson A. & Kwiatkowski D.R. (1995) Captive management of the endangered Wyoming toad at the Cheyenne Mountain Zoo. Bulletin of the Association of Reptilian and Amphibian Veterinarians, 5, 6-8
- Kinne O., Kunert J. & Zimmermann W. (2004) Breeding, rearing and raising the red-bellied toad Bombina bombina in the laboratory. Endangered Species Research, 1, 11-23
- Lee S., Zippel K.C., Ramos L. & Searle J. (2006) Captive breeding program for the Kihansi spray toad (Nectophrynoides asperginis) at the Wildlife Conservation Society, Bronx, New York. International Zoo Yearbook, 40, 241-253
- Martín-Beyer B., Fernández-Beaskoetxea S., Garcia G. & Bosch J. (2011) Re-introduction program for the common midwife toad and Iberian frog in the Natural Park of Peñalara in Madrid, Spain: can we defeat chytridiomycosis and trout introductions? Pages 81-84 in: Global Re-introduction Perspectives: 2011. More case studies from around the globe. IUCN/SSC Re-introduction Specialist Group & Abu Dhabi Environment Agency, Gland, Switzerland.
- Canessa S. (2012) Trying to reverse the decline of the Apennine yellow-bellied toad in northern Italy. Froglog, 101, 24-25