Action: Amphibians: Provide multiple egg laying sites within an enclosure
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- One replicated study in Australia found that frogs only bred once moved into an indoor enclosure which had various types of organic substrate, allowed temporary flooding, and enabled sex ratios to be manipulated along with playing recorded mating calls.
- One small, replicated, before-and-after study in Fiji found that adding rotting logs and hollow bamboo pipes to an enclosure, as well as a variety of substrates, promoted egg laying in frogs.
A choice of egg laying sites may be offered which vary in humidity, temperature, water level or protection from predation. This can often be done by using inexpensive, readily accessible natural items. Mimicking an amphibian’s natural environment in captivity, to meet species specific needs, could help improve breeding success.
Supporting evidence from individual studies
A replicated, before-and-after study in 1994–1996 of roseate frogs Geocrinia rosea at Melbourne Zoo, Australia found that frogs only bred after being moved to an indoor enclosure which had a mix of organic substrates with moss, mud, bark and palm peat; temporary flooding of enclosures; manipulated sex ratios; introduced females carrying eggs to males; and played recorded mating calls. The only fertile spawning occurred in spring 1996, in a well-established burrow hidden beneath dry leaf litter and eucalyptus bark which contained 25 eggs, but they were later destroyed by fungus. From 1994-1995, two male and three sub-adult frogs were housed in two outdoor tanks (120 x 60 x 60 cm) with a sub-surface water depth 50-100 mm. Males called when they were in outdoor enclosures, but fertile eggs were not produced until animals were moved to indoor tanks. From 1996, 6–7 frogs were housed in each of four indoor tanks (47 x 55 x 36 cm and 180 x 46 x 46 cm).
A small, replicated, before-and-after study in 2004-2007 in Fiji found that the provision of egg laying sites including rotting logs and hollow bamboo stems Piper aduncum and various organic substrate in an enclosure resulted in successful breeding for two pairs of Fijian ground frogs Platymantis vitianus. A total of 39 froglets were raised after one year. Two egg clutches were found, one in a section of bamboo stem filled with damp soil substrate, and another under a moist rotting log on a mix of soil and leaf litter. A captive breeding program had been running for this species since 2004, but only one froglet was reared after three years of trying. From 2006-2007, five male and five female frogs were placed in a purpose built outdoor enclosure. Further detials in: Narayan E., Christi K. & Morley C. (2009) Captive propagation of the endangered native Fiji-an frog Platymantis vitiana: Implications for ex-situ conservation and management. Pacific Conservation Biology, 15, 47-55.
- Birkett J., Vincent M. & Banks C. (1999) Captive management and rearing of the roseate frog, Geocrinia rosea, at Melbourne Zoo. Herpetofauna, 29, 49-56
- Narayan E., Christi K. & Morley C. (2007) Improvement in ex-situ egg hatchability of Fijian ground frog Platymantis vitianus by laboratory incubation of egg masses, University of the South Pacific, Suva, Fiji. Conservation Evidence, 4, 25-27