Australia has one of the most diverse frog assemblages in the world with 216 species, 93% of which are endemic. Over the past 30 years, dramatic declines in frog numbers have been reported around the world including in Australia. Four Australian frog species have become extinct and another 15 species are currently endangered.
The main threats to Australian frogs include habitat destruction/degradation, herbicides and pesticides used in agricultural and horticultural areas, introduced predatory aquatic species (e.g. mosquito fish, trout) and the amphibian chytrid fungus.
In many frog species, chytrid fungus causes the disease, chytridiomycosis, which has been linked to severe population declines and extinctions of amphibian species around the world. Chytrid fungus is present in the south-west of Western Australia and the Kimberley region in the north of the State.
Three frog species endemic to Western Australia are listed as threatened by the IUCN:
- the White-bellied Frog (Geocrinia alba) is Critically Endangered
- the Orange-bellied Frog (Geocrinia vitellina) is Vulnerable
- the Sunset Frog (Spicospina flammocaerulea) is Vulnerable
As part of conservation efforts for these threatened native frog species, a breeding and research program was established at Perth Zoo.
This program began in 2005 with a focus on research to underpin the development of successful rearing, breeding and management techniques for frogs and the establishment of insurance populations of selected Western Australian species.
Perth Zoo initially investigated the reproductive biology and husbandry requirements of several non-threatened Western Australian frog species. These included the Roseate Frog (Geocrinia rosea) and two species from the Kimberley region (Notaden weigli and Litoria cavernicola).
Both the Roseate Frog and Cave-dwelling Frog (Litoria cavernicola) bred successfully. This allowed staff to gain valuable experience keeping, breeding and rearing frogs. The Roseate Frog is closely related to the two threatened Geocrinia species, so it gave staff a good basis when the focus of the program shifted to the threatened species.
The White-bellied and Orange-bellied Frogs are currently the focus of head-starting (protected rearing at the Zoo) and breed-for-release programs at Perth Zoo. In the wild, Geocrinia egg nests experience high mortality, largely due to predation. The head-starting program involves collecting egg nests in the wild and bringing them back to Perth Zoo where they are reared in a predator-free environment to increase their chance of reaching adulthood.
Since 2008, Perth Zoo has successfully reared White-bellied Frogs from egg nests collected from the wild. In September 2010, 63 of these frogs were released into suitable habitat near Witchcliffe, in Western Australia’s south-west, in an effort to re-establish this critically endangered species in an area where they have become locally extinct. Between 2011 and 2013, a further 138 captive-reared and five Zoo-born White-bellied Frogs were released into the wild.
In 2011, Perth Zoo successfully bred White-bellied Frogs and Sunset Frogs – a world first for both species.
In 2011, seven Orange-bellied Frogs were successfully reared from egg clutches collected from the wild and released. While this species is closely related to the White-bellied Frog, it is proving more difficult to rear and breed. Twenty Orange-bellied Frogs raised from egg nests collected from the wild were released in 2012 and a further 65 in 2013.
In December 2011, 30 Sunset Frogs and 251 Sunset tadpoles were released at a swamp near Walpole in the south-west of Western Australia. Most of the adult frogs were reared at Perth Zoo and all the tadpoles were bred at Perth Zoo. With only 30 known populations of the Sunset Frog in a tiny corner of the south-west, it is hoped the zoo-bred amphibians will successfully establish a new population outside the known distribution area of this species.
Partners and Supporters
The frog breeding and rearing program is run by Perth Zoo in partnership with the Western Australian Department of Environment and Conservation (DEC), Western Australian Museum and University of Western Australia. The original research phase was funded through a grant from the Western Australian Office of Science and Innovation. The breeding and rearing program has been partly funded by DEC and the South West Catchments Council as well as small grants from Perth Zoo’s Wildlife Conservation Action fundraising program and the Zoo and Aquarium Association.