Patterns of habitat-use are used widely as management guides in the conservation of wildlife. However, even for relatively well-studied species, such the Green and Golden Bell Frog Litoria aurea, our knowledge of specific habitat requirements is lacking.
This study sought to compare the patterns of breeding habitat shown by L. aurea in New South Wales (NSW), Victoria and New Zealand (where it is a feral species), with those described in an earlier study of Pyke and White (1996), to review the conservation status of this species in Victoria,and to relate its observed patterns of distribution and habitat-use to the distribution of the introduced Plague Minnow (Gambusia holbrooki in Australia; G. affinis in New Zealand).
We found that L. aurea used similar breeding habitats in NSW,Victoria and New Zealand.Across these areas its breeding is almost completely restricted to water bodies that are still, relatively unshaded, and low in salinity (i.e., <7.3 ppt). All of its known breeding sites are highly disturbed,mostly through human activities but also through flooding and other natural processes. It generally breeds in small (i.e., <1000 sq m), shallow (i.e., <1 m) ponds that are either ephemeral or fluctuate significantly in water level, are free of Gambusia and other predatory fish, and have emergent aquatic vegetation. Its breeding habitat also usually has potential shelter provided by nearby rocks or thick, low vegetation.
Yet L. aurea is adaptable to different habitats and we found it breeding in a wide range of conditions including ponds lacking emergent vegetation and those already colonised by Gambusia. Breeding ponds ranged in terms of substrate, nearby terrestrial vegetation, water source, and water properties including turbidity, dissolved oxygen, oxidation reduction potential, pH and temperature.
Gambusia may have had a negative impact on the distribution of L. aurea in New Zealand and could threaten populations in Victoria.We failed to find L.aurea at sites in New Zealand where it had previously been reported but that are now colonised by Gambusia. This fish has not invaded L. aurea habitat in Victoria, but it can potentially do so from nearby regions. Further surveys for L. aurea in Victoria and New Zealand seem warranted.
Paradoxically New Zealand may offer unique opportunities for further research on the biology of Australian frogs. The commonly encountered frogs in New Zealand are three Australian species, two of which (i.e., L. aurea and L. raniformis) are considered threatened with extinction in Australia. It may be possible in New Zealand to study relatively large populations of these Australian frog species, in relatively simple frog communities and habitats. Because these species are not protected in New Zealand, field studies can also incorporate experimental manipulations not readily possible in Australia.