Western Australia has had state legislation protecting frogs since 1958. The Western Australian Wildlife Conservation Act also lists on Schedule 1 "species that are likely to become extinct or is rare or otherwise in need of special protection" - the endangered species.
Three frogs have been, or are currently listed on Schedule 1: the sandhill frog, Arenophryne rotunda, the white and orange-bellied frogs, Geocrinia alba and G. vitellina along with two other species, the spotted burrowing frog, Heleioporus albopunctatus and a new, undescribed, genus from the south coast.
Unlike eastern Australia few frog species in south-western Australia seem to be in decline, and, for those that are, there are identifiable threats.
Arenophryne rotunda:
This species is no longer listed as endangered. It was initially given this status because it was known from a single locality and only a few specimens had been collected. It was the first frog given this status in W.A.
A. rotunda is a small frog, that has been extensively studied on coastal sand dune systems on the western side of Shark Bay. Frogs walk across the dune surface leaving distinctive tracks. They feed largely on ants. Breeding biology is complex. Males call in spring (August - November) with most records after rain. Pairs form then but egg deposition is delayed until the following April. Eggs undergo direct development at up to 80 cm below the sand surface and hatch about May coinciding with opening winter rains.
Field work starting in 1979 and particularly in 1980 established that this species was one of the most abundant frogs in Australia and has population densities equivalent to those of the most abundant terrestrial salamanders in North America. It is no longer listed as endangered.
Geocrinia alba and G. vitellina:
The white and orange bellied frogs, Geocrinia alba and vitellina, are currently under intensive study by the Geocrinia Recovery Team funded by the Australian Nature Conservation Agency's Endangered Species Program.
The orange bellied frog has a very restricted distribution, about 6 square km, all in state forest. The one identifiable threat to persistence of these populations is feral pigs. There are monitoring and hunting programs in place to deal with that threat.
The white bellied frog has a much larger range, about 100 square km, but 70% of creeks it is likely to have inhabited have been cleared. The species does not survive the loss of creek zone vegetation, particularly the understorey species. Of the remaining sites where it still occurs most are privately owned and subject to either clearing or degradation by stock grazing. The Recovery Team has a fencing program in place to protect privately owned, uncleared swamps. This program has been very successful with fencing in place or planned for several properties across the range of this species.
Heleioporus albopunctatus and salinity in the W.A. wheatbelt:
The wheatbelt of Western Australia has been extensively cleared for wheat production. Associated with this clearing there has been a rise in water tables and increases in soil salinity and runoff of salt into drainage systems. Many of the freshwater sites historically used for breeding by frogs have become too salty for eggs or tadpoles to survive.
The impact of salinity has been analysed for one species, the spotted burrowing frog, Heleioporus albopunctatus. Indications are that this species may show a decline correlated with increasing salt impacts on farming land. The data are not strong but are a warning that these impacts should be considered seriously. H. albopunctatus is still widespread in the central wheatbelt but these may all be old, mature frogs. There may be little or no current recruitment. We do not know exactly what is going on. This species deserves more study particularly by looking at the age structure of existing populations, e.g. by looking at growth rings in toe bones. H. albopunctatus has adopted novel breeding sites, formed by roadworks or salt interceptor banks and this may partly compensate for the loss of traditional breeding sites.
If salt is affecting H. albopunctatus we need to also look carefully at the other frog species known from the wheatbelt (another seven species are widespread in the region) as they may be equally affected.
The Mountain frog:
This is a new genus, discovered in 1994 and known from only three sites, north-east of Walpole on the south coast of W.A. The known range is about 6 square kilometres. It has a very distinctive appearance and colouration (orange and blue on the ventral surface) suggesting it has a very restricted distribution. This species has a conventional breeding system. Males call from shallow ponds and seepages in peaty swamps. Eggs are deposited in water. Breeding activity has only been observed after a moderate intensity fire went through the main swamp in late November 1994. There is no reason to suggest fire is a stimulus to breeding but the loss of vegetation may have raised water tables sufficiently to induce water flow from seepage systems in a dry season where otherwise there might not have been any breeding. Adult frogs survived the fire in large numbers but their survival over summer is unknown.
Threats to survival of this species include fire which may burn out large areas of peat, pigs, which may root up holes in the peat and destroy both breeding sites and refuge areas, and, plant diseases such as dieback which could destroy vegetation cover and radically alter the hydrology of the swamp systems. By chance, all known sites occur in national parks. Western Australia has not suffered the radical declines observed for several frog species in eastern and south-eastern Australia. Species in decline or at risk have identifiable threats and action is being taken to deal with these. Because the West Australian frog fauna has been exposed to many of the threats suggested as causes of frog declines in eastern Australia W.A. frogs may present an opportunity for comparative studies on causes of decline elsewhere in Australia.
Taken from the newsletter of the ACT Herpetological Association. For further information contact:
J.D. ROBERTS, Department of Zoology, University of Western Australia, Nedlands, W.A. 6907.