A rare animal that becomes increasingly rare and no-one knows why

The Baw Baw Frog (Philoria frosti) is a small frog of alpine and sub-alpine regions of the Baw Baw Plateau, and wet forest gullies to the south-west, in the Victorian Central Highlands.  Unlike typical frogs, it has very little webbing on its hind feet and none on the front.  It spends most of its time in wet gullies and lays eggs in small, moist cavities it constructs from plant material, small rocks and soil.  The tadpoles do not feed, and develop into small frogs in or near the egg.  The species is classified as critically endangered in Victoria, endangered in Australia (EPBC rating), is listed under the Flora and Fauna Guarantee Act (FFG) and is classified as critically endangered under the IUCN.

Clearly with such a restricted habitat and life cycle the Baw Baw Frog is a prime candidate for a rare classification.  However, since most of the early records for the species were confined to the Baw Baw National Park and that its numbers were estimated at 10,000-15,000 in 1984, the critically endangered classification might seem extreme.  But shortly after this date the species began to decline alarmingly and no-one knew why.

In the late 1970s biologists noticed that frogs all over the world were dying from unknown causes, it became one of the great mysteries of that period and research projects were funded everywhere to find a common link.  The current thinking is that the culprit is a species of water mould (Chytridiomycete) called Batrachochytrium dendrobatidis.  Water moulds, or chytrids as they are now commonly called, are primitive fungi which reproduce by means of swimming spores (they have whip-like tails similar to sperm cells) and are known to feed by breaking down plant and animal material via the release of enzymes.  The enzymes used by Batrachochytrium break down the protein keratin which is present in the skin of most vertebrates.  The skin of frogs seems to be particularly susceptible to this enzyme and as a consequence breathing and water exchange become a major problem for the animals.  The tadpoles don't seem to be affected.

Chytrids are in wet soils and moist gullies all over the world and frogs must have come into contact with them in the past so scientists are asking why is it killing them now?   One theory is that climate change has created a microclimate that is more conducive to the growth of keratin-digesting chytrids and that this is the beginning of things to come.  Another is that Batrachochytrium is an unusually virulent fungus which has been transported world wide by humans and infected frogs (frogs are shipped everywhere for school and university dissections and medical research).  Whatever the reason it does appear that some Australian frogs are under threat from this source and the Baw Baw Frog is one of them.

Today there are virtually no Baw Baw Frogs on the Baw Baw Plateau.  It is thought that this may be due to the spread of Batrachochytrium via the Common Froglet (Crinia signifera) which is widespread on the plateau and appears to be unaffected by the fungus.  Recent surveys near the Baw Baws have found new locations for the frog in wet gullies to the south-west of the plateau, a habitat which is apparently unsuitable for Crinia.  Unfortunately all of these sites are within state forests which have been earmarked for logging so there is an urgent need for a reassessment of the land-use priorities in this area if the Baw Baw Frog is to survive.