Baw Baw Frog
(Philoria frosti)
The Baw Baw frog is only found in sub-alpine wet heathland and in gullies within montane vegetation at high altitudes on the Baw Baw Plateau. It breeds between September and December, when males may be heard calling for mates around special breeding sites. Females possess specially modified fingers, which they use to whip the mucous that surrounds their eggs into a protective foam nest. Adult frogs remain inactive during the cold months before the breeding season, sheltering in refuges. Numbers of individuals have drastically declined from over 10,000 in the 1980s to just 250 individuals in the 2000s. The cause of this decline is enigmatic, although possibilities include climate change and diseases, such as chytridiomycosis.
Urgent Conservation Actions
A Recovery Pan was developed for this species in 1997 and all of the actions featured here should be continued.
The Baw Baw Plateau, in Victoria, southeastern Australia.
Evolutionary Distinctiveness
Order: Anura
Family: Limnodynastidae
The Baw Baw frog is a member of a relatively small and diverse family of frogs called the Limnodynastidae. This group is found in Australia, Tasmania and New Guinea, and was formally classified as a subfamily of the Myobatrachidae, or “Australian froglets”. However, further investigation revealed that the Limnodynastidae were a family in their own right comprising 44 species. This lineage diverged from their closest relatives in the Australian froglets family about 90 million years ago in the late Cretaceous. This was 25 millions years before the extinction of the dinosaurs and makes the Limnodynastidae as distinct from their closest relatives in terms of evolutionary time as bats are from zebras.

Until recently, the Baw Baw frog was the lone member of its genus Philoria, which was named the “Baw Baw frogs” eponymously after its one constituent species. However, a recent reorganisation of the Australian frog species into a new taxonomy has combined Philoria with a second genus Kyarranus, the “sphagnum frogs”. The Baw Baw frog is therefore now grouped with five other species, although it remains a highly evolutionarily distinct amphibian. An interest feature of this species is that female Baw Baw frogs possess specially modified hands, with flanged first and second fingers, which they use to whip the musous that surrounds their eggs into a protective foam nest in which the eggs develop.
The Baw Baw frog is a medium-sized species, with females measuring around 51.6 mm in total length, and males being smaller at 44.5 mm. Males and females may also be differentiated by the male’s longer legs and wider head, and female’s flanged inner first and second finger. The fingers and toes are unwebbed. The surface of the skin is scattered with small warts, particularly on the sides and rump, giving a 'prickly' appearance. The dorsal or upper surface of the adults is predominantly brown to dark brown with cream-yellow flecks or spots, and/or larger patches spreading from the top of the head and snout to the back. A characteristic brown-black lobe-shaped gland (called the paratoid gland) occurs behind each eye, extending back over each shoulder. The ventral or lower surface of the body is smooth, ranging in colour from cream to dark yellow, and heavily pigmented with brown flecking. The throats of the males are dark brown-black.

Metamorphing young and juveniles look somewhat different from adults. Their colour varies from cream to brown with dark brown irregular flecks and patches. A dark brown band occurs from the snout, through the eye, to the base of the forelimb. Young Baw Baw Frogs have been described as looking strikingly similar to the other members of genus, which were formally in the sphagnum frogs genus Kyarranus and occur in northern New South Wales.
The breeding season of the Baw Baw frog is between September-December, which is when the males are calling for mates. Egg laying appears to be confined to a shorter interval of 2-3 weeks during this period, when a peak in calling activity occurs, although the timing of this peak in calling activity may vary between breeding seasons. Calling may be heard at any time of the day or night, with the greatest levels of activity being recorded during relatively warm, humid conditions. Very little calling activity occurs at temperatures near freezing or when temperatures are high with low humidity.

Egg masses are deposited in a transparent foam nest (which measures about 80 mm across and 30-40 mm in height) at the calling site, or nearby, during mating. The males clasp the females from behind around the waist, in a behaviour termed “inguinal amplexus”. The foam nest is produced by the female beating air bubbles into the mucous and eggs with her distinctive flanged fingers during egg laying. The egg mass may be deposited at varying depths in vegetation, or below the surface of the ground, depending on the site. Foam nests have been found at depths of over a metre, whilst others are deposited in vegetation very close to the surface.

Clutch sizes reported in the literature range from 50-185 eggs, which are white and unpigmented, measuring about 4 mm in diameter. More than one clutch of eggs may be laid at a single site, and it is also possible that females deposit a portion of their eggs at more than one site. Under natural conditions the embryonic period varies from 5-8 weeks, with non-feeding tadpoles hatching with a residual yolk mass that maintains them through to metamorphosis. The tadpoles usually remain at egg-laying sites until they develop into feeding froglets. However, upon hatching the tadpoles have also been observed to move small distances in shallow water from the nest site, remaining under cover of vegetation and/or woody debris, and occasionally they are washed into nearby pools.

Several Baw Baw frogs have previously been radio-tracked in a study conducted by Gregory J.Hollis over 6 months in the mid-1990s. The finding of this study were that movements of the adults are variable and restricted to particular weather patterns. During the breeding season, some males remain at calling sites for most of the season, whilst others move away after several weeks. Contrastingly, studies by B.S. Malone in the 1980s, when the Baw Baw frog was relatively common, found that calling males continually disappeared from calling sites throughout the breeding season, only to be replaced by others. Radio-tracking and trapping studies indicate that females move into breeding sites from adjacent habitats to lay their eggs, then return to those same adjacent habitats.

At the end of the breeding season the movement of the males varies, with some individuals remaining in close proximity to the breeding sites (within 6 m), and others moving considerable distances (up to 82 m away). Similarly, radio-tracking showed that some females also move relatively short distances from breeding sites (less than 8 m), whilst others moved up to 40 m away. Egg-bearing females have been encountered in sub-alpine woodland habitats up to 70 m from known male calling sites early in the breeding season. It is not known whether Baw Baw frogs move during the cold months of the year when snow lies on the ground (June-September), although it is presumed that they remain relatively inactive, sheltering under logs or in burrows. Baw Baw frogs consume a variety of invertebrates (both ground- and water-dwelling species), including a high percentage of earthworms.
The Baw Baw frog is a habitat specialist, occurring only in the western and central area of the Baw Baw plateau along seepage lines within (or at the periphery of) sub-alpine wet heathland and in gullies within montane vegetation. The breeding areas for this species are predominantly natural cavities in or under vegetation, logs, rocks peat and soil, or combinations of these, that act as catchments for water travelling down slopes. These sites occur along seepages or rivulets that drain water from the slopes of sub-alpine wet heathland and in gullies that drain the plateau. Historical distribution The Baw Baw frog is restricted entirely to the Baw Baw Plateau, located approximately 120 km east of Melbourne, Victoria. Despite searches of suitable habitat in close proximity to the plateau (e.g. Mount Useful and Mount Torongo), the species has never been found elsewhere. The Baw Baw frog was found to be widely distributed and abundant in the west (Mount Baw Baw), central (Mount St. Phillack) and northwaest (Mount Whitelaw) parts of the plateau. There were fewer records from the eastern region (Mount St Gwinear), and the species was conspicuously absent from the southeastern region, although at lower elevations, between 960-1,300 m, records of the species occur from montane forest along the southern escarpment of the Baw Baw Plateau.

The Baw Baw frog has now disappeared form over 80% of its former occupied range, since it is now only present in the western and central area of the Baw Baw Plateau.
Systematic surveys for calling males from 1993 to 1996 show that the distribution of the species is currently restricted to the western and central area of the Baw Baw plateau in Victoria, southeastern Australia. This distribution was also reported by B.S. Malone in the mid-1980s as the stronghold area for the Baw Baw frog. Within this new distribution, however, a number of breeding areas that previously contained up to several hundred calling males (e.g. Moondara Flat and Freeman's Flat), have not had frogs recorded in them since the 1980s. This species occupies an elevational range of 1,260-1,560 metres above sea level within the Baw Baw National Park. At lower elevations, between 960-1,300 m, records of the species occur from montane forest along the southern escarpment of the Baw Baw Plateau.
Population Estimate
In 1983 and 1984, a comprehensive assessment of the distribution of the species was undertaken by B.S. Malone. The Baw Baw frog was found to be widely distributed and abundant in the west (Mount Baw Baw), central (Mount St. Phillack) and northwaest (Mount Whitelaw) parts of the plateau. There were fewer records from the eastern region (Mount St Gwinear), and the species was conspicuously absent from the southeastern region. Over this period, adult male population on the plateau was estimated at over 10,000 individuals.

During a series of extensive annual surveys carried out since 1993, a considerable reduction in the abundance of the species was observed. Malone recorded calling males in 73% (64 out of 88) of frost hollows surveyed in 1983 and 1984, compared to 46% (22 of 48) recorded by Gregory J. Hollis from Environment Australia in the Department of Natural Resources and Environment in 1993. In a subset of 35 frost hollows surveyed in both 1983 and 1993, Malone recorded 3,694 males in 1983, whilst Hollis record only 83 just 10 yeas later. Similarly, in a subset of 19 frost hollows surveyed in both 1984 and 1993, 885 males were recorded in 1984 compared with only 19 in 1993.

By the mid- to late-1990’s, researchers were recording just over 2% of the number of males recorded by Malone in 1983-1984. Surveys during subsequent years (1994-1997) indicated that the species is currently restricted to the western half of the Baw Baw plateau (particularly to steeper montane forested areas on the edge of the western plateau), with a contraction of the distribution from eastern and western areas. Twenty-four sites surveyed on the Baw Baw plateau originally by Malone in the mid-1980s were resurveyed annually in the 1990s and all sites were found to have experienced a very large reduction in the numbers of males recorded. The average number of calling males recorded at these 24 sites declined from 124 individuals in 1983 to 1.5-3.3 individuals over the five year period 1993-1997. In 1983-1984 the maximum population size recorded at a monitoring site was 667 individuals, which decreased dramatically to a high of 41 individuals by 1993-1997. Currently, the population size is estimated to be less than 250 adults, down from over 10,000 in 1983-1984. There has clearly been a precipitous and severe decline of this species over the past 20 years.
Population Trend
The Baw Baw frog is registered as in decline in the ICUN Red List of Threatened Species.
The Baw Baw frog is listed as Critically Endangered in the IUCN Red List of Threatened Species because of a drastic population decline, estimated to be more than 80% over the last three generations, inferred from the apparent disappearance of most of the population; and because its extent of occurrence is less than 100 km sq., and its area of occupancy is less than 10 km sq., its distribution is severely fragmented, and there is continuing decline in the extent and quality of its habitat, area of occupancy, number of subpopulations, and number of mature individuals; and because its population size is estimated to number fewer than 250 mature individuals, with no subpopulation greater than 50 individuals, and it is experiencing a continuing decline.
The swift decline of the Baw Baw frog coincides with a recent global phenomenon of declining amphibians, with populations disappearing from many parts of the world, even in areas of seemingly good habitat. There have been many reported declines of species restricted to mountain-top and alpine environments, both in Australia and the rest of the world. This is relevant to the conservation of the Baw Baw frog because it occurs at high altitudes, up to about 1,560 metres above sea level in parts of the Baw Baw National Park, and is a habitat specialist within sub-alpine wet heathland and montane vegetation. Although the exact cause of this decline is currently somewhat of a mystery, there are several potential causes, and few have been investigated thoroughly. These include climate change; ultraviolet radiation; atmospheric pollution; and pathogens, such as the virulent fungal disease chytridiomycosis that is having a massive impact upon many Australian amphibian populations, possibly driving some species to extinction. A thorough investigation of these hypotheses has yet to be undertaken for the Baw Baw frog, or for any other Australian "mountain-top" species. Forestry operations may also represent a threat to the species where it occurs in State Forest. Invasive species such as willow (Salix cinerea), cattle, rabbits, Sambar deer, foxes, dogs and cats have also been identified as potentially having negative consequences for the Baw Baw frog.

The dearth of information available on the population dynamics and structure of the Baw Baw frog is currently making it very difficult to interpret the observed decline in the adult male population.
Conservation Underway
The species' habitat is protected within Baw Baw National Park, which covers an area of approximately 80 km sq. of the Baw Baw Plateau, at an altitude of between 1260-1560 metres. However, around 3.5 km sq. near Mount Baw Baw is managed by the Victorian Alpine Resorts Commission. The Baw Baw frog is listed as endangered in Australian legislation, and research and monitoring are currently in place for this species.
Conservation Proposed
Although a number of conservation actions are already underway for the Baw Baw frog, a Recovery Plan for 1997-2001, prepared by Gregory J. Hollis of Environment Australia’s Endangered Species Program, part of the Department of Natural Resources and Environment, proposed various conservation actions necessary for the conservation of the Baw Baw frog. These included continued monitoring of wild populations across the species’ range; identification of factors responsible for the decline in the species, and of the relative contribution of various environmental and human-cause anthropogenic threats, including climate patterns, UV radiation, predators, human distubance, and disease; the development of methods to be employed in a captive breeding initiative for the Baw Baw frog; the implementation of a management strategy to protect and maintain the species’ habitat, including community information brochures and interpretation signs, campfire prohibition, cattle eradicated from the plateau, control of willow growth, weed control, and the maintenance of walkways and relocation of tracks away from sensitive areas; and the coordination and supervision of research and management actions.

The only conservation measures that may be proposed for the Baw Baw frog is that the actions outlined in the Recovery Plan continue, and especially that habitat protection and research into the cause of the Baw Baw frog’s alarming decline be prioritised. Plans for a capitive breeding initiative should also be followed through to breed a captive reserve population of this species that may ensure against extinction of the species should the wild populations be lost before all threats can be mitigated.
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