Distribution and Habitat
Population and Distribution
Philoria frosti is restricted entirely to the Baw Baw Plateau, located approximately 120 km e. of Melbourne, Vic. (Malone 1985a; Hollis 1995). Despite searches in close proximity to the plateau, and in similar environments (e.g. Mt Useful, Mt Torongo), the species has not been found elsewhere (Malone 1985a). Encompassing an area of approximately 80 km2, the Baw Baw Plateau between approximately 1260-1560 m is contained within the Baw Baw NP, except for approximately 3.5 km2 near Mt Baw Baw that is managed by the Victorian Alpine Resorts Commission (Hollis 1997). At lower elevations, between 960 and 1300 m, records of the species occur from montane forest along the s. esarpment of the Baw Baw Plateau (G. Hollis pers. comm.). In 1983 and 1984, Malone (1985a) undertook a comprehensive assessment of the distribution of the species. Philoria frosti was found to be widely distributed and abundant in the w. (Mt Baw Baw), central (Mt St Phillack) and n.w. (Mt Whitelaw) parts of the plateau. There were fewer records from the e. region (Mt St Gwinear), and the species was conspicuously absent from the s.e. region. Malone (1985a) estimated the adult male population on the plateau to be over ten thousand individuals.
During a series of extensive annual surveys carried out since 1993, a considerable reduction in the abundance of the species has been observed (Hollis 1995, 1997; Osborne et al. 1999). Malone (1985a) recorded calling males in 73% (64 of 88) of frost hollows surveyed in 1983 and 1984, compared to 46% (22 of 48) recorded by Hollis (1995) in 1993. In a subset of 35 frost hollows surveyed in both 1983 and 1993, Malone (1985a) recorded 3694 males compared with 83 by Hollis (1995). Similarly, in a subset of 19 frost hollows surveyed in both 1984 and 1993, 885 males were recorded in 1984 compared with 19 in 1993. Hollis (1995) and Osborne et al. (1999) only recorded 2.2% and 2.1% of the number of males recorded by Malone in 1983 and 1984 respectively. Surveys during subsequent years (1994-1997) indicated that the species is currently restricted to the w. half of the Baw Baw plateau (particularly to steeper montane forested areas on the edge of the w. plateau W. Osborne pers. comm.), with a contraction of the distribution from e. and w. areas (Osborne et al. 1999). Twenty-four sites surveyed on the Baw Baw plateau originally by Malone (1985a) were re-surveyed annually by Osborne et al. (1999) for numbers of calling males present. At all sites there has been a very large reduction in the numbers recorded. The mean number of calling males recorded at 24 sites declined from 124 individuals in 1983 to between 1.5 and 3.3 individuals over the five years 1993 to 1997. In 1983-1984 the maximum population size recorded at a monitoring site was 667 individuals, by contrast between 1993 and 1997 the largest population recorded was 41 individuals. In 1997 frogs were recorded at only six of the 25 monitoring sites.
Philoria frosti has only been recorded from Baw Baw NP, Mt Baw Baw Alpine Resort and adjoining SF (Hollis 1997).
Philoria frosti is a habitat specialist. During the breeding season (Sep.-Dec.), calling males, gravid females and egg masses have been recorded, along seepage lines within or at the periphery of sub-alpine wet heathland and in gullies within montane vegetation communities (Malone 1985a; Hollis 1995). Overall, surveys from 1993-1996 indicate that breeding localities are restricted to topographically protected gully habitats compared with the broader breeding distribution of the species over a decade ago (Hollis 1997). The breeding microhabitat of the species is predominantly natural cavities in or under vegetation, logs, peat and soil, and rock (or combinations of these), that act as catchments for water travelling down slope (Littlejohn 1963; Malone 1985a; Hollis 1995). 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. Larvae usually remain at oviposition sites through to metamorphosis (Barker et al. 1995; Hollis 1997). Upon hatching, however, larvae have also been observed to move small distances in shallow water from oviposition sites, while remaining covered under vegetation and/or woody debris (Hollis 1997) or to be washed into nearby pools (B. Malone pers. comm. in Hollis 1997).
Life History, Abundance, Activity, and Special Behaviors
Calling activity has been recorded in early Sep., continuing as late as the last week in Dec. (Malone 1985a; Hollis 1995; Hollis. Pers. comm.). Oviposition (egg laying) appears to be confined to a shorter interval of 2-3 weeks during this period, when a peak in calling activity occurs (Malone 1985a, b; Hollis 1995). The timing of this peak in calling activity may vary between breeding seasons (Hollis 1997). Calling activity may occur at any time of the day or night, with the greatest levels of activity being recorded during relatively warm, humid conditions (Hollis 1997). Very little calling activity occurs at temperatures near freezing (Malone 1985a) or when temperatures are high with low humidity (Hollis 1997).
Egg masses are deposited in a transparent foam nest (8 cm diameter and 3-4 cm high) at the calling site, or nearby, during inguinal amplexus (Littlejohn 1963). The foam nest is produced by the female beating air bubbles into the mucous and eggs with flanged fingers during egg laying (Littlejohn 1963). The egg mass may be deposited at varying depths in vegetation, or below the ground surface, depending on the structural attributes of the site (Hollis 1997). Depths of over a metre have been observed, whilst others are deposited in vegetation very close to the surface (Hollis 1997). Clutch sizes reported in the literature range from 50-185 (see Littlejohn 1963; Malone 1985a, b; Tyler 1992). Ova are white and unpigmented and measure on average 4 mm in diameter (Malone 1985b). Oviposition of more than one clutch may occur at a single site (Malone 1985b; Hollis 1997). It is also possible that females deposit a portion of their eggs at more than one site (Malone 1985a). Under natural conditions the embryonic period varies from 5-8 weeks, with individuals hatching at Gosner stages 22-23 (Malone 1985a, b). The larvae are non-feeding, hatching with a residual yolk mass that maintains them through to metamorphosis (Malone 1985a, b).
Examination of the stomach contents of 30 museum species shows that P. frosti consumes a variety of invertebrates (8 orders of aquatic and terrestrial species) including aquatic larvae and an unusually high percentage of annelids (G. Hollis pers. comm.).
Willow (Salix cinerea), cattle, rabbits, Sambar deer, foxes, dogs and cats have been identified as invasive species (G. Hollis pers. comm.).
A radio-tracking study conducted over 6 months (Nov. 1995-Apr. 1996) showed that movement by adults is variable and restricted to particular weather patterns (Hollis 1997). During the breeding season, some males remain at calling sites for most of the season, whilst others move away after several weeks (Hollis 1997). By contrast, Malone (1985a, b) found that in the 1983 and 1984 surveys, when P. frosti was relatively common, 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 the same adjacent habitats (Hollis 1997). Movement by males at the completion of the breeding season varies, with some individuals remaining in close proximity to the breeding sites (<6 m), whilst others moved considerable distances (up to 82 m linear distance) (Hollis 1997; G. Hollis pers. comm.). Similarly, radio-tracking showed that some females also move relatively short distances from breeding sites (<8 m), whilst others move considerable distances away (up to 40 m) (Hollis 1997). Gravid females have been pit-trapped in sub-alpine woodland habitats up to 70 m from known male calling sites early in the breeding season, and spent females at similar distances in the same habitat at the end of the breeding season (Hollis 1997). It is not known whether frogs move during the cold months of the year when snow lies on the ground (Jun.- Sep.), although it is presumed that they remain relatively inactive like other ectotherms in temperate regions (Hollis 1997).
Life History, Abundance, Activity, and Special Behaviors
The following information is taken from Hollis (1997)
The dearth of information available on the population dynamics and demography of the Baw Baw Frog makes it is very difficult to interpret the observed decline in the adult male population. This decline however, coincides with a recent global phenomenon of declining amphibians (e.g. Barinaga 1990; Blaustein and Wake 1990; Tyler 1991), and perhaps of more concern, with the reported decline of species restricted to mountain-top and alpine environments in Australia (e.g. Osborne 1990; Richards et al. 1993) and overseas (La Marca and Reinthaler 1991; Crump et al. 1992). Numerous hypotheses have been generated to explain these declines, but few as yet have been investigated thoroughly. Those that have, or are currently being investigated, include climate (Osborne 1990; Richards et al. 1993), ultraviolet radiation (Blaustein et al. 1994), atmospheric pollution (Bradford et al. 1994) and pathogens (Blaustein et al. 1994;Trenerry et al. 1994). No thorough investigation of these hypotheses has been 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 SF (W. Osborne pers. comm.).
Philoria is a genus of frogs native to eastern and southern Australia. These frogs are all confined to mountain areas, with 5 species occurring in the mountains of northern New South Wales and southern Queensland. One species occurs in Victoria. All species are listed as endangered, except the Baw Baw frog, which is listed as critically endangered. They are small to medium sized frogs that live in water saturated sites, such as sphagnum bogs and seepages on rocky slopes. The eggs are laid in foam nests hidden from light. The tadpoles remain within the nest and live entirely on the yolk.
Some taxonomists class only the Baw Baw frog (Philoria frosti) in the genus Philoria and class the other 5 species in the genus Kyarranus because of osteological features, size differences (Philoria frosti is larger) and the presence of a large gland behind each eye (parotoid gland).
There are six species in the genus Philoria:
|Common name||Binomial name|
|Baw Baw frog||Philoria frosti Spencer, 1901|
|Mountain frog||Philoria kundagungan (Ingram & Corben, 1975)|
|Loveridge's frog||Philoria loveridgei Parker, 1940|
|Southern mountain frog||Philoria pughi Knowles, Mahony, Armstrong & Donnellan, 2004|
|Richmond Range mountain frog||Philoria richmondensis Knowles, Mahony, Armstrong & Donnellan, 2004|
|Sphagnum frog||Philoria sphagnicolus (Moore, 1958)|
- Frost, Darrel R. (2013). "Philoria Spencer, 1901". Amphibian Species of the World 5.6, an Online Reference. American Museum of Natural History. Retrieved 18 December 2013.
- IUCN (2013). "IUCN Red List of Threatened Species. Version 2013.1. <www.iucnredlist.org>". Retrieved 18 December 2013.
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