Baw Baw Frog
Distribution and Habitat
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).
Life History, Abundance, Activity, and Special Behaviors
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).
Trends and Threats
Forestry operations may also represent a threat to the species where it occurs in SF (W. Osborne pers. comm.).
Barinaga, P.H. 1990. Where have all the froggies gone? Science 247: 1033-1034. Blaustein, A.R. & D.B. Wake 1990. Declining amphibian populations: a global phenomenon? Trends in Ecology and Evolution 5: 203-204. [Journal; Status=Final; Refereed=Yes]
Blaustein, A.R., P.D. Hoffman, D.G. Hokit, J.M. Kiesecker, S.C. Walls & J.B. Hays 1994. UV repair and resistance to solar UV-B in amphibian eggs: A link to population declines? Proceedings of the National Academy of Science USA 91: 1791-1795. [Proceedings; Status=Final; Refereed=Yes]
Crump, M.L., F.R. Hensley & Clark, K.L. 1992. Apparent decline of the golden toad: Underground or extinct? Copeia 1992: 413-420. [Journal; Status=Final; Refereed=Yes]
Hollis, G.J. 1995. Reassessment of the distribution, abundance and habitat of the Baw Baw Frog Philoria frosti Spencer: Preliminary Findings. Victorian Naturalist 112 (5): 190-201. [Journal; Status=Final; Refereed=Yes]
Hollis, G.J. 1997. Recovery Plan for the Baw Baw Frog (Philoria frosti). Unpublished report to Endangered Species Program, Environment Australia, Canberra. [State Recovery Plan; Status=Final; Refereed=Yes]
La Marca, E. & H.P. Reinthaler 1991. Population changes in Atelopus species of the Cordeillera de Merida, Venezuela. Herpetological Review 22: 125-128. [Journal; Status=Final; Refereed=Yes]
Littlejohn, M.J. 1963. The Breeding Biology of the Baw Baw Frog. Proceedings of the Linnean Society of New South Wales 88: 273-276. [Proceedings; Status=Final; Refereed=Yes]
Malone, B.S. 1985a. Status, distribution and ecology of the Baw Baw Frog (Philoria frosti). Arthur Rylah Institute Technical Report No. 36. Arthur Rylah Institute, Department of Conservation, Forests and Lands, Victoria. [Report; Status=Final; Refereed=Yes]
Malone, B.S. 1985b. Mortality during the early life history stages of the Baw Baw Frog (Philoria frosti). In: Biology of Australasian Frogs and Reptiles. G. Grigg, R. Shine & H. Ehmann (eds) pp. 1-5. Surrey Beatty and Sons, Sydney. [Book; Status=Final; Refereed=?]
Osborne, W.S. 1990. Declining frog populations and extinctions in the Canberra region. Bogong 11: 4-7. [Journal; Status=Final; Refereed=No]
Osborne, W., D. Hunter & G. Hollis 1999. Population declines and range contraction in Australian alpine frogs. In: Declines and Disappearances of Australian Frogs. A. Campbell (ed) pp. 145-157. Environment Australia, Canberra. [Book; Status=Final; Refereed=Yes]
Richards, S.J., K.R. McDonald & R.A. Alford 1993. Declines in populations of Australia's endemic tropical rainforest frogs. Pacific Conservation Biology 1: 66-77. [Journal; Status=Final; Refereed=Yes]
Trenerry, M.P., W.F. Laurance & K.R. McDonald 1994. Further evidence for the precipitous decline of endemic rainforest frogs in tropical Australia. Pacific Conservation Biology 1: 150-153. [Journal; Status=Final; Refereed=Yes]
Tyler, M.J. 1992. Encyclopedia of Australian Animals: Frogs. Angus and Robertson, Sydney. [Book; Status=Final; Refereed=?]
Tyler, M.J. 1991. Declining amphibians - a global phenomenon? An Australian perspective. Alytes 9: 43-45. [Journal; Status=Final; Refereed=?]
J-M. Hero; L. Shoo; C. Morrison; M. Stoneham; G. Hollis; W. Osborne; B. Malone
Written by J.-M. Hero; G. Hollis; W. Osborne; B. Malone; L. Shoo; C. Mo (m.hero AT mailbox.gu.edu.au), Griffith University
First submitted 2002-04-05
Edited by Ambika Sopory, Jean-Marc Hero (2002-05-04)
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