Biodiversity

Threatened species

Recovery plan for the Baw baw frog (Philoria frosti) 1997-2001

Gregory J. Hollis
Environment Australia, October 1997

Summary

Current Species Status

Critically Endangered (NRE 1997a); Endangered (Tyler 1997); Endangered (Wildlife Act 1975); Vulnerable (Schedule 1 of Endangered Species Protection Act 1992); Vulnerable (ANZECC 1995); Threatened (Schedule 1 of Flora and Fauna Guarantee Act 1988); Threatened (SAC). The Baw Baw Frog population has declined by several orders of magnitude when compared to population size estimates recorded for the species over a decade ago. The current population size of adult males is estimated to be 1-2% of the 10,000-15,000 estimated to be on the Baw Baw Plateau in 1983 and 1984. The distribution of breeding individuals is now predominantly confined to topographically protected gully habitats at higher elevation (above 1300 m) and montane forest habitat at lower elevations (as low as 1080 m). This contrasts with the species former distribution which occurred over a much wider area on the Baw Baw Plateau in sub-alpine habitats. The Baw Baw Frog is considered to be vulnerable to extinction if the factors responsible for its decline continue to operate.

Habitat Requirements and Limiting Factors

The Baw Baw Frog is restricted to a narrow set of ecological limits and possesses an unusual life history that is exhibited by very few amphibians. Breeding and non-breeding habitats are restricted to sub-alpine and montane vegetation communities that occur at elevations between 1080 and 1560 m, encompassing a small area of 80 km2 on the Baw Baw plateau. Breeding microhabitats are confined to natural cavities in or under dense vegetation, logs, soil or rock, that act as catchments for water traveling down slope. These occur predominantly along seepage lines within or at the periphery of sub-alpine wet heathland and in gullies. Non-breeding habitat consist of those used for breeding purposes as well as habitats away from and adjacent to breeding sites, including sub-alpine woodland and montane wet forest, where frogs shelter beneath dense vegetation, roots, logs, rocks and leaf litter. The sheltering sites sought by the species are moist and cool, and buffered against external weather extremes. Movement by adults during spring, summer and autumn is restricted predominantly to periods of wet, relatively warm weather associated with the arrival of rain-bearing frontal weather patterns.

Factors that limit the Baw Baw Frog are largely unknown. Those that change or modify habitat characteristics and requirements are a potential threat to the ecology and biology of Baw Baw Frog. These include environmental factors (e.g. long and short-term climate change, increased UV radiation) and anthropogenic factors (e.g. vegetation clearing/modification; timber harvesting; predation and habitat disturbance by introduced predators; introduced plants and air/water pollution). The factors responsible for the recent decline in the Baw Baw Frog population are currently unknown.

Recovery Plan Objectives

Overall objective

To achieve down-listing of the species from endangered within 10 years based on the IUCN (1994) criteria of population size and trends, extent of occurrence, and probability of extinction.

Specific objectives

  1. to secure the species from the threat of extinction by:
    1. ensuring long-term survival of a genetically viable population across its geographic range,
    2. increasing the population to a level predicted by PVA analyses to be adequate for long-term viability.
  2. to increase the population such that the species is no longer critically endangered,
  3. to gain an understanding of those aspects of the biology and ecology of the species which will enable effective management of the population,
  4. to determine reasons for observed decline across the species geographic range,
  5. to address threatening processes and change or implement management practices where appropriate,
  6. to ensure that landuse activities will not impinge upon the survival of the species.

Recovery Criteria:

  1. secure population by:
    • monitoring population numbers and trends, distribution and habitat characteristics over 5 years using rigorous experimental design,
    • until optimal population levels are determined by PVA analyses, an interim target is to increase numbers of calling males to twice the population estimates (400-600) obtained from monitoring transects surveyed on the plateau, by 2002,
  2. knowledge of those aspects of population dynamics and demographics necessary to understand the population decline, i.e.:
    • understand extent of habitat use below 1300 m a.s.l., by end of 1998,
    • understand longevity and age structure of population, as determined by skeletochronology by end of 1998,
    • detailed knowledge of breeding habitat, by end of 1999,
    • knowledge of diet by end of 1998,
    • knowledge of movement by end of 1998,
    • knowledge of reproductive success and recruitment to post-larval stages, by end of 2000,
    • complete PVA analysis by 2002,
  3. identification of factors responsible for the decline in the species, and of the relative contribution of various environmental and anthropogenic threats, in particular:
    • knowledge of past climate patterns, by end of 1998, and of potential effects of these patterns on population levels,
    • knowledge of the extent of predation by introduced predators, by end of 1999,
    • knowledge of susceptibility of the Baw Baw Frog to UV radiation, of likely exposure levels, and of probable effects on the population, by end of 1999,
    • knowledge of extent of disturbance to habitat by various anthropogenic factors including introduced herbivores, introduced weeds, changed drainage patterns, track network, alpine village development, and recreational disturbance, by end of 1999, and of the effects of these habitat disturbances on the frog population, by 2002,
    • knowledge of any contribution of pathogens to the decline.
  4. determine husbandry methodology for larvae and metamorphlings, by end of 1998,
  5. implement a management strategy to protect and maintain the current extent and integrity of the species habitat by reducing levels of threats identified as potentially responsible for the decline, by 2002, including initially:
    • community information brochures and interpretation signs available, by end of 1998,
    • campfire prohibition (and ash removal) implemented, by 1998,
    • cattle eradicated from the plateau, by end of 2000,
    • Salix controlled, by 2002,
    • weed control from alpine village area implemented immediately, and continuing,
    • track maintenance, particularly of board-walks, and relocation of tracks away from sensitive areas immediately, and continuing,
  6. efficient and effective coordination and supervision of research and management actions.

Actions Needed

A Recovery Team, comprising representatives of NRE, Environment Australia, University of Melbourne, Latrobe University, Alpine Resorts Commission and other organisations as appropriate, will be formed (Action 3.13.1) to coordinate and supervise the following actions:

Estimated Cost of Recovery: 1997 estimates in $000s/year.
Action 1997 1998 1999 2000 2001 Total
(3.1) 67.25 14.75 14.75 14.75 14.75 126.25
(3.2) 41.0 0 0 0 0 41.0
(3.3) 7.0 0 0 0 0 7.0
(3.4) 8.0 0 0 0 0 8.0
(3.5) 12.3 7.0 10.0 0 0 29.3
(3.6) 7.5 0 0 0 0 7.5
(3.7) 0 10.75 15.75 0 0 26.5
(3.8) 0 8.0 0 0 0 8.0
(3.9) 10.0 0 0 0 0 10.0
(3.10.1) 21.0 20.5 18.5 18.5 18.5 97.0
(3.10.2) 17.2 17.2 17.2 13.0 13.0 77.6
(3.11) 16.0 16.0 0 0 0 32.0
(3.12) 20.5 0 0 0 0 20.5
(3.13.1) 10.0 15.0 15.0 15.0 15.0 70.0
(3.13.2) 0 1.0 1.0 1.0 1.0 4.0

Biodiversity Benefits

Over the past decade there have been numerous reports of amphibian declines and extinctions around the world, including species from Australia. The localities of a number of these Australian species are restricted to alpine, sub-alpine, montane and mountain-top environments in relatively pristine habitats. The factors contributing to the decline or disappearance of these amphibians remain largely unknown. With their biphasic life-history strategy, and skin that is permeable to both liquids and gases, amphibians are considered to be ideal organisms for measuring and monitoring environmental health. Research on, and monitoring of, the Baw Baw Frog (P. frosti) will help to identify, and provide the bases for ameliorating, the causal agents responsible for the decline of this unusual sub-alpine species, and contribute to efforts being made by other amphibian biologists to identify causes of declines in other 'mountain-top' amphibian taxa.

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