Litoria spenceri 

Many amphibians in Australia and around the world have declined in recent years. The Spotted Tree Frog, a mountain stream species from north-eastern Victoria and southern New South Wales, is one such species. The spread of introduced trout coupled with habitat disturbances has reduced the distribution of this species to a few reaches of rocky mountain streams in just 13 river systems. 

More recently, a new amphibian disease, Chytridiomycosis (referred to as Amphibian Chytrid Fungus), is threatening the survival of this species in these remaining refuges. Declines in distribution and abundance throughout its range have resulted in this species being listed as threatened. The Spotted Tree Frog is listed as Endangered under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999.  It is also listed as Critically Endangered on the Victorian Flora and Fauna Guarantee Act 1988 and by the IUCN (2007), and Endangered on the NSW Threatened Species and Communities Act 1995.

Captive breeding for release to support wild populations is an increasingly important element of a coordinated Recovery Program. Zoos Victoria became involved in this program in 1991.

The Program Focus

Of the few populations remaining, all are considered vulnerable to extinction from various threats. Some have relatively stable populations while others are declining, with some on the brink of extinction. The conservation program focuses on:

• Population monitoring to assess the ongoing status of populations and gain knowledge of the population dynamics of the species
• Captive breeding programs to trial re-introduction at sites where the species has become extinct, and to provide insurance backup for wild populations
• Research and evaluation of potential causes of decline
• Habitat protection and management of catchments with respect to other land use practices, weed and fire management

The Conservation Issue

Several factors are considered to be contributing to the decline of the Spotted Tree Frog.  Introduced trout occur in all catchments it occupies and they prey on their tadpoles.  Habitat disturbance from forest management, road works, recreational activities in mountain catchments, such as trail bikes and 4WD vehicles, all contribute to increased erosion, sedimentation of streams, damage to riparian habitat and weed invasion. These disturbances may also have been exacerbated by the extensive bushfires in the region in 2003 and 2006.

A new amphibian disease, Chytridiomycosis (referred to as Chytrid Fungus), is also believed to be a contributing factor to the Spotted Tree Frog's decline. The Chytrid Fungus infects the frogs’ skin, causing damage to the keratin layer, causing death in many species. This disease is thought to be responsible for many amphibian declines in Australia and around the world in recent years.

Zoos Victoria’s Conservation Field Partners

The recovery of the Spotted Tree Frog is the work of several organisations. Each Recovery Team member brings particular expertise to the recovery effort, ranging from captive breeding, habitat management and predator control to education and research.

The recovery program is led by the Victorian Department of Sustainability and Environment  and includes representatives from the following organisations:

Parks Victoria
Department of Environment and Climate change, NSW
Amphibian Research Centre
Department of Environment and Water Resources

The Program Plan

The overall objective of the National Recovery Plan (currently under revision) is to achieve down-listing of the Spotted Tree Frog from Endangered nationally to a lower threat category based on 1994 IUCN Red List criteria of population size and trends, extent of occurrence, and probability of extinction.

The specific objectives of recovery for the Spotted Tree Frog are to:

• Address known or predicted threats to the Spotted Tree Frog
• Ensure that no more Spotted Tree Frog populations become extinct
• Increase our understanding of Spotted Tree Frog biology and ecology, and potentially threatening processes that may be detrimentally affecting the species, in order to better manage the species and its habitat, and to mitigate threats to the species
• Ensure that land use activities will not impinge on the survival of the Spotted Tree Frog
• Encourage community awareness and support for Spotted Tree Frog conservation

Zoos Victoria's Role

Zoos Victoria’s key roles in the recovery of this species are to:

1. Supplement in situ populations through captive breeding for reintroduction.
2. Maintain an insurance population in captivity In the event that the wild population continues to decline.
3. Help with population monitoring programs.
4. Undertake research into the role of Amphibian Chytrid Fungus in population declines.
5. Increase community awareness of the plight of the Spotted Tree Frog and community support for its conservation.

Reports and Publications

Gillesie, G. R. and Robertson, P. R. (1998) Spotted Tree Frog 1998-2002 Recovery Plan. Department of Natural Resources and Environment, September 1998.

Gillespie, G. R. (2000).  Action Statement for the Spotted Tree Frog Litoria spenceri.  Department of Natural Resources and Environment, Victoria.

Gillespie, G. R . (2001a).  Ecology of the Spotted Tree Frog Litoria spenceri: An Investigation of causes of Population Decline.  Unpublished PhD thesis (Zoology), University of Melbourne.

Gillespie, G. R. (2001b).  The role of introduced trout in the decline of the Spotted Tree Frog (Litoria spenceri) in south-eastern Australia.  Biological Conservation 100: 187-198.

Gillespie, G. R. (2002).  Impacts of sediment loads, tadpole density, and substratum on the growth and development of tadpoles of the Spotted Tree Frog Litoria spenceri: an in-stream experiment.  Biological Conservation 106: 141-150.

Gillespie, G. R. and Hollis, G. J. (1996). Distribution and Habitat of the Spotted Tree Frog Litoria spenceri Dubois (Anura: Hylidae), and an Assessment of Potential Causes of Population Declines. Wildlife Research 23: 49-75.