Southern Brown Tree Frog, Litoria ewingii recently photographed at a field site.
Image: Bec Bray
Source: Museum Victoria
Current research by museum herpetologists has found surprising numbers of frogs in areas ravaged by the February 2009 Victorian bushfires.
It seems extraordinary that any frogs remain here given the widespread habitat loss caused by the fires. “The frogs probably survived by sheltering in the dams or in vegetation around the edges,” said Bec Bray, a research assistant working with Curator of Herpetology Jane Melville on this project. “We even got a recapture from last year at the most heavily-burned site at Toolangi.”
The museum holds frog field data for the wider Kinglake area that was collected 40 years ago by Murray Littlejohn. The ten field sites central to the current study have been monitored by PhD candidate Katie Smith for the past three years. Combining the early data with more recent results provides a detailed picture of frog populations before the bushfires. Five species - Crinia parinsignifera, Crinia signifera, Litoria ewingi, Litoria paraewingi and Litoria verreauxi - have been recorded historically at the ten field sites, and all five have been observed after the fires.
In other countries, the full impact of fires on amphibian populations is difficult to assess for some years. Populations may seem to rise immediately after a fire as surviving frogs congregate in the few remaining habitat ponds. “It might be that in future years, the population goes down,” said Bec, who believes that the reduced vegetation around the dams may limit how effectively frogs can breed in the next few seasons.
The team combines a number of approaches for a comprehensive survey. At night, male frogs call from ponds and dams to attract females to breed; since species are easily identified from their distinctive calls, listening at night gives an idea of the species and abundance of frogs around each dam. The night surveys are followed by daytime checks for egg masses and tadpoles in the water and the level of fringe vegetation such as reeds and tree seedlings.
Museum researchers will continue monitoring the field sites in coming years. Since vegetation is important for shelter and to attach egg masses, the succession of regrowth will affect how frog populations recover over the longer term.