Endangered Northern Corroboree Frog

Corroboree Frog image1

Endangered Northern Corroboree Frog (Pseudophryne pengilleyi)

Corroboree Frogs are small (25-30 mm) distinctively striped yellow and black frogs. They occur in a restricted, high-altitude distribution in waterlogged grasslands, heath, sphagnum moss bogs and adjacent woodlands (Osborne 1989). Adult Corroboree Frogs spend most of their time in the woodlands (where they also over-winter) and move into the sphagnum moss bogs and other waterlogged areas during summer to breed. Females lay clutches of around 25 eggs in damp vegetation at the margins of pools. The eggs hatch into tadpoles when the water level rises following rain or snow melt (which may be anytime during autumn, winter or spring). The tadpoles metamorphose into frogs during the following summer (one year after eggs were laid) and move out of the bogs to the woodlands. In a further two years time they are mature and return to the bogs to breed.

Since 1997 two species of Corroboree Frog has been recognised; the Southern Corroboree Frog Pseudophryne corroboree and the Northern Corroboree Frog Pseudophryne pengilleyi. The Southern species is found in the Snowy Mountains (New South Wales), whereas the Northern species occurs in the Bimberi and Brindabella Ranges in the ACT and adjacent Bogong Mountains and Fiery Ranges in New South Wales (ACT Government 1997). Both species have suffered severe declines over the last two decades leading to concerns over their future survival in the wild.

The decline of Corroboree Frogs is most likely part the world-wide phenomenon of declining frog species. Probable causes of decline of Corroboree Frogs are introduced disease (Chytrid fungus), climate change and environmental stochasticity (drought, recent wild fires). These factors may also have been exacerbated by ecological changes subsequent to European settlement, such as changed grazing and burning regimes, and disturbance from introduced animals.

The Northern Corroboree Frog is listed as threatened in the ACT, in NSW and nationally. Although the populations in the Fiery Ranges and Bogong Mts in NSW have declined, they are still relatively secure. In contrast, the Brindabella/Bimberi populations (which genetically distinct from the NSW populations) have declined to very low numbers over the last five years. Where there were once a few thousand adult frogs in the Brindabella/Bimberi ranges during the early 1980s, recent monitoring suggests there are now less than 100 breeding pairs left. The January 2003 wildfires burnt most of the Corroboree Frog habitat in the ACT (Brindabella/Bimberi Ranges), although frogs are now using the regenerating areas.

As part of the National Recovery Program for the Corroboree Frog and the ACT Action Plan for the northern species, a captive husbandry program has commenced at Tidbinbilla Nature Reserve. The program involves collecting eggs from the wild and raising them in captivity to mature frogs, which dramatically increases the survival rates of these individuals. Progeny of the captive husbandry program will be released back to the wild to augment the size of wild populations, helping them buffer environmental disturbance. A self-sustaining (breeding) captive population will help safeguard the species against extinction should wild populations disappear. However, a self-sustaining captive population of either of these species has not yet been achieved, and further research into husbandry is required.