Endangered Northern Corroboree Frog
The Corroboree Frog (Pseudophryne pengilleyi) is a small (25-30 mm) distinctively striped yellow and black frog. These endangered frogs occur only in the higher, colder parts of Australia. There are two species of Corroboree Frog. The Northern Corroboree Frog (Pseudophryne pengilleyi) is found in the Brindabella Ranges in the ACT and adjacent Bogong Mountains and Fiery Ranges in New South Wales. The closely related Southern Corroboree Frog (Pseudophryne corroboree) is found in the Snowy Mountains in New South Wales.
Corroboree Frogs were once abundant where habitat is suitable in these cold mountain areas, but over the past 30 years populations of these frogs have declined and both the Northern Corroboree Frog and the Southern Corroboree Frog are now on the verge of extinction in the wild. The decline of Corroboree Frogs has been attributed to disease caused by the introduced Amphibian Chytrid (pronounced 'Kit-rid') Fungus, which has also caused declines and in some cases extinctions of frogs worldwide. Climate change, environmental stochasticity (drought, wild fires) and damage to habitat by introduced animals (trampling of breeding pools by pigs, deer and horses) may have the contributed to the decline of corroboree frogs in some areas.
The Northern Corroboree Frog is listed as endangered in the ACT, in NSW and nationally. The Northern Corroboree Frog occurs as three main populations that are genetically distinct from one another: a population in the higher elevation areas of the Brindabella and Bimberi Ranges in the ACT, a population in the lower northern part of the Brindabella Ranges in NSW, and a population that occurs though the Bogong Mountains and Fiery ranges in NSW. All populations have declined to very low numbers over the past three decades. In the ACT, where there were once several thousand Corroboree Frogs in the Brindabella/Bimberi Ranges during the early 1980s, recent monitoring suggests there are now less than 10 breeding pairs left from these wild populations.
Corroboree Frogs use two types of habitat; a summer breeding habitat and a winter (non-breeding) habitat. The summer breeding habitat is sphagnum moss bogs and other waterlogged areas such as wet tussock grasslands, fens and tall moist heath. After the summer breeding season (January to March), adult frogs move out of the bogs into the surrounding woodlands and heathlands, where they spend the winter sheltering under logs, rocks and dense leaf litter. The January 2003 wildfires burnt most of the Corroboree Frog habitat in the ACT, though these areas have now regenerated and are again suitable for Corroboree Frogs.
Corroboree Frogs breed in pools that tend to be ephemeral, and are often dry during the breeding season. The males move into the bogs or other wet areas early during the breeding season (January) and call from within damp vegetation (often sphagnum moss) at the margins of pools. The females are attracted to calling males and typically lay a clutch of around 25 eggs out of water in the males' nest chamber in the damp vegetation. The eggs hatch into tadpoles when the water level rises following rain or snow melt (which may be anytime during autumn, winter or spring) and floods the nest. 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 to three years' time they are mature and return to the bogs to breed.
As part of the National Recovery Program for the Corroboree Frog and the ACT Action Plan for the Northern Corroboree Frog, the ACT Government established a captive colony of Northern Corroboree Frogs in 2003 at Tidbinbilla Nature Reserve from eggs collected in the wild. The aim is to maintain a captive 'insurance' colony as a backup in the event that the species becomes extinct in the ACT, and also to release frogs back to the wild to help reverse the decline of wild populations. There are currently around 800 northern corroboree frogs in captivity at Tidbinbilla.
The species has been successfully bred in captivity at Tidbinbilla since 2008. Corroboree Frogs take four years to reach breeding age, and produce only about 25 eggs each year which are then raised for another 2 years before being released back to the wild.
A key aim of the ACT Government recovery program for Northern Corroboree Frogs is to release captive-bred frogs back to sphagnum moss bogs in Namadgi National Park where ecologists hope they will breed and develop natural disease resistance to Amphibian Chytrid Fungus. In 2015, some of the young frogs released in 2011 were heard calling in the bogs, confirming that young captive-bred individuals can survive and grow for several years in the wild to reach breeding age.
The next step in the ACT Government recovery program is to construct five large outdoor enclosures at Tidbinbilla to raise and breed Northern Corroboree Frogs in conditions that more closely resemble what the frogs experience in the wild.