Southern Corroboree Frog

SPECIES Southern Corroboree Frog
TAXONOMY Pseudophyrine corroboree
STATUS Critically Endangered (ala.org.au); Protected under Australian Law

Designated as a species by John Moore in 1953, the Southern Corroboree Frog is one of Australia’s most critically endangered. It derives its name from the distinctive black and bright yellow stripes having a connection to the Aboriginal Australians ‘corroboree’ where participants at the gathering adorn themselves in white striped markings. It has several genetic and visual differences to the Northern Corroboree cousins (such as a slightly more yellow colouring and different-sized stripes, as well as larger body size).

It only exists in Kosciuszko National Park at elevations between 1300 to 1800 meters above sea level. It lives in sphagnum bogs in the subalpine woodlands, heathlands, and grasslands. Corroboree Frogs tend to breed in water bodies that are dry during the breeding season. Outside the breeding season, Corroboree Frogs have been found sheltering in dense litter and under logs and rocks in woodland and tall moist heath near breeding grounds. 

Lifecycle
Corroboree Frogs have a typical amphibian life-cycle with an aquatic tadpole stage and terrestrial frog stage. The frog reaches sexual maturity after four years and breeding occurs during a short period in summer (January-February). Adult males move into breeding areas in early to late summer. The males make small nests in moss or other soft vegetation and soil at the edges of the breeding pools. Males have a special courtship call to attract females to their nests to mate and lay their eggs. Typically, the pools are dry during the breeding season when the eggs are laid. Females typically lay a clutch of about 25 eggs in a small nest of vegetation near the edge of ponds. The male will remain in his nest through the breeding season and may accumulate many clutches from different females. 

Within the nest, the eggs develop to an advanced stage before development stops and they enter what is called ‘diapause’. This means that the embryos remain, without developing further, until flooding of the nest following autumn or winter rains stimulates them to hatch. After hatching, the tadpoles move out of the nest site and into the adjacent pool where they live for the remainder of the larval period as a free swimming and feeding tadpoles. Corroboree Frog tadpoles are dark in colour, have a relatively long paddle shaped tail, and grow to 30 mm in total length. The tadpoles continue growing slowly, particularly over winter when the pool may be covered with snow and ice, until metamorphosis in early summer. The majority of Southern Corroboree Frogs do not reach reproductive age until four years from metamorphosis.

Threats
The Southern Corroboree Frog has no natural predators because it oozes a toxin (an alkaloid) from its skin. However, it is threatened by human impacts such as climate change, fire and habitat disturbance, feral animals, and the chytrid fungus that has been decimating frog populations around the world. The fungus only infects the tadpoles and adult frogs that have keratin, which it needs to thrive. Frog eggs are immune because they do not contain keratin.

Because Corroboree Frogs typically breed in seasonal wetlands, severe droughts cause mortality of entire tadpole cohorts and contribute to the ongoing decline in populations. Weeds and feral animals also factor into declines as they reduce the quality of breeding habitat.  In January 2014, the entire population of Southern Corroboree Frogs was estimated to be fewer than 50 individuals in the wild. The population has declined by more than 99 per cent since the 1980s.

Updated 5 May 2021