Amphibians
Northern Corroboree Frog
Pseudophryne pengilleyi · also called corroboree frog
In the sphagnum bogs high in the Australian Alps lives a frog the size of a thumbnail, striped in vivid yellow and black like ceremonial body paint. The northern corroboree frog is one of the very few animals that manufactures its own poison, and it is also one of the most endangered amphibians on Earth, kept from extinction only by a network of zoos.
Overview
Pseudophryne pengilleyi is a tiny frog, about 2.5 to 3 cm long, boldly striped in yellow-green and black. It walks rather than hops, relying on its warning colours rather than speed. It lives only in the sub-alpine bogs and wet heath of the Brindabella and Fiery Ranges on the ACT and New South Wales border, at 750 to 1,800 m.
A frog that makes its own toxin
Most poisonous frogs, including the South American poison dart frogs, get their toxins from their food. Corroboree frogs synthesise their own alkaloids in the skin, so even a zoo-bred frog on a harmless diet is toxic. The vivid stripes are an honest warning, and the name comes from a word for an Aboriginal ceremonial gathering.
A slow life, and a collapse
The frog takes four years to mature and can live to ten, and it breeds slowly, the male guarding a small clutch in a moss chamber until autumn floods the nest. That slow life has left it unable to withstand the amphibian chytrid fungus, which has driven the wild population from tens of thousands to a few hundred and then near zero, with drought, feral animals, and the 2003 and 2019-20 bushfires making it worse.
Status
The northern corroboree frog is Critically Endangered. It survives mainly as a captive insurance population at Tidbinbilla, Taronga, Melbourne, and Healesville, with captive-bred eggs and frogs released into disease-refuge enclosures in the mountains.
Northern Corroboree Frog: common questions
What is the difference between the northern and southern corroboree frog?
They are two closely related species that were only formally separated in the 1990s. The southern corroboree frog, Pseudophryne corroboree, lives in Kosciuszko National Park in New South Wales and has broad, bright yellow stripes. The northern corroboree frog, Pseudophryne pengilleyi, lives further north in the Brindabella and Fiery Ranges around the Australian Capital Territory and tends to have narrower, more greenish-yellow stripes and a slightly smaller body. Both occupy the same kind of high-country sphagnum bog, both make their own skin toxins, and both are Critically Endangered and dependent on captive breeding. Genetic and call differences confirm they are distinct species rather than variants of one.
How does a frog make its own poison?
Corroboree frogs and their relatives in the genus Pseudophryne produce a group of alkaloid toxins, including pseudophrynamines, in glands in the skin. Unlike the famous poison dart frogs of South America, which cannot make their toxins and instead extract them from a diet of particular ants and mites, corroboree frogs manufacture theirs from scratch through their own biochemistry. The proof is that frogs bred in zoos on a standard diet of pinhead crickets and fruit flies, which contain none of the raw materials a dart frog would need, still develop toxic skin. This makes the corroboree frogs one of very few vertebrates known to synthesise their own defensive alkaloids.
Why did the northern corroboree frog become so endangered?
The single biggest cause is chytridiomycosis, the disease caused by the amphibian chytrid fungus, which arrived in the Australian Alps in the 1980s and attacks the skin that frogs use to breathe and balance their salts. Corroboree frog numbers fell steeply through the 1980s and 1990s and have kept falling. On top of the disease, the high-country bogs the frogs need have been damaged by drought, by trampling and wallowing from feral horses, pigs, and deer, and by two severe bushfire seasons, in 2003 and again in 2019 to 2020, which burned through parts of the range. Because the frog breeds slowly and lives in only a small area, it has no capacity to recover on its own.
Can the northern corroboree frog be saved?
There is a serious, long-running effort to do so, but the outcome is not certain. A captive insurance population is maintained at Tidbinbilla Nature Reserve, Taronga Zoo, Melbourne Zoo, and Healesville Sanctuary, holding thousands of frogs and eggs so the species cannot be lost entirely. Managers release captive-bred eggs and frogs into the wild, increasingly into purpose-built enclosures and artificial pools designed to reduce chytrid exposure, and research continues into disease resistance and possible treatments. Some released frogs have survived and bred. But as long as the chytrid fungus remains in the environment and the frog cannot yet persist without human help, it stays Critically Endangered.