Frogs back from the dead

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Greg Roberts | May 26, 2008

QUEENSLAND frogs, feared to be on the path to extinction, have defied the experts by making a comeback.

Frogs from rainforest mountain streams in north and southeast Queensland are returning to areas where they have not been recorded for many years.

"There is a ray of light at last for these animals," said Queensland Parks and Wildlife Service herpetologist Harry Hines.

In a phenomonon that started in the late 1970s, six Queensland frog species became extinct when the chytrid virus invaded their pristine habitat in the rainforest streams.

The fungus infects frog skins, destroying the animals' breathing and nervous systems. Experts believe infection is triggered by a factor such as pollution from agricultural chemicals, increased exposure to ultraviolet radiation, or temperature rises from climate change.

The Queensland extinctions, which included the unique platypus frog, coincided with a worldwide crash in amphibian populations, feared by some observers as the harbinger of impending environmental disaster linked to climate change.

Mr Hines has noted recent increases in numbers of the tiny Kroombit tinker frog in the forests of the Kroombit Tops, near Gladstone in central Queensland.

Three species of closely allied tinker frogs were among the extinction victims of the chytrid virus.

The Kroombit frogs have reappeared at one monitoring site from which they had vanished, and as many as 40 of the amphibians were found at each of several other sites.

Mr Hines said that at several places in the state's southeast and north, species such as the cascade tree frog have returned to areas from which they had long disappeared. "While some species have taken a fair whack, we have gotten to a point where things are reasonably stable," hesaid.

Mr Hines said it was possible frogs were building up immunity to the fungus, or that the disease was becoming less deadly. Alternatively, factors that triggered fungal infection might no longer be present.

He cautioned that populations of some species, while stabilising, were low compared to what they were 20 or 30 years ago. The Kroombit tinker frog was still at risk from the destruction of its rainforest habitat by feral pigs and bushfires.