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Thursday, July 29, 2010

SOUTHERN CORROBOREE FROG

When I was a young man I spent a fair bit of time exploring the mountains and plains of Canberra's Brindabella Mountain region. Of particular note was the abundance of small beautiful black and vivid bright yellow striped frogs. One literally only had to look near a creek, soak or bog and there they would be. Around any water source the sound of  frogs permeated the air.


Only officially described in 1953 the Southern corroboree frog (Pseudophryne corroboree)(info here) is now so rare that amphibian specialists seeking them can take weeks to locate an individual frog. The territory for the frog is restricted to a tiny 10 km² area in high country sub-alpine Sphagnum Moss bogs where it has adapted it's lifestyle and breeding functions to endure the climactic extremes of hot dry summers and frozen, snow covered winters. Unusually the frog over-winters up to 300 metres from the bog in bushland under logs and fallen bark and walks overland more like a lizard than a frog with it's four web-less feet.

Southern Corroboree Frog habitats

Corroboree frogs reach maturity when they can breed at around three years of age. They mate in late summer laying their eggs in moss-lined nests made by the smaller male during mid summer around 30cm up on the bank of a bog. From his pre-prepared nest the frog sings his love song to attract females.

Up to 13 females deposit up to 30 pearl-sized eggs in his nest. He is left to guard these eggs until the autumn rains raise the level of the water in the bog and trigger the tadpoles to hatch. The tadpoles then wriggle their way down into the bog where they wait eating algae until they turn into frogs in early summer.


The frog's rapid decline has been mainly from two factors, a fungus and low rainfall.

The Southern corroboree frog, as with other frogs in Australia, has been severely affected by the chytrid fungus (info), a disease that is often fatal. The fungus eats keratin the main protein in frog skin. The frogs skin is not only used for protection but also for breathing and water intake and infected frogs simply suffocate.

The fungus was probably introduced to Australia through the trade of exotic amphibian pets such as Axolotyls and infected frogs arriving in rainforest plants and agricultural produce. The chytrid fungus was first reported in Australia in the 1990's however examination of museum specimens show the fungus has been active in frog populations from as early as 1978. Luckily however the Southern corroboree frog's eggs are immune to the fungus.

Sphagnum Moss Bog

Even though the lifecycle of the corroboree frog can withstand the onslaught of the chytrid fungus it still requires a regular autumn cycle of rainfall. Unfortunately until recently the frogs territory had also been in drought since the early 1980's.

Regular rainfall is required to flood the frogs nest and trigger the tadpoles to emerge whilst assisting them to enter the bog. Even if the tadpoles make it to the bog, if the bog drys out prior to the tadpoles turning into frogs they will perish. The drought has severely impacted on the frog's numbers.

Lets hope some remedy is found for the fungus and that a regular rainfall pattern allows these amazing creatures to repopulate the bogs. I for one would like to be able to show them to my grandchildren.

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