World's oddest creature at risk from killer fungus

It is a unique Australian creature - a mammal that lays eggs, and has a furry body, a bill like a duck's and webbed feet. The males are also poisonous. But in Tasmania, one of its principal habitats, the platypus is under threat from a deadly fungal disease.

More than one-third of the population is believed to have been wiped out in the north of the island state, and there are reports that the disease has now spread to southern areas. It is almost always fatal, causing ulcers that turn into gaping wounds.

The shy, solitary platypus inhabits the waterways of Tasmania and the eastern Australian mainland. The same fungus is found on the mainland, where it kills amphibians, particularly Queensland's green tree frogs. But it does not affect platypuses there.

Niall Stewart, a research fellow at the University of Tasmania, believes that the tiny frogs may have carried the fungus into Tasmania in bunches of Queensland bananas. "Platypuses on the mainland have evolved with the fungus, and so they're immune," he said. "But the poor platypuses here haven't seen it before." The island is a haven for platypuses, thanks to its abundant waterways. But Dr Stewart, who has carried out extensive field work, believes that 35 per cent are falling victim to the disease in the affected areas.

Dr Stewart said nothing was being done to combat the disease. He has repeatedly failed to secure research funding. The problem has been overshadowed by a rare cancer that has killed half of the wild population of another native animal, the Tasmanian devil, and threatens the species' survival.

The ulcers, which appear on a platypus's broad tail or hips, grow to up to 10cm in diameter. Death is usually caused by secondary bacterial infections, or from depletion of body fat, most of which is stored in the tail. The wounds also prevent the platypus from keeping warm in cold water.

It is not known how the disease is transmitted - possibly by ticks, or by males fighting, or via burrows. Dr Stewart said it was feasible that mud containing fungal spores was being carried into new areas on hikers' boots or 4x4 vehicles.

Asked if the Tasmanian platypus could develop immunity, he replied: "Possibly, in a few hundred thousand years. The problem is that mature animals with ulcers are still capable of breeding, so they're producing more susceptible animals. It would take a long time for natural selection to sort it out." The platypus is one of only three monotremes - egg-laying mammals - in the world. The others are Australia's two species of echidna, or spiny anteater.