Those Slutty Little Potoroos

Rare potoroo cursed by the pox

Dani Cooper
ABC Science Online

Wednesday, 14 November 2007

A baby Gilbert's potoroo in its mother's pouch (Image: Rebecca Vaughan)
Australia's most endangered marsupial, the Gilbert's potoroo, is suffering from a severe case of syphilis, according to a long-term study.

The disease may affect its ability to reproduce, the study says, further threatening the wild population, which is believed to number fewer than 40.

Murdoch University veterinarian Dr Rebecca Vaughan is now undertaking a penicillin-based trial on a long-nosed potoroo, the nearest relative to the Gilbert's potoroo.

Vaughan, a PhD candidate with the School of Veterinary and Biomedical Sciences, says if the trial at Perth Zoo is successful, researchers will evaluate the feasibility of similar treatment for the Gilbert's potoroo.

Gilbert's potoroo was thought to be extinct for more than 100 years until a small population of about 30 animals was discovered in 1994 at Two Peoples Bay Nature Reserve, near Albany in southwest Western Australia.

The wild population is restricted to 1800 hectares of heath land within the reserve.

Among a range of health conditions, Vaughan has found about 80% of the Gilbert's potoroo population is infected with a form of the bacteria treponema, which is similar to the microbe that causes syphilis in rabbits.

Infected male potoroos suffer severe inflammation of the penis and have a bright green discharge from their bottoms.

Vaughan says in some instances the inflammation is so severe the male potoroos cannot extrude their penis, obviously making it hard for them to mate.

She says syphilis in rabbits decreases rates of conception, placenta retention and leads to neonatal deaths.

Managing populations

Vaughan's research into the health of the critically endangered mammal forms part of the Gilbert's potoroo recovery efforts, co-ordinated by Dr Tony Friend from the Western Australian Department of Environment and Conservation.

Friend says Vaughan's research will help to manage the surviving Gilbert's potoroo population as it will increase knowledge about their susceptibility to disease.

"When you get to such low numbers disease can become significant," he says.

"What we don't understand is if the males are entering fully into breeding and how it is affecting them.

"The question is whether the treponema is affecting the population significantly causing loss of individuals that can't be made up through breeding."

Friend says the Gilbert's potoroo population appears to be stable at Two Peoples Bay and other recovery projects are building up the population.

Thriving elsewhere

While a captive breeding program has met with little success, a group of the marsupials translocated to Bald Island, about 30 kilometres off the coast from Two Peoples Bay is thriving.

From a base population of nine Gilbert's potoroos placed on the island about three years ago, there are now 13 of the guinea pig-like creatures, with the latest generation now ready to breed.

The recovery program is also trialling cross-fostering of young with long-nosed potoroos to allow the original mother a shorter time between young. Two out of three trials have been successful.

Friend says the program is also reintroducing potoroos for breeding into fenced areas away from the main population at Two Peoples Bay.

Within five years he hopes to release Gilbert's potoroos into unfenced mainland areas with a goal of having about 100 Gilbert's potoroos living in the wild.