By Craig Cormick
In October 1992, William the wombat, who had been raised in captivity since his youth, was released into the bush of Victoria. He was wearing a radio tracking collar, provided by the Finnish telecommunications company Nokia, and his movements were carefully monitored.
William displayed a greater affinity for human habitats than for the wild; he was found hanging around suburban gardens before returning to the gates of the Healesville Sanctuary, which had cared for him prior to his release.
As a wild wombat, William was a bit of a failure. Still, he was one of the lucky ones. Of the many thousands of animals returned to the wild in Australia each year, most fail to adapt and are killed by feral cats or foxes.
Australia does not have a good record for conserving its native mammals. Since Europeans settlers arrived over 200 years ago, introducing European animals and European methods of farming, an estimated 18 mammal species have become extinct.
According to Dr Melody Serena, a conservation biologist with Species Survival Australia, about half the number of recently extinct mammals in the world have been Australian.
Dr Serena said the reasons for extinction were basically two: the destruction of native habitats as land was cleared for agriculture, and introduced predators such as cats and foxes.
Also, changed fire regimes of fewer but larger fires in the bush, as dramatically demonstrated in NSW recently, can lead to both changed habitats and the potential wiping out of isolated species living in remote bush areas.
There are currently 23 mammal species in Australia which are considered endangered. Some can now be found only in very isolated areas or on offshore islands, where no predators were ever introduced.
However, the good news for such animals is that there are programs being run across Australia to reintroduce them to the wild.
Some include reintroducing mammals from offshore islands to special enclosures. In Western Australia the Herisson Prong peninsula, near Shark Bay, has been fenced off for the reintroduction of the burrowing bettong — or boodie — from the offshore islands where the last members of the species still live.
Trials are also under way to extend the habitats of some numbats. They were once widespread over the southern half of Australia, but can now be found only in small patches of forest in southern WA.
In Victoria, researchers based at the Healesville Sanctuary, north-west of Melbourne, are working to reintroduce the small brush-tail phascogale to wider areas.
Dr Serena said the trick was to ensure the animals being reintroduced could be protected from predators, which meant either eliminating foxes and cats through baiting before native animals were reintroduced, or conditioning native animals to the dangers of predators.
Some programs take on a bizarre twist. In an attempt at conditioning the endangered rufous hare wallaby to conditions on mainland Australia, where it has been extinct in the wild for several years, researchers have mounted stuffed cats and foxes on skateboards which are wheeled at the small wallabies, accompanied by tape recordings of one of the wallabies' alarm calls.
Another variation has a stuffed predator fitted with puppet strings, leaping at the wallabies while they are squirted with water from water pistols.
Results of reintroduction programs have been mixed. In WA, all the radio-tracked boodies released into the wild in 1992 were killed by cats in the first week. But in Victoria, where brush-tailed phascogales have been introduced gradually into the wild as weaning infants, they have demonstrated a much higher survival rate.
Exact numbers of feral cats and foxes are not known, but 20,000 cats are destroyed each year in the state of New South Wales alone.
The animals most vulnerable to extinction have been in the weight range of 35 grams to 5.5 kilograms, which are generally possums, bandicoots and wallabies, particularly those that lived in arid and semi-arid habitats with little cover.
At the Healesville Sanctuary, large numbers of injured animals are brought in each year by the public. After treating them, the sanctuary attempts to return them to their natural habitats.
However, as William the wombat demonstrated, after long periods of being fed and cared for, returning to the wild can be difficult.
Lynda Sharpe, a zoologist working at the Healesville Sanctuary, said, "They have a lot of trouble psychologically being thrust out into the wild".
In Melbourne alone, according to Sharpe, about 2000 possums are removed from suburban roofs each year, where they often live in the roof cavity, and are returned to the wild. About 88% of them died in the first week.
However, through intensive radio tracking programs, researchers are learning a lot more about the behaviour of animals released into the wild and are adapting programs to increase their survival chances.
Also, researchers at the CSIRO are studying genetically engineering a virus that may sterilise foxes and other predators. "But that is a big question mark", Dr Serena said.
There is a growing interest in reintroducing animals. A symposium on Reintroduction Biology of Australasian Fauna, held at the Healesville Sanctuary late last year, attracted more than 180 delegates from Australia and New Zealand.
Despite some setbacks in reintroduction trials, Dr Serena is optimistic, saying, "As long as the will is there, there's no reason that what has been lost over large areas can't be put back again".
As for William the wombat, he was deemed fundamentally addicted to human habitats and was transferred to a wildlife centre for care, where he will live out his years, protected from the perils and the traumas of his native habitat.