Conservation

Six species of diprotodont marsupial are known to have gone extinct in recent years, among them the Toolache wallaby, Macropus greyi. This once abundant native of South Australia was one of the swiftest of all macropods. Its agility and its very fine pelt made it a favorite quarry for "sportsmen" and it was hunted to the brink of extinction in the 1920s. The species may have hung on in some parts of its former range until as late as the 1970s, but here have been no positive records since 1924 and the species is listed as extinct. Another victim of changing times was the broad-faced potoroo—this was first described in 1844, but was extinct within 40 years.

Of the remaining diprotodont species, approximately a quarter currently appear on the IUCN Red List of Threatened Animals. In New Guinea these include the black spotted cuscus and Goodfellow's tree kangaroo and in Australia the long-nosed potoroo, the Proserpine and yellow-footed rock wallabies, the brush-tailed bettong, and the mountain pygmy possum. Two species, the Gilbert's potoroo and the Northern hairy-nosed wombat are Critically Endangered, both with less than 50 individuals left in the wild. A further quarter of all diprotodonts are regarded as Near Threatened or data deficient. This latter designation means the animals, or at least their distribution and abundance, are so little known that conservationists have been unable to assess the extent of any potential threat.

The problems facing many threatened diprotodonts are very similar. In Australia the arrival of humans and their companion animals has had a devastating effect on native wildlife, in terms of habitat modification, hunting and predation by introduced carnivores. The first aboriginal settlers arrived between 60,000 and 40,000 years ago. They introduced the semi-domesticated dingo and began managing the landscape using burning regimes to encourage fresh plant growth. However these changes were minor compared to those that came about with the arrival of European settlers in the late eighteenth century. The advance of farming, the intensification of burning regimes, and above all the deliberate introduction of foxes, cats, and rabbits, had a profoundly destabilizing effect. In New Guinea, there are two main threats to native diprotodonts, most of which are forest-dwellers. Unrestricted logging not only destroys habitat, it also opens up areas of previously inaccessible forest to hunting.

On a more positive note, several species of diprotodont that were once considered extinct have been rediscovered alive and well. While most of these are still very rare, being endangered is still very much better than being extinct. Gilbert's potoroo was presumed extinct until 1994 when a small colony was rediscovered on the coastal heathland near Albany in Western Australia. A captive breeding program is underway. Leadbeater's possum was declared extinct in the early twentieth century, but turned up again in 1961. Ironically it appears to have been saved by the enormous bush fires that devastated large areas of the Victorian Highlands in 1939—the standing dead wood left by the fire provided a sudden surplus of suitable possum nesting holes. The mountain pygmy possum had never been seen alive before 1966. The species had been described from preserved remains and

A bridled nail-tailed wallaby (Onychogalea fraenata) on a scientific reserve in central Queensland, Australia. This wallaby was presumed extinct in the 1960s but was rediscovered in 1973 in a small area of Queensland, Australia. (Photo by Mitch Reardon/Photo Researchers, Inc. Reproduced by permission.)

A bridled nail-tailed wallaby (Onychogalea fraenata) on a scientific reserve in central Queensland, Australia. This wallaby was presumed extinct in the 1960s but was rediscovered in 1973 in a small area of Queensland, Australia. (Photo by Mitch Reardon/Photo Researchers, Inc. Reproduced by permission.)

was presumed long extinct, when one turned up alive and well in a ski lodge in the winter resort of Mount Hotham. Other resurrected diprotodonts include the parma wallaby and the Mahogany glider.

There are also some conservation success stories—perhaps most notably the koala. In 1920, the species was facing extinction due to overhunting and habitat fragmentation. Thanks to a ban on hunting and the establishment of many reserves, the trend was reversed. In fact in many ways the campaign to save the koala has been too successful. Many reserves are now so overcrowded that disease has become a serious issue. While the future of the species appears secure, the outlook for many thousands of individuals living on overcrowded reserves is rather bleak. At best they face deportation to new homes (of which there are a dwindling number), at worst a slow death from infections such as Chlamydia. In some places, wildlife managers have had to make the unhappy decision to cull some the animals they have work so hard to save in order to improve living conditions of others.

The northern hairy-nosed wombat, Lasiorhinus krefftii, is now Critically Endangered. Its southern cousin Lasiorhinus latifrons is faring a little better, but still has a rather restricted distribution. The common wombat, Vombatus ursinus, while not officially threatened, is regarded as a pest in some states and is becoming a cause for conservation concern.

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