At the beginning of the twenty-first century, there are some signs that the downward trend in the fortune of bandicoots may at least be slowing. In the previous century, three species had plummeted to extinction even before scientists had gained a clear understanding of their ecology. Today, the IUCN lists (as of 2002) the golden (Isoodon auratus) and eastern barred bandicoot (Perameles gunnii) and greater bilby as Vulnerable and the western barred bandicoot (Perameles
bougainville) as Endangered. Seven New Guinea species are given a Data Deficient rating.
The factors which caused catastrophic declines in Australian bandicoot populations and distribution during the nineteenth and twentieth century are still of paramount significance. Continued intensive grazing by cattle and sheep of former bandicoot habitat over much of the continent ensures that there is no realistic possibility of recolonization without major changes in land management. In Victoria, for example, the hummock grassland of kangaroo and wallaby grass was largely removed in favor of ryegrass and clover to feed grazing livestock. A lack of floristic diversity meant that there was not enough food, or shelter from predators and adverse weather to sustain the population of western barred bandicoots.
Even supposing that livestock grazing could be reduced or eliminated, an added complication is the presence of introduced predators, especially foxes and cats. The arrival of cats on Hermite Island in Western Australia caused the extinction of the golden bandicoot from that island, for example. There is also evidence that bandicoot populations are being suppressed by transmission from cats of toxoplasmosis. Introduced rabbits have also been a major cause of population declines through competition for food and habitat.
While captive breeding programs for greater bilbies and eastern barred bandicoots have proved fruitful, a prerequisite of successful reintroductions into the wild appears to be the exclusion of predators, together with control of rabbits and kangaroos. Exclusion by use of fences can only be effective over very small areas. In some unfenced areas where bandicoots are present, conservation authorities are attempting to limit predation. In Sydney, the National Parks and Wildlife Service began a fox control program in 2001, using the presence of the southern brown bandicoot as an indicator of success.
Colonies of bilbies and western barred bandicoots are being bred at a special facility within the Francois Peron National Park in Western Australia under the Project Eden conservation program, started in 1995. These colonies are supplemented with animals from breeding programs at other agencies such as the Kanyana Wildlife Rehabilitation Centre (bilby, western barred bandicoot) and are slated for the reintroduction phase of the program.
Scientists are still exploring the relative significance of other factors in bandicoot declines. In Western Australia, for example, the extinctions of the pig-footed bandicoot and desert bandicoot are now thought to have been precipitated by the aborigines abandoning traditional burning practices starting in the 1930s. The replacing of mosaic selective burning by uncontrolled wildfires over very large areas left these less mobile species unable to escape.
The conservation of some species is hindered by the fact that they do not live conveniently within protected areas. One fifth of Tasmania consists of nature preserves, yet this does not protect bandicoots, since they live largely on the periphery or outside of these sanctuary zones.
The conservation status of several bandicoot species in New Guinea remains something of a mystery. Seven species are classified by the IUCN as Data Deficient. Partly, this is a reflection of their location in remote and often inaccessible mountain rainforest habitat. But bandicoots are also notoriously difficult to trap. Their preference for natural rainforest food rather than artificial bait means that population monitoring is extremely difficult. Hunting is widespread and common in New Guinea and its islands, but without proper censuses, it is almost impossible to detect whether it is having a deleterious effect.
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