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Science EncyclopediaScience & Philosophy: Ballistic galvanometer to Big–bang theory

Australian wildlife holds many surprises, but few as intriguing as the widely distributed bandicoots. These small, rabbit-sized marsupials have a thick set body, short limbs, a pointed muzzle, short neck and short hairy tail. Their teeth are similar to those of insect- and flesh-eating mammals, but their hind feet resemble those of kangaroos and possums. The hindfeet are not only considerably longer than the front pair, which gives most bandicoots a bounding gait, but the second and third toes of the hind foot are fused together, with only the top joints and claws being free. The forefeet, in contrast, have three prominent toes, with strong claws used for digging and searching for insect prey. The fused toes of the hind limbs not only provide a strong base for a hopping animal, but also make a highly effective comb for grooming dirt and parasites from the fur. One species now thought to be extinct, the pig-footed bandicoot (Chaeropus ecaudatus), had a slightly different morphology, with only two toes on their forefeet and one on the hindfoot—adaptations for running, as this was a species of the open plains.

The taxonomic status of bandicoots is still uncertain, although two families are now recognized—the Peramelidae, with some 13 species, and the Thylacomyidae, with just one species represented, the greater bilby Stuffed specimen of a pig-footed bandicoot. Photograph by Tom McHugh. The National Audubon Society Collection/Photo Researchers, Inc. Reproduced by permission. (Macrotis lagotis). All of these species are unique to the Australian region, specifically mainland Australia, Tasmania, New Guinea and several offshore islands. Within this range, however, bandicoots have adapted to a wide range of habitats, including arid and semi-arid regions, coastal and sub-coastal habitat, savannah and lowland and mid-montane rainforest. On New Guinea, some species have been recorded at an altitude of 5,000 ft (1,500 m). The animals themselves may also vary considerably in size and appearance. The smallest species Microperoryctes murina weighs less than 4 oz (100 g), while one of the largest Peroryctes broadbenti may weigh more than 11 lb (5 kg).

Bandicoots are terrestrial and nocturnal species, constructing shallow burrows and surface nests beneath vegetation. The greater bilby is the only species that constructs a large burrow system, which may extend 7 ft (2 m) underground. Bandicoots are normally solitary, with males occupying a larger home range (4.2–12.8 acres, or 1.7-5.2 ha) than females (2.2–5.2 acres, or 0.9-2.1 ha). Despite their genteel appearance, males, in particular, can be very aggressive towards other males. Little is known of the social behavior of most species, but they are thought to defend a central part of their ranges, especially the area surrounding their nest, against other animals. Males do not cooperate with bringing up the litter.

In the wild, bandicoots feed mainly on insects and their larvae but they are opportunistic feeders and will also consume fruit, berries, seeds, and fungi. Prey is either dug out of the soil or gleaned from the surface; their long, pointed snout is probably an adaptation for poking into tiny crevices or foraging under leaf litter for insects. Bandicoots have a keen sense of smell which is probably the main way in which they locate food at night. Most species also have prominent ears which may also assist with locating moving prey. Some species, such as the greater bilby have long naked ears that probably help with thermoregulation, as this species is adapted to living in arid conditions.

As with all marsupials the young are born at a very early stage of development, usually after a gestation period of just 12 days—one of the shortest periods of any mammal. When they are born, young bandicoots measure less than an inch (about 1 cm) and weigh a fraction of an ounce (0.2 g). Following birth the infant, which has well developed forelimbs, crawls its way into the mother's pouch where it attaches to a nipple and where it will remain for much of its pouch life. The average litter size is four; litters of seven young have been recorded. As the young grow, the mother's pouch increases in size to accommodate her developing family. Juveniles remain in the pouch for about 50 days, after which the mother begins to wean them. By the time they are seven weeks old, they are covered with short hair and the eyes are open.

Where climate and food conditions are favorable, bandicoots may breed throughout the year—females of some species may even become pregnant before its current litter is fully weaned. Bandicoots therefore have a very specialized pattern of breeding behavior among the marsupials, with a pattern of producing many young in a short period of time and with little parental investment.

Despite these adaptations, many species are now threatened as a result of human activities. Bandicoots have proven to be highly vulnerable to habitat modification and predation from introduced predators. In Australia, large areas of former brush habitat have been converted into rough pasture for sheep and cattle grazing, whose close cropping feeding actions have had a considerable effect on the soil microhabitat. Overgrazing by rabbits has had a similar effect. Introduced predators, especially foxes, cats and dogs have also had a major impact on populations in some areas. In New Guinea, many species are trapped for their fur and meat, but current levels of exploitation are unlikely to pose a significant threat to most species.

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