BANDICOOTS AND BILBIES: Peramelemorphia

PHYSICAL CHARACTERISTICS

Peramelemorphia is an order of small ground-dwelling marsupials known as bandicoots and bilbies. All species in this order live either in Australia, New Guinea, or a few nearby Indonesian islands. Although some of the species in this order have been classified differently in the past, current genetic evidence has led scientists to divide this order into two families, the Peramelidae and the Peroryctidae. The Peramelidae include the true bandicoots of Australia and the bilbies. The Peroryctidae are made up of the spiny bandicoots of the New Guinea rainforest.

Bandicoots and bilbies look like a cross between a rabbit and a rat. They range in size from 6.5 to 23 inches (17 to 60 centimeters), excluding tail length, and weigh from 0.3 to 10.5 pounds (0.1 to 4.8 kilograms). Their tails are usually short in proportion to their bodies.

Bandicoots and bilbies have small pointed snouts and ears that are usually short and rounded. One exception is the greater bilby which has long rabbit-like ears. Most species have thin, rat-like tails, and their fur is usually solid earth tone colors. The fur of the rainforest bandicoots is harsh and spiny.

The front legs of most species in this order are adapted for digging. The front feet have strong claws on toes two, three, and four. Toes one and five are either absent or very small and clawless. The hind limbs are strong and muscular, allowing these animals to leap and hop like a rabbit. However, they are also able to run at a fast gallop. On the hind legs, the bones of the second and third toe are fused, joined into one, but still have separate claws. This pattern of fused toes suggests that these animals may have evolved from the Diprotodonta family.

Bandicoots and bilbies are omnivores, meaning they eat both plants and animals. Members of this order have teeth that are adapted to this diet. Their tooth pattern suggests that they may have evolved from the Dasyuromorphia order (Australasian carnivorous marsupials). Because of the conflicting physical evidence, scientists remain unsure exactly which other marsupial families are their closest relatives.

GEOGRAPHIC RANGE

Species in this order are found only in limited parts of Australia, New Guinea, and the Indonesian island of Seram. In the past, these animals were abundant. They were found in about 70 percent of Australia, throughout New Guinea, and on several other Indonesian islands. Since the beginning of the twentieth century, their range has been drastically reduced by human activities.

HABITAT

The two families in this order live in different habitats. Peramelidae, or true bandicoots and bilbies, live in dry, desert areas, dry grassland, shrubby grassland, open forest, and suburban gardens. Peroryctidae, or spiny bandicoots, live in the tropical rainforests of New Guinea. Several species live in isolated areas at elevations up to 13,000 feet (4,000 meters).

DIET

Bandicoots and bilbies are omnivores, eating both plants and animals, and insects such as ants and termites usually make up most of their diet. They also eat earthworms, insect larvae, insects such as centipedes, and plant parts, such as seeds, bulbs, and fallen fruit. Occasionally larger species eat lizards and mice. They are opportunistic feeders, tending to eat whatever food is available.

Bandicoots and bilbies find food by smell and hearing. Their eyesight is poor. When they locate food underground, they dig cone-shaped holes up to 5 inches (13 centimeters) deep and remove the food with their long tongues. Because so much of their food is dug out of the ground, they also accidentally eat a lot of dirt. Studies have found that between 20 and 90 percent of their waste is earth that was swallowed with the food, then passed through their digestive system. Some species that live in desert areas do not need to drink water. They can get all the moisture they need from their food.

BEHAVIOR AND REPRODUCTION

Most species in this order are nocturnal, active only at night. The exception is the southern brown bandicoot, which is active mainly during the day. All members of this order live alone, coming together only for a short time to mate. Females will mate with more than one male. Many species mate year round. Both males and females are territorial. Males have larger territories than females. Some species mark their territory with scent from a special gland. Males become aggressive when another male enters their territory. Males kept together in captivity will fight.

Most familiar mammals such as dogs, rabbits, and horses, are called eutherian (yoo-THEER-ee-an) mammals. These mammals have a placenta, an organ that grows into the mother's uterus (womb) and lets the mother and developing offspring share food and oxygen until the organs of the developing young mature. Marsupial mammals do not have this type of developed placenta. Most marsupials have what is called a yolk-sac placenta, where there is no sharing of the mother's food and oxygen.

Bandicoots and bilbies are different from other marsupials, because they have a second placenta in addition to the yolk-sac placenta. This placenta resembles the placenta in eutherian mammals, but does not function as well, because it does not attach as closely to the wall of the mother's uterus. As a result, members of the order Peramelemorphia have very short pregnancies, and, like other marsupials, the young are physically immature and undeveloped when they are born. At birth they crawl to their mother's backward-opening pouch where they attach to the mother's teats, or nipples. They are carried inside the pouch until they are mature enough to survive independently.

BANDICOOTS, BILBIES, AND PEOPLE

Aboriginal (native) people hunted bandicoots and bilbies for meat and fur, however these animals were abundant, and hunting did not cause a major decrease in their populations. The coming of European colonists to Australia and New Guinea began the decline of many species of bandicoots and bilbies. Europeans changed the ecology of Australia. They introduced non-native species such as the red fox and the domestic cat, both of which prey on bandicoots and bilbies. They also introduced rabbits that compete with them for food. In addition, Europeans introduced cattle and sheep ranching to Australia. This reduced the habitat suitable for many species of bandicoots and bilbies. Finally, native people regularly burned the grassland, and the plants that grew after the burn provide a good habitat for bandicoots and bilbies. This practice changed after large scale livestock ranching began, creating less diverse habitats that did not support these native species well.

The number of bandicoots and bilbies has decreased dramatically since the beginning of the twentieth century. Three species have gone extinct. Conservation organizations are tying to provide safe habitat for these animals by fencing preserves and controlling predators, animals that hunt them for food. However, people living in suburban areas still tend to think of bandicoots and bilbies as pests, because they dig up lawns and gardens when hunting for food.

CONSERVATION STATUS

Since the coming of European colonists in 1770, three species have gone extinct: the pig-footed bandicoot, the desert bandicoot, and the lesser bilby. The number of animals in four other species has dropped to dangerously low levels and they are considered Endangered, facing a very high risk of extinction in the wild, or Vulnerable, facing a high risk of extinction in the wild. So little is known about most of the species in the Peroryctidae family that their conservation status cannot be accurately evaluated.

YOU DIRTY BANDICOOT

Bandicoots reminded European settlers in Australia of rats. They had a very low opinion of the animal. Today in Australia the word "bandicoot" when applied to a person is considered a mild term of abuse and disrespect.

Since the 1980s captive breeding and conservation programs have succeeded in increasing the number of bilbies. The Australian Bilby Appreciation Society has developed public relations programs to increase awareness of the need to protect these animals. They have also raised money for a fenced preserve, because bilbies cannot thrive in the wild without predator control. Other species have been the focus of less conservation awareness and continue to decline.

FOR MORE INFORMATION

Books:

Finney, Tim F. Mammals of New Guinea, 2nd ed. Ithaca, NY: Cornell University Press, 1995.

Menkhorst, Frank. A Field Guide to the Mammals of Australia, 2nd ed. Oxford, U.K.: Oxford University Press, 2001.

Nowak, Ronald. M. Walker's Mammals of the World. Baltimore: Johns Hopkins University Press, 1995.

Periodicals:

Smyth, Chris. "Bilbies' Call of the Wild." Habitat Australia (October 1998): 13.

Web sites:

"Nature Conservation" Queensland Government Environmental Protection Agency/Queensland Parks and Wildlife Service. http://www.epa.qld.gov.au/nature_conservation (accessed on May 14, 2004).

University of Michigan Museum of Zoology. "Order Peramelemorphia." Animal Diversity Web.http://animaldiversity.ummz.umich.edu/site/accounts/information/Peramelemorphia.html (accessed on June 30, 2004).

Other sources:

Australian Bilby Appreciation Society. P. O. Box 2002, Rangview, Victoria 3132 Australia. E-mail: [email protected] Web site: http://members.oze-mail.com.au/bilbies.