PYGMY POSSUMS: Burramyidae

PHYSICAL CHARACTERISTICS

Pygmy possums, like most animals native to Australia and New Guinea, are marsupial mammals. This type of mammal, unlike familiar eutherian (yoo-THEER-ee-an) mammals such as dogs, cats, or humans, does not have a well-developed placenta. A placenta is an organ that grows in the mother's uterus (womb) during pregnancy in order to share food and oxygen with the developing young. Since marsupial mammals like pygmy possums do not have a well-developed placenta, their young are born hairless, blind, and underdeveloped and must complete development inside their mother's pouch.

Pygmy possums look much like common mice. They are small, between 2 and 4 inches (5 to 10 centimeters) long, and they weigh between 0.2 and 1.4 ounces (7 to 40 grams). They are covered with soft fur that is brown on their backs and lighter underneath.

GEOGRAPHIC RANGE

Pygmy possums live in central New Guinea, Tasmania, and southeastern and southwestern Australia.

HABITAT

Most pygmy possums live in wet forest areas with evergreen or eucalyptus (yoo-kah-LIP-tus) trees. One species, the mountain pygmy possum, lives in the tropical mountain rainforest of New Guinea above 4,900 feet (1,500 meters).

DIET

Different species of pygmy possums have different diets, ranging from plant pollen and nectar to insects to small lizards. The long-tailed pygmy possum eats mainly insects, but will also feed on flowers. The eastern pygmy possum eats mainly pollen and nectar. The mountain pygmy possum eats seeds, fruit, insects, and other small animals. All species of pygmy possum are eaten by owls, feral (wild) cats, snakes, and carnivorous (meat-eating) marsupial mammals.

BEHAVIOR AND REPRODUCTION

Pygmy possums are nocturnal, which means that they sleep during the day and are active at night, although a few species may come out on cloudy days. All but one species live in trees and are good climbers, using their prehensile (grasping) tail to help them climb. These tree-dwelling pygmy possums build nests inside tree hollows using leaves and other plant material. As many as five possums live in a shared nest.

SEX SEGREGATION

Mountain pygmy possums have a social structure unlike any other members of this family. Groups of up to ten related females (mothers, daughters, grandmothers) share a home range high on the mountain. The males live together lower down the mountain and visit the females only to breed. Unlike many species, the males are not aggressive to each other and do not seem to mind this separation of the sexes.

The female pygmy possum has four teats, or nipples. This is the maximum number of young that she can raise, although the usual number is one to three young, once or twice a year. She raises the young without any help from the male. After birth, she carries the young in her pouch until they reach an appropriate size, around 0.2 ounces (7 grams). They then spend time in the nest until they reach about 0.35 ounces (10 grams), after which they become independent. Although not much is known about how long some species live, female mountain pygmy possums live about eleven years, while males live only four, an unusually large difference in lifespan.

The mountain pygmy possum lives in mountain meadows and rock fields. It is very different from other pygmy possums. It lives at high elevations between 4,265 and 7,300 feet (1,300 and 2,230 meters), where there is snow on the ground at least three months out of the year. It shares a nest with other possums of the same sex, and stores up fat to survive the winter. One individual was found in autumn that weighed almost three times its normal weight. In the winter, the mountain pygmy possum can reduce its heart rate, energy use, and body temperature and remain inactive for up to twenty days at a time.

PYGMY POSSUMS AND PEOPLE

Pygmy possums are not known to have any significance to humans except to those interested in scientific study. Species that feed on plant nectar and pollen may be responsible for helping to extend the range of these plants.

CONSERVATION STATUS

The mountain pygmy possum is considered Endangered because of the very limited area (only two places in Victoria, Australia) in which it lives. Disturbances to its habitat are considered the most important threat. A natural threat is the annual change in rainfall. The amount of rain affects the size of the Bogong moth population—this in turn affects the amount of food that is available for the mountain pygmy possum, which gorges on Bogong moths almost exclusively during the summer months.

EASTERN PYGMY POSSUM (Cercartetus nanus): SPECIES ACCOUNT

Physical characteristics: Eastern pygmy possums grow to a length of between 7 and 8 inches (18 to 20 centimeters). They have brown fur, except on their belly, which has gray fur. The base of their tail is thick because of stored fat in that area. Eastern pygmy possums also have long tongues with bristles on the tip like a brush.

Geographic range: This species lives in Tasmania and in eastern and southeastern regions of Australia.

Habitat: Eastern pygmy possums live in open forests, shrubby woodlands, and rainforests.

Diet: These possums are omnivorous. They eat nectar and pollen as well as insects. More insects are eaten by individuals that live in wet areas where plants bloom less continuously.

Behavior and reproduction: Eastern pygmy possums are solitary animals. They build nests out of leaves and bark inside of tree-hollows. The female is mature at about five months of age. She gives birth to one to three young twice each year. The young are born after a month-long pregnancy. They remain in the pouch for about forty-two days, and stay in the nest another three weeks before becoming independent at the age of about two months.

Eastern pygmy possums and people: Eastern pygmy possums hold no known significance to humans beyond scientific interest.

Conservation status: This species is not considered to be threatened. ∎

FOR MORE INFORMATION

Books:

Mansergh, I. M., Linda Broome, and Katrina Sandiford. The Mountain-Pygmy Possum of the Australian Alps (Australian Natural History). Kensington, Australia: New South Wales University Press, 1994.

Steiner, Barbara A. A Field Guide to the Mammals of Australia. Oxford, U.K.: Oxford University Press, 2001.

Web sites:

Lamington National Park. "Eastern Pygmy Possum." http://lamington.nrsm.uq.edu.au/Documents/Anim/eastern_pygmy_possum.htm (accessed on June 30, 2004).

"Royal's Hidden Population of Pygmy Possums Astounds Researchers." Australian National Parks and Wildlife Service. http://www.nationalparks.nsw.gov.au/npws.nsf/Content/Royals+hidden+population+of+pygmy+possums+astounds+researchers (accessed on June 30, 2004).