MUSKY RAT-KANGAROO: Hypsiprymnodontidae

PHYSICAL CHARACTERISTICS

The musky rat-kangaroo is a small, four legged, marsupial mammal. It is different from most familiar mammals such as cats, dogs, and horses, which are known as placental or eutherian (yoo-THEER-ee-an) mammals. Eutherian mammals have a placenta, an organ that grows in the mother's uterus (womb) and lets the mother and developing offspring share food and oxygen. Marsupials do not have a well-developed placenta. Consequently, they give birth to young that are physically underdeveloped. These young are hairless, blind, and have immature organ systems. They are unable to survive on their own. Instead, after birth they are carried around for several months in their mother's pouch, where they are attached to the mothers teats, or nipples. They are carried and fed this way until they have grown and matured enough to fend for themselves.

Musky rat-kangaroos are fairly small. Their bodies are generally between 6 and 11 inches (15 to 30 centimeters), and they have a total length from nose to tip of the tail of about 11 to 17 inches (30 to 43 centimeters). Musky rat-kangaroos have short brown or reddish fur that is very soft on their backs, while fur on the underside of their belly is slightly paler. Some musky rat-kangaroos have distinctive white markings on their throats that continue in a white line down to their chest.

Musky rat-kangaroos have small heads that are narrow and taper into a pointed snout. Their ears are small and rounded, and their tails are long, thin, and hairless, except for the area where the tail joins the body. The musky rat-kangaroo has four paws with five toes on each of its back feet and four on its front feet. Like other kangaroos, the middle toes have a fused (grown together) bone but separate claws. However, all other living kangaroos have only four toes on their back feet. The fifth toe of the musky rat-kangaroo does not have a claw. It is thought that this extra toe is used to help it climb.

Female musky rat-kangaroos have four nipples inside a forward-opening pouch where the young are carried after birth. Female and male musky rat-kangaroos are about the same size, although females usually weigh a little less than males. The average weight of a musky rat-kangaroo is between 11 and 24 ounces (337 to 680 grams).

GEOGRAPHIC RANGE

The musky rat-kangaroo lives only in a small area of Australian rainforest in northeastern Queensland.

HABITAT

Musky rat-kangaroos live on the rainforest floor. They usually prefer places where there are many plants that provide good cover for them. They often live near water, such as streams and lakes, because that is where the vegetation is more dense.

DIET

Musky rat-kangaroos are omnivores, meaning they eat both plants and animals. They eat small invertebrates such as insects and worms, as well as fruits, nuts, and roots. Musky rat-kangaroos find food by digging with their front paws in the ground and in the dead leaves and other plant material that cover the rainforest floor. When the musky rat-kangaroo eats, it often uses its front paws to hold the food and sits upright on its hind legs.

SAVING FOOD FOR LATER

Fruits from the rainforest are one of the most important parts of the musky rat-kangaroo's diet. However, these fruits are not easy to find during some parts of the year. The musky rat-kangaroo solves this problem by hiding food when there is an abundance of it, then finding it later when food is scarce. This hiding and finding is called scatterhoarding. Scatterhoarding helps ensure that the musky rat-kangaroo will not go hungry, even when food is scarce.

BEHAVIOR AND REPRODUCTION

Musky rat-kangaroos are diurnal, which means that they are active during the day. They are the only species in this order that is completely active during the day. At night musky rat-kangaroos sleep in nests. They also may return to their nests to keep cool during the hottest part of the day. To build their nests musky rat-kangaroos use their tails to pick up leaves and other items. They can curl their tails around what they want to hold and carry it back to their nests. This kind of flexible grasping tail is called a prehensile tail. They take the nest materials to clumps of vines or where two tree roots come together and make their nests there.

Instead of hopping on its two hind legs the way many other rat-kangaroos do, the musky rat-kangaroo moves by using all four legs. Consequently, its front and hind legs are kangaroos. Musky rat-kangaroos have been seen climbing trees, but little is known about why they do this.

Musky rat-kangaroos are thought to live and hunt for food primarily alone, although one scientist reported having seen up to three musky rat-kangaroos feeding in the same place. In the wild, they do not appear to be territorial, meaning that they do not defend an area that they consider to be theirs. When musky rat-kangaroos are kept in captivity, male/female relationships must be taken into consideration. Only one male can be kept in a cage at a time, but two females can be kept together. It is also possible for one male to share a space with more than one female. Little research has been done on how musky rat-kangaroos interact with each other.

Musky rat-kangaroos usually mate between February and July. They normally have two offspring at a time, although they sometimes have three. Like all marsupials, the young are born tiny, blind, hairless, and very immature. The young are not able to fend for themselves and must crawl over their mother's fur and into her pouch. In her pouch they attach themselves to a nipple and spend the next twenty-one weeks in the pouch as they grow and develop. After the young leave the pouch they usually spend time in the nest for another few weeks before they begin to leave the nest and follow their mother.

During the period of time in which a young musky rat-kangaroo follows its mother around the outside of the nest, it is known as a "young-at-foot" (sometimes also called a "young-at-heel"). It is not allowed to return to the pouch, although it is still allowed to suckle (nurse). The young continue to grow and mature, eventually leaving their mothers to go off on their own.

MUSKY RAT-KANGAROOS AND PEOPLE

The musky rat-kangaroo does not have any known particular significance to humans, except to the scientists who study them.

CONSERVATION STATUS

The musky rat-kangaroo not considered threatened in the wild. However, it is of concern to conservationists, because it lives only in a very small area of the rainforest in northeastern Queensland. Its habitat is disappearing because of clear cutting for agriculture. Because the musky rat-kangaroo lives in only one location, any severe loss of its habitat could be devastating to its population.

FOR MORE INFORMATION

Books:

Triggs, Barbara. Tracks, Scats and Other Traces: A Field Guide to Australian Mammals. Oxford, U.K.: Oxford University Press, 1996.

Woods, Samuel G. Sorting Out Mammals: Everything You Want to Know About Marsupials, Carnivores, Herbivores, and More! Woodbridge, CT: Blackbirch Marketing, 1999.

Web sites:

Chambers Wildlife Rainforest Lodges, Tropical North Queensland, Australia. "Musky rat kangaroo." http://rainforest-australia.com/rkangaroo.htm (accessed on June 30, 2004).

Other sources:

Berry, Ruth and Mark Chapman. ABC TV Documentaries: Hypsi: The Forest Gardener. Aired: 1/16/2001. http://www.abc.net.au/tv/documentaries/stories/s231600.htm (Web site accessed on June 30, 2004).