Koala: Phascolarctidae

One reason that koalas can exist on low-nutrient food is that they have developed a lifestyle that allows them to conserve Koalas come out of their mother's pouch when they're about six months old, and cling to her belly or back until they are one year old. (© Kenneth W. Fink/Photo Researchers, Inc. Reproduced by permission.) energy. They sleep for up to twenty hours each day, and also spend part of the time that they are awake resting. They are nocturnal animals, feeding mainly at night.

Koalas live alone. Males use the scent gland on their chest to mark certain trees as their own territory. They will fight with other male koalas that come into their home trees. The male's home territory often overlaps with that of several females.

The size of the territory depends on how plentiful the food supply is.

Koalas mate during the cool season in Australia. A dominant male will mate with as many females as he can find. Once mating is complete, the animals go their separate ways, and the male has nothing to do with raising the offspring. Koalas are capable of mating when they are two years old, but generally do not begin to reproduce until they are four or five. Their lifespan is about ten years in the wild, and almost double that in captivity.

A single baby is born after a thirty-five–day pregnancy. The baby is tiny, measuring less than an inch (2 centimeters) and weighing less than 0.02 ounces (0.5 grams). The newborn crawls to its mother's pouch where it stays for five to seven months. When it is about half a year old, it comes out of the pouch and clings to its mother's belly or back. During this time, it still nurses, but it also eats vegetable material that has passed through the mother's digestive system. Scientists believe that in this way the bacteria in the cecum that is needed to digest eucalpytus leaves is passed on from mother to child. The young koala stays with its mother until it is about a year old. By age two it begins looking for its own territory.