Mammals: Koala

Range: southeastern and eastern Australia Habitat: scrubland eucalyptus forest

Cuddly koalas

Have you ever heard someone refer to a koala as a "koala bear?" Well, like bears they are mammals, and they have round, fuzzy ears and look cute and cuddly, like a teddy bear. But koalas are not bears. They are members of a group of pouched animals called marsupials. Marsupials include kangaroos, wallabies, wallaroos, wombats, possums, and opossums. Many kinds of marsupials are native to Australia. Koalas look soft but their fur actually feels like the wool on a sheep. They also seem cuddly, but they are wild animals and don't make good pets.

Do all marsupials have pouches?

Female marsupials have pouches in which they carry their babies. Many marsupials, like kangaroos, have pouches that open upward, toward their heads. But koalas have pouches that open toward their hind legs. This adaptation keeps burrowing marsupials like wombats, which are close relatives of koalas, from getting dirt in their pouches when they dig. Although prehistoric koalas eventually stopped burrowing and started living in trees, they still have the primitive, back-facing pouch.

Born to climb

A koala, like other marsupials, begins life in a very unusual way. When it is born, it is only about the size of a large jelly bean and is not yet fully developed. In fact, a newborn koala, called a joey, can't even see or hear, but it sure can climb! Soon after the joey is born, it uses strong forelimbs and hands to crawl from the birth canal into its mother's pouch. In this warm, safe place the joey attaches to one of two nipples, drinks milk, and grows during the next six months. Even after it starts leaving the pouch, a joey will return to the pouch when it wants to hide or sleep. Sometimes it will ride on its mother's belly. After it grows too large for the pouch, the joey climbs onto its mother's back and holds on with strong hands and feet. After about a year, it can live alone in the trees.

To help it climb, a koala has special hands and feet, both of which have claws. A koala has two thumbs on its hands, and the ridged skin on the bottom of its feet gives it traction for climbing. Strong arm and shoulder muscles help a koala climb 150 feet (46 meters) to the top of a tree, and enable it to leap from treetop to treetop.

Why trees?

Koalas are basically slow-moving animals that need to sleep a lot and take a long time to digest their food. Being on the ground all the time would be a disadvantage, because predators could catch them easily. So instead they adapted to live way up in eucalyptus trees, their behinds firmly planted in the forks of branches, so they can chew leaves and nap all they want without feeling threatened. But they do travel on the ground, as well, to get from tree to tree or to a new area.

Catering to koalas

Koalas only eat eucalyptus leaves. Eating leaves from one kind of plant may seem boring, but there are more than 600 different kinds of eucalyptus trees and, from a koala’s point of view, each looks and tastes very different! Koalas prefer the leaves of about three dozen varieties. Joeys learn to eat eucalyptus leaves on their own gradually. At first the joey goes after leaves with its mouth. Its early attempts look like a game of bobbing for apples, with its nose getting in the way and pushing the leaves out of reach! Fortunately, joeys keep trying until they are successful. Eventually they figure out how to grab leaves with their front paws and put them in their mouths.

At the San Diego Zoo, koalas are offered fresh branches from several kinds of eucalyptus trees each day. These picky eaters can then select their favorite varieties. Koalas eat 1 to 1.5 pounds (454 to 680 grams) of leaves each day. Eucalyptus leaves are poisonous to most animals, but koalas have special bacteria in their stomachs that break down the toxic oils. Special cheek teeth grind the tough eucalyptus leaves. Koalas don't get many calories from their diet, but they conserve energy by moving slowly and by sleeping as much as 20 hours each day. Just because they sleep a lot does not mean they are quiet, boring animals. Keepers at the Zoo say that each koala has a unique personality. Koalas make several different vocalizations, from snores to bellows to screams.

First class, please!

The San Diego Zoo sends koalas all over the world for temporary loans. To make sure the traveling koala will be comfortable, a keeper travels with it to its new home and stays with it until it settles in. These furry travelers are so important they don't get checked into the baggage hold—actually they often travel first class. If eucalyptus does not grow well on the grounds of the koala's new zoo home, fresh eucalyptus branches are shipped to them twice a week. These koala loans allow thousands of people to observe and enjoy these unique marsupials. Koalas in the wild benefit from the loan program, too. Funds from this program are donated to koala habitat conservation in Australia.

The future of koalas

Koalas have few natural predators, although sometimes a dingo or large owl can take one. The most common direct causes of koala deaths are from motor vehicles and dogs. So they are definitely safest high up in trees. In the past, koalas were killed for their coats. In fact, from 1919 to 1924 eight million koalas were killed. Today, the koala is threatened by predation by domestic dogs and by a disease that has spread through most of the population. Unfortunately, some koalas get run over by cars. But the one thing that koalas and other wildlife can’t protect themselves against is the loss of their habitat. A combination of cooperative captive propagation programs, research, and support for habitat conservation projects continue to ensure the survival of koalas.