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Phascolarctos cinereus [fas kO' lark tuhs sin Er' E ush]
The koala averages 27-36 inches in length and 9-20 pounds in weight; females are slightly smaller than males, and southern koalas are about 30 percent larger than northern koalas. It has soft, wool-like fur that is gray above and white below, with a white "beard" and long white hairs on the tips of the ears.
Well adapted to life in the trees, the koala has a lean body, long, muscular front and hind limbs and large, sharp claws to help with gripping tree trunks, and rough skin on the bottom of its feet to provide friction good for climbing. It also has five digits on its front paws, two of which are opposable (this would be like a human having two thumbs), an adaptation that allows the koala to grip branches as its moves from tree to tree. Its hind paws have one opposable digit with no claw, again for grip, and its second and third digits are fused into one double claw the animal uses for grooming purposes. Its fur is thicker on its rump to provide a cushion when sitting on branches.
Distribution and Habitat
The "poster child" for Australian wildlife, the koala was once found throughout the island continent but its range is now primarily restricted to the states of Queensland, New South Wales, Victoria, and South Australia. It lives in eucalyptus forests and low woodlands.
Koalas feed on leaves and bark from twelve different species of eucalyptus, as well as mistletoe and box leaves. All of these plants are toxic to most mammals, but the koala's digestive system is specially adapted to detoxify the poisonous chemicals in the leaves. In fact, koalas are the only known mammals other than the Greater Glider and Ringtail Possum that can feed on eucalyptus. A fully grown koala can consume up to 2-1/2 pounds of leaves a day. Because eucalyptus leaves have a high moisture content koalas rarely need to drink water.
Koalas breed once a year. The gestation period is about 35 days, after which a single inch-long, blind, furless, and earless joey is born. Immediately after being born, it crawls up from the birth canal into the mother's pouch, where it attaches itself to one of two teats. While most marsupials have pouches that open upward, toward their heads, the koala's pouch opens out toward her hind legs. The joey will stay in its mother's pouch until about six months of age, after which it rides on her back until about a year old. If the mother has bred again, the joey will leave its mother at about one year of age; if she hasn't, it may stay with her until reaching sexual maturity, which takes 2-3 years. A koala can live up to 17 years in the wild.
Koalas live in well-defined home ranges. Each home range is often controlled by a single alpha male, with a number of females also living inside that area. These females will mate almost exclusively with the dominant male, who will defend his territory against outside males that may move into the area. Individual koalas only come together for mating.
Although it looks somewhat like a small bear, the koala's closest living relative is the wombat.
Fossils of koala-like animals have been found dating all the way back to 25-40 million years.
Koalas are one of the few mammals apart from primates to have fingerprints. Koala fingerprints so closely resemble human fingerprints that it can be hard to distinguish between the two.
The koala only has 11 pairs of ribs, while most mammals have 13.
In keeping with its low-energy lifestyle, the koala has a lower body temperature than other animals its size -- about 97.9 degrees F. By comparison, healthy temperature for domestic cats and dogs ranges from 100 to 102.5 degrees F.
There are fewer than 100,000 koalas left in the wild. Most of the koala's decline is attributed to habitat loss, but domestic dogs have also taken their toll.
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This page was last updated on August 31, 2018.