If asked to name an animal from Australia, you might say koala bear. Contrary to the popular name, koalas are not bears. They are tree-dwelling marsupials found in the forests of eastern Australia. Its brown fuzzy body, large black nose and tufted ears tend to win over anyone who sees a koala in person, but behind that cute face is a lean, mean, eucalyptus-eating machine. Koalas are highly specialized mammals with several unique physical adaptations that help them survive where most other animals cannot.
Their diet consists primarily of eucalyptus leaves, which are high in toxins and fiber and low in nutrition. Koalas have sharply pointed molars to mash leaves for easier digestion. Their stomach contains specialized bacteria to detoxify the leaves. The cecum, which is the first part of the large intestine, absorbs nutrients and is larger in plant-eating mammals. Compared to a horse's cecum, which is 4 feet long, the koala's 8-foot cecum is an adaptation developed to extract as much energy from each leaf as possible.
Koalas rarely leave the trees and their feet are highly adapted for climbing trunks and grasping branches. Each front paw has five digits, two of which are opposable like human thumbs. The hind feet each have five digits also, one being an opposable digit. The second and third digits are fused together to form one digit, which is used for grooming purposes. These adaptations give the koala a better grip. Long claws and padded feet also improve the koala's travels through the forest.
The koala's dense coat protects it from cold and heat extremes. Since koalas do not build nests or other types of shelters, the fur protects them from the elements, such as rain. Fur near the rump is extremely dense so that the koala is protected while sitting in trees.
The koala's nose appears relatively large for its head, but it's a necessary adaptation for detecting toxins in eucalyptus leaves. Koalas sniff leaves before eating them and their large nose provides a better assessment of the toxin levels in each leaf than a small nose could. Their sense of smell also helps koalas detect scent markings of other koalas.