Koala

A Koala is a species of mammal known by the scientific name Phascolarctos cinereus. Due to the shape of their body and their fur, are often thought of as bears, which is a misconception. They are actually marsupials, which means that they raise their young in a pouch. Koalas only live in Australia, where they spend most of the time that they are awake eating leaves from the eucalyptus tree. These leaves would be poisonous to most animals, but the koala's special digestive system protects them from the toxins. The koala population is currently declining in some areas, so many people are trying to protect them and the trees that they inhabit.

Anatomy
The average koala weighs about twenty pounds and stands at about thirty inches high. Their entire body is covered with a fur coat, ranging in color from light gray to brown, with white patches on the neck, chest, and insides of the ears and arms. Male koalas have a brown spot in the middle of their chest, which is actually a special gland that excretes a substance they use to mark their territory. The coat is waterproof, keeping the koala both warm and dry. The coloring of the coat also acts as camouflage when they are hanging in trees. Female koalas have a pouch on their belly that carries the young while they are still developing.

Koalas have some very noticeable features on their head. They have a very large nose, which aids their sense of smell. This helps them differentiate between tree species, as well as tell if the leaves are poisonous. They also have very large ears, which most likely helps them cool off during hot summer days. Although their head is also relatively large compared to their body, the brain is not very big. It has been theorized that the koala's brain is smaller so that the koala can conserve more energy.

The koala's arms are uniquely suited for climbing. Each front paw has five fingers, two of which are opposable thumbs located on opposite sides of the paw. These thumbs, along with their sharp claws, make it very easy for the koala to grip branches as it climbs in search of food. Their hind paws are similar to their forepaws, except on the hind paws, the second and third toes are fused together to form a sort of "grooming claw". The muscles in their arms and legs are also very strong, allowing them to hang on tree branches for most of the time that they are awake. Their palms and soles are covered in rough pads, which offer excellent grip and protection from being damaged by rough tree branches. Koalas are the only known animal besides humans to have their own unique fingerprint.

There are some characteristics of koalas that can change depending on where they live. Koalas who live in Northern Australia are about two feet tall and weigh about fourteen pounds. They also usually have gray fur. Koalas who live in southern Australia tend to be much larger, usually about three feet high and weighing twenty-six pounds. They will also tend to have thicker, brown fur instead of gray. The larger size and thicker fur of the southern koalas is helpful to them in the cold winters of south Australia.

Reproduction
Koala mating season runs between August and February. First, the males begin to bellow loudly to pronounce their dominance and to attract females. Once a female chooses a male, they mate. About 35 days later, the female gives birth to a small joey, which weighs about 0.5 grams. The joey uses its keen senses of smell and its amazing climbing ability to crawl across the mother's fur into the pouch on her stomach. The joey then attaches to a nipple inside of the pouch that gives off milk that the joey will feed on for four to five months while it grows. During its time in the pouch, the joey will grow larger and develop fur, eyes, and other important features. At about 22 weeks, the joey finally opens it eyes and begins to poke its head out of the pouch. Over the course of the next couple of weeks, the koala will begin to come out of the pouch, and at 30 weeks, will remain outside of the pouch clinging to it's mothers stomach for all of the time that it is not sleeping. After this, the koala will begin to venture away from its mother, but not more than a meter at first. Then, as time passes, the joey will venture further and further from its mother. After about a year, the joey will be almost full grown, and will leave its mother to find its own living area.

Habitat
Koalas are native to Australia. They live in any area that contains the two they need to survive: Tree species that the koala can eat, usually eucalyptus, and other koalas. Because of this, koalas are always found in areas with eucalyptus trees, where other koalas will gather. In recent years, some habitats of koalas have been destroyed, leaving many koalas without trees to live in. Foundations such as the Australian Koala Foundation are trying to stop the destruction of the eucalyptus trees, but little of the land with the trees is protected, so not much can be done about it.

Diet
Nearly all of the koala's diet consists of leaves from the eucalyptus tree. The leaves are not very nutritious, though, being extremely fibrous and low in nutrients. Because of this, the koala has to consume between 200 to 500 grams of the leaves per day. However, the leaves are not only low in nutrition, they are also poisonous. Fortunately, the koala's digestive system is very well adapted to dealing with these problems. The koala digests food very slowly, and the digestive tract is very long, allowing the koala to absorb almost all of what little nutrition lies in the leaves. The digestive tract can also detoxify the poisons found in the leaves, making it safe for the koala to consume them. The leaves have a lot of water in them as well, so the koala rarely needs to drink except in times of drought.

Threats
Very few animals prey upon koalas, however, there are many other hazards that can hurt or kill them. The constant spread of human cities has encroached on koala habitats, introducing problems such as cars. The koala does not move very fast, making it very easy for one to be hit by a speeding car. Dogs and cats may also harm koalas. Humans also are constantly deforesting areas where the koalas live, destroying many of the trees that the koalas need to eat from. The dry environment in some of the koala's habitat can also cause many fires, which can kill koalas as well as destroy the trees that they eat from. Diseases also hurt many koalas. Chlamydia, a sexually transmitted disease, is a common disease among koalas, and can cause blindness, urinary tract infections, and reproductive tract infections. Chlamydia is not always a problem, but increased stress can cause an outbreak. Since a lot of the koala's trees are being destroyed, many koalas are stressed, and in small enough groups, chlamydia can be a serious problem.

Effects on the environment
In most areas inhabited by koalas, they are of little threat to the ecosystem since their numbers never grow too large. However, if koala populations rise too much, they can start to destroy the local plant life. In places such as Kangaroo Island, koalas thrive with little predation and an abundance of eucalyptus leaves. On Kangaroo Island, koala populations have risen to levels where they are beginning to destroy entire forests by eating all of the leaves, thereby killing the trees. Some people claim that the koalas are not the cause of the dying forests, but that doesn't seem likely since removing the koalas from the area is the only thing that revitalizes the trees. The Australian government has tried shipping out koalas or sterilizing males to reduce the populations, but since there are no serious threats against the koalas on Kangaroo Island, the populations continue to grow.