Australia is a land of many wonders. The scenery is breathtaking and the animals are as diverse as they are unusual. It is home to some of the most deadly animals on the planet, but also several of the most adorable. One of these is the Koala Bear. Unlike their common name, however, the Koala Bear is not a bear. It is a marsupial, meaning that their young are born immaturely developed and develop fully in a pouch before emerging into the world.
The Koala is also one of the only creatures on earth that exists solely on the leaves of the eucalyptus tree. This is a most unusual trait as almost all other animals have a varied diet whether they are herbivores, carnivores, or omnivores. In fact, to most other animals eucalyptus leaves are poisonous. Since eucalyptus leaves are very fibrous and have very little nutritional value, in response they have also developed an abnormally low metabolic rate. This way the eucalyptus leaves stay in their digestive system for much longer than it would with any other animal and allows for more complete digestion and absorption of the most nutrients possible. This also means that the koala is not a very active creature since their metabolic rate doesn't allow for much strenuous activity. Koalas can spend as many as 22 hours a day sleeping in order to conserve energy and allow for digestion
Another adaptation that koalas have is an organ called a caecum. This is an organ in the digestive system that is specifically designed to digest fibrous materials. Humans also have a caecum, but the koala's is much longer due to their fiber-rich diet. Even this digestive adaptation only allows for around 25% of the fiber in a eucalyptus leaf to be digested. But the caecum also assists in extracting water from the leaves, allowing koalas to drink from other sources very rarely. A third adaptation in response to their diet is the ability to filter out toxins in the eucalyptus leaves. Since eucalyptus is poisonous the koala evolved to be able to filter those toxins out. It has been noted that some eucalyptus trees are more toxic than others, usually in correlation with where the tree grows. Trees in fertile areas seem to be less toxic than trees in areas where the soil quality is poor. This may help to explain why koalas have "home trees" where they spend most of their time and will not as readily eat leaves from other trees in surrounding areas. While their main source of nutrition is eucalyptus, koalas will occasionally branch out and browse on the leaves of other trees like the wattle tree or tea tree.
The social behavior of koalas is very complex and structured. Koalas are nocturnal, meaning that they are active during the night and sleep during daylight hours. All koalas have what is called a "home range". Within their home range they do not live with other koalas regularly, although their home range may overlap with several other animals in the area. The largest home ranges are the territory of the dominant males in the region. His region will overlap with most of the females in the area and perhaps a few of the less dominant males. Since koalas are highly territorial, it would not be unusual for a koala to "visit" the other animals in his home range on a daily basis during breeding season, both for breeding or establishing dominance of the territory. In that region, although the animals all live separately and in neighboring areas, it is one large stable breeding area. That breeding group will remain the same for as long as the territory stays the same.
A home range for a koala can vary in size and is dependent on the availability of space. If an intrusion is made on that area then the home ranges will be smaller than in an uninhabited expanse of land. Each koala has specific trees in its range that are for food, others that are for shelter, and still others that are used for socializing. The trees used for socializing are normally on the very fringes of their home range where the ranges are most likely to overlap. That home range will be the home of that particular koala for the entirety of its life. Even after a koala has died it normally will be around a year before another koala takes over the territory.
A koala will stay with its mother until it becomes sexually mature. At that time the young koala will have to leave the territory and find unclaimed territory somewhere else, preferably with a new breeding group. At any given time there are also transient animals that linger temporarily on the outskirts of a territory for a length of time before moving on. Usually these transient animals are young males that are trying to establish their own breeding territory.
Koalas can communicate over large distances with vocalizations. Males will often make a bellowing sound to establish that their are the dominant male in the area. This vocalization is made to avoid confrontation with other male koalas by establishing dominance without expending too much energy. Females can also bellow but don't do so as often as the males, since they largely have less of a need to make a dominant stance. Mother koalas and their young will coo or murmur to each other often as a bonding mechanism. All koalas (male and female) share a similar cry of fear, a cry similar to the sound of a human baby crying.
Koalas are just another of the diverse and fascinating animals that inhabits the continent of Australia. They are different from any other animals on earth in many different ways, and yet we still cannot stop ourselves from wanting to learn more about them. They are a complex animal that maintains a delicate balancing act in an ever more developed world that is threatening to encroach on their habitat.