Behavior
The koala lives almost entirely on eucalypt leaves.
This is likely to be an evolutionary adaptation that takes advantage of an otherwise unfilled ecological niche, since eucalypt leaves are low in protein, high in indigestible substances, and contain phenolic and terpene compounds that are toxic to most species.
Like wombats and sloths, the koala has a very low metabolic rate for a mammal and rests motionless for about 16 to 18 hours a day, sleeping most of that time.
Koalas can be aggressive towards each other, throwing a foreleg around their opponent and biting, though most aggressive behavior is brief squabbles.
Handling koalas may cause them stress, and the issue of aggression and stress from handling is a political issue in Australia.
Koalas spend about three of their five active hours eating.
Feeding occurs at any time of day, but usually at night. Koalas eat an average of 500 g (18 oz) of eucalypt leaves each day, chewing them with powerful jaws to a very fine paste before swallowing.
The liver deactivates the toxic components ready for excretion, and the hind gut (especially the cecum) is greatly enlarged to extract the maximum amount of nutrient from the poor quality diet.
Much of this is done through bacterial fermentation: while young are being weaned, the mother passes these essential digestive aids on to her offspring.
The koala will eat the leaves of a wide range of eucalypts, and occasionally even some non-eucalypt species such as Acacia, Leptospermum, and Melaleuca.
It has firm preferences for particular varieties of eucalypt and these preferences vary from one region to another: in the south Manna Gum, Blue Gum, and Swamp Gum are favoured;
Grey Gum and Tallowwood are important in the north, and the ubiquitous River Red Gum of the isolated seasonal swamps and watercourses that meander across the dry inland plains allows the koala to live in surprisingly arid areas.
Many factors determine which of the 680 species of eucalypt trees the koala eats.
Among trees of their favourite species, however, the major factor that determines which individual trees the koala chooses is the concentration of a group of phenolic toxins called formylated phloroglucinol compounds.
Koalas are mainly nocturnal animals, which means they are more active at night.
The air is cooler at this time, so koalas lose less valuable moisture than they would during hot daylight hours.
Moving around is also less tiring when it is cooler.
Koalas spend eighteen to twenty hours each day resting and sleeping in trees.
They only come to the ground when moving from one tree to another.
When they are not sleeping, koalas are often eating.
They spend less than one percent of their day in other activities, such as grooming, traveling between trees, or finding a mate.
In cool weather, the Koala sleeps curled into a tight ball, to keep in body warmth.
In hot weather it lies draped over a branch, to let a cooling breeze blow around its legs and body. Koalas do not sweat, but they may lick themselves. As the spit dries.
It draws heat from the body – in same way that our sweat keeps us cool
During the day, the koala wakes occasionally to groom its fur or change position.
In hot weather it moves into the shade. On cool days it looks for a sunny, warm branch.
If necessary for an escape, koalas are good swimmers too. But if they smell trouble, they will always climb up the closest tree.
This is where they are safest.
Koalas are not very social animals.
They do not live together in groups or families. Koalas prefer to live alone. They are seldom friendly to one another.
Several koalas may live in the same area, but they will not socialize, or hang out together.
If more than one ends up in the same tree, they will avoid each other and stay on separate branches.
Mothers and babies are the only koalas that spend much time together.
Koalas make sounds and gesture to show how they feel. Even though they may look calm and cuddly, koalas can be noisy and nasty.
Angry koalas often scratch or bite anyone or anything that bothers them.
When a koala is hurt or feels afraid, it lets out a wail that sounds like a crying baby.
If you try touching a wild koala, it may scream.
Male koalas sometimes make a bellowing sound to attract females.