Not bears, but marsupials
Koalas aren’t bears. They’re marsupials, meaning their young are born underdeveloped and then continue developing in the mother’s pouch.
Habitat loss is their biggest threat
Major threats include land clearing, bushfires, and diseases affecting eucalyptus trees (such as dieback).
Population estimates
Between 33,000 and 60,000 koalas likely remain in Australia.
Special paws
Koalas have five digits on each front paw. Two of these are opposable, which helps them grip branches and food.
On their hind paws, the 2nd and 3rd digits are fused, forming a grooming claw.
Sleeping a lot
Koalas sleep up to 18-20 hours per day. Their leaf-based diet is low in nutrition, so they conserve energy by resting a lot.
Eating habits
At night they eat about 0.5 to 1 kilogram (≈1-2 pounds) of eucalyptus leaves.
Eucalyptus leaves are toxic to most animals; koalas have a long cecum with bacteria to help detoxify the leaves.
“Home trees” and home range
Each koala has certain trees it returns to regularly (“home trees”). The collection of trees it uses is its “home range”. These ranges overlap with those of other koalas, but koalas tend not to venture into another’s home range unless they are breeding.
Male scent glands
Mature male koalas have a dark chest scent gland which they use to mark territory by rubbing on trees.
Joey development
Baby koalas are called “joeys”. When born, they are about 2 cm long, blind, furless, and their ears are undeveloped.
They crawl into the mother’s pouch, attach to a teat (which swells in their mouth to hold them in place) and stay there for about 6-7 months.
Before eating eucalyptus leaves, joeys eat “pap” — soft, runny droppings from their mother — to acquire the gut microbes necessary to digest the leaves.
After leaving the pouch, they may ride on their mother’s back and still suckle until they are too large. They often leave their mother’s home range between 1 and 3 years old.
Maturity
Females become sexually mature at about 2 years old, males around 3-4 years.
Geographic range and habitat
Koalas are found naturally only in eastern and southern parts of mainland Australia (Queensland, New South Wales, Victoria, South Australia) and certain nearby islands. They live in tall eucalyptus forests and woodlands, not in deserts or rainforests.
Moisture source
Koalas get most of their water from the eucalyptus leaves they eat, so they rarely need to drink. However, they will drink water especially when leaves have low moisture (e.g. during droughts).
Chlamydia
Many wild koala populations are infected with chlamydia. Usually it causes health problems when the koalas are stressed (by habitat loss, etc.).
Human-caused mortality
Cars and dogs kill significant numbers of koalas each year.
Legal protection of habitat is patchy; much of koala habitat is on private land and is not protected by legislation.
