Koala Facts - Phascolarctos cinereus

Koalas are Under Threat by Disease, Fires, Land Development and Dogs

Oct 1, 2009

The koala is a small nocturnal marsupial that lives in eucalyptus trees along the south-eastern coast of Australia.

Koalas are marsupials, not bears and are gray in color with large white tuffed ears, black noses and a paler underbelly. Their thick wooly coat covers a thickset body and strong limbs for climbing and staying in trees. Their claws are very sharp and used for climbing and fighting.

Koalas tend to move around slowly but can race up to the top of a tree using its strong limbs and claws to grip. Koalas are basically nocturnal and spend 2-4 hours during the night feeding, than sleep for the rest of the day. Current Taxonomy of the Koala:

The Koala’s Diet

The koala’s diet is almost exclusively eucalyptus leaves, often called ‘gum leaves’, and this is where they get most of their water from also. Joeys have their first solid meal from the mother’s droppings that is converted to a substance called ‘pap’ after lactation ends. This 'pap' contains microbes to aid in food digestion.

Koalas, as with all herbivores, have much longer intestines than carnivores. Because vegetation is harder to digest than meat due to the cell walls of vegetation, herbivores have evolved longer intestines to enhance the processing of fibrous protein-poor food, such as eucalyptus leaves.

Koalas chew eucalyptus leaves into small pieces, which increases the amount of digestive juices the leaves are exposed too. The koala has the longest cecum (2 meters) of any animal of equivalent size. And the word koala is Aboriginal for ‘no water’.

Sexual Behaviour and Mating of the Koala

Koalas are solitary animals and while territories of males and females may overlap, males tend to steer clear of other males. Male koalas mark out territories using strong scent and make loud calls to deter other males. They will attack intruders savagely, particularly during mating season.

During breeding season male koalas will attempt to guard several female territories. Koalas mate at night and make loud noises during this time, which have been known to frighten campers who have heard them. Mating season for the koala is from December through to March.

Koalas reach sexual maturity at 2 years of age; however, they often don’t breed until 5 years of age, particularly the males. Gestation lasts from 25-35 days and one joey is born every year. The newborn will spend approximately 6 months in the mother's pouch after which it will climb onto the mother’s back in a piggy-back position and stay there for another 2-3 months. Koalas grow to around 60-85 cm (24-34in) and weigh in at 4-15kg (8.8-33lb). Lifespan for a koala is around 20 years.

Chlamydiosis in Koalas

In addition to the threats koalas face including dog attacks, fires, car accidents and developments, the virus chlamydiosis is threatening to wipe them out, already affecting 50-90% of the population. Stress brought on by other factors, in particular, humans moving into the regions where koala habitats are, is causing the virus to flare up resulting in sores, similar to cold sores.

These sores can lead to infections of the eye, urinary tract, reproductive and respiratory systems resulting in blindness, infertility and death. The Australian Koala Foundation is urging governments to classify koalas as a threatened species and to implement protection policies. Recently, a group of protesters left 5 dead koalas at the front of Queensland’s parliament house and since then, the Queensland government announced that it would protect koala habitats at Alexandra Hills, Queensland and is implementing protection policies.

Campbell and Reece, 2002, 'Animal Nutrition', in Biology 6th edition, ed. Benjamin Cummings, San Francisco, chap 41.

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