Koala

The Koala (Phascolarctos cinereus) is a thickset arboreal marsupial herbivore native to Australia, and the only representative of its family, Phascolarctidae. more...

The koala's scientific name comes from the Greek: phaskolos meaning "pouch" and; arktos meaning "bear". The cinereus part is Latin and means "ash-coloured". Some people refer to the koala as a koala bear—this is technically incorrect, since koala is not part of the bear family. The word "koala" comes from an Aboriginal word meaning "does not drink".

Koalas are found all along the eastern coast of Australia from near Adelaide to the base of the Cape York Peninsula, and as far into the hinterland as there is enough rainfall to support suitable forest. The koalas of South Australia were exterminated during the early part of the 20th century, but the state has since been repopulated with Victorian stock.

Taxonomy and evolution

Although three subspecies have been described, these are arbitrary selections from a cline and are not generally accepted as valid. Following Bergmann's Rule, southern individuals from the cooler climates are larger. A typical Victorian koala (formerly P. cinereus victor, see illustrations) has longer, thicker fur, is a darker, softer grey, often with chocolate-brown highlights on the back and forearms, and has a more prominently light-coloured ventral side and fluffy white ear tufts. Typical weights are 12 kg for males and 8.5 kg for females. In tropical and sub-tropical Queensland, however, Koalas are smaller (at around 6.5 kg for an average male and just over 5 kg for an average female), a lighter, often rather scruffy, grey in colour, and have shorter, thinner fur. Queensland koalas were previously classified as the subspecies P. cinereus adustus, and the intermediate forms in New South Wales as P. cinereus cinereus. The variation from one form to another is continuous, and there are substantial differences between individual Koalas in any given region such as hair color.

Koala fossils are quite rare, but some have been found in northern Australia dating back 20 million years ago. During this time, the northern half of Australia was rainforest. They did not specialise in a diet of eucalyptus until the climate cooled and eucalyptus forests grew in the place of rainforests. Fossils prove that before 50,000 years ago, giant koalas inhabited the southern regions of Australia. The koala fills the same ecological role as the sloth of South America. Its origins are unclear. However, since its pouch opens backwards instead of forwards like most other marsupials, it is theorised that it may have evolved from a burrowing marsupial.

Physical description

Koalas are broadly similar in appearance to the wombat (their closest living relative), but have a thicker, softer coat, much larger ears, and longer limbs, which are equipped with large, sharp claws to assist with climbing. Weight varies from about 14 kg for a large, southern male, to about 5 kg for a small northern female. They are generally silent, but male koalas have a very loud advertising call (a nasal snort that human children delight in imitating) that can be heard from almost a kilometre away during the breeding season. There is little reliable information about the lifespan of koalas. However, in captivity they have been observed to reach the age of 15 years.

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