The Koala (Phascolarctos cinereus) is a thickset arboreal marsupial herbivore native to Australia, and the only extant representative of the family Phascolarctidae.
The Koala is found in coastal regions of eastern and southern Australia, from near Adelaide to the southern part of Cape York Peninsula. Populations also extend for considerable distances inland in regions with enough moisture to support suitable woodlands. The Koalas of South Australia were largely exterminated during the early part of the 20th century, but the state has since been repopulated with Victorian stock. The Koala is not found in Tasmania or Western Australia.
The word koala comes from Dharuk gula. Although the vowel /u/ was originally written in the Latin alphabet as “oo” (in spellings such as coola or koolah), it was changed to “oa” possibly due to an error. The word is erroneously said to mean “doesn’t drink”.The scientific name of the Koala’s genus, Phascolarctos, is derived from Greek phaskolos “pouch” and arktos “bear”. Its species name, cinereus, is Latin and means “ash-coloured”.
When first adopted by English speakers, the name Koala bear became popular, as this roughly evoked the species’ similarity in appearance to the Teddy bear, to people unfamiliar with it. Although taxonomically incorrect, the name Koala bear is still in use today outside Australia — its use is discouraged because of the inaccuracy in the name. Other descriptive English names based on “bear” have included monkey bear, native bear, and tree-bear.
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) 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 and New South Wales Koala weights are 12 kg (26 lb) for males and 8.5 kg (19 lb) for females. In tropical and sub-tropical Queensland, however, the Koala is smaller (at around 6.5 kg (14 lb) for an average male and just over 5 kg (11 lb) for an average female), a lighter often rather scruffy grey in colour, and has shorter, thinner fur. In Queensland the Koala was 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 colour. The origins of the Koala are unclear, although almost certainly they descended from terrestrial wombat-like animals. Koala fossils are quite rare, but some have been found in northern Australia dating to 20 million years ago. During this time, the northern half of Australia was rainforest. The Koala did not specialise in a diet of eucalypts until the climate cooled and eucalypt forests grew in the place of rainforests. The fossil record indicates 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.
The Koala is broadly similar in appearance to the wombat (their closest living relatives), but has a thicker coat, much larger ears and longer limbs. The Koala has large, sharp claws to assist with climbing tree trunks. Weight varies from about 14 kg (31 lb) for a large southern male, to about 5 kg (11 lb) for a small northern female. The Koala’s five fingers are arranged with opposable thumbs, providing better gripping ability. The first two fingers are positioned in apposition on the front paws, and the first three fingers for the hind paws. The Koala is one of the few mammals (other than primates) that has fingerprints. Koala fingerprints are similar to human fingerprints; even with an electron microscope, it can be quite difficult to distinguish between the two.
The teeth of the Koala are adapted to their herbivorous diet, and are similar to those of other diprotodont marsupials, such as kangaroos and wombats. They have sharp incisors to clip leaves at the front of the mouth, separated from the grinding cheek teeth by a wide diastema.
The male Koala, like many marsupials, has a bifurcated penis. The female has two lateral vaginae, a feature unique to the Koala, and it has two separate uteri which is common to all marsupials.
The brain in the ancestors of the modern Koala once filled the whole cranial cavity, but has become drastically reduced in the present species, a degeneration scientists suspects is an adaptation to a diet low in energy. One of the smallest in marsupials with no more than 0.2% of its body weight, about 40% of the cranial cavity is filled with cerebrospinal fluid, while the brain’s two cerebral hemispheres are like “a pair of shrivelled walnut halves on top of the brain stem, in contact neither with each other nor the bones of the skull. It is the only animal on Earth with such a strangely reduced brain.”
It is generally a silent animal, but males have a very loud advertising call that can be heard from almost a kilometre away during the breeding season. When under stress, Koalas may issue a loud cry, which has been reported as similar to that of a human baby. There is little reliable information about the lifespan of the Koala, but in captivity they have been observed to reach the age of 18 year.
The inverted thumbs on the Koala’s back feet help for grip while the Koala changes branches or eats with its front hands.
Females reach maturity at 2 to 3 years of age, males at 3 to 4 years. If healthy, a female Koala can produce one young each year for about 12 years. Gestation is 35 days. Twins are very rare; the world’s first confirmed identical twin Koalas, named “Euca” and “Lyptus“, were born at the University of Queensland in 1999. Mating normally occurs between December and March, the Southern Hemisphere’s summer.
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 that are disturbed are known to be violent, their teeth and claws capable of causing considerable injury to humans; special handling requirements are as such applicable.
The Koala was hunted almost to extinction in the early 20th century, largely for its fur. Millions of furs were traded to Europe and the United States, and the population has not fully recovered from such decimations. Extensive cullings occurred in Queensland in 1915, 1917 and again in 1919 when over one million Koalas were killed with guns, poisons and nooses. The public outcry over the cullings was most likely the first wide-scale environmental issue that rallied Australians. Despite the growing movement to protect native species, the drought of 1926–28 lead to the another 600,000 Koalas being killed during a one-month open season in August 1927.
Today, habitat loss and the impacts of irresponsible urbanisation (for example dog attacks and traffic accidents) are the leading threats to the survival of the Koala. In recent years, some colonies have been hard hit by disease, especially chlamydia. The Koala requires large areas of healthy, connected forest and will travel long distances along tree corridors in search of new territory and mates. The increasing human population of the coastal parts of the continent continues to cut these corridors by agricultural and residential development, forestry and road-building, marooning Koala colonies in decreasing areas of bush. The long term viability of the Koala is therefore threatened by genetic weakness. The Australian Koala Foundation has mapped 40,000 km2 (15,000 sq mi) of land for Koala habitat and claims it has strong evidence to suggest wild Koala populations are in serious decline throughout the species natural range. Although the species covers a large area, only ‘pieces’ of Koala habitat remain. These pieces need to be managed, protected and restored in a coordinated way. Presently, many habitats are lost to weeds, clearance for agriculture, or carved up by developers. Other threats come from logging, poor management, attacks from feral and domestic animals, diseases, and roads.
- Queensland — Common, or “Least Concern Wildlife” throughout the state, except in the relatively small South East Queensland Bioregion, where it is listed as Vulnerable.
- New South Wales — listed at a state scale as vulnerable, but varying regionally from “secure” to “locally extinct”.
- South Australia — classified as Rare.
- Victoria — The Koala population in Victoria is considered “large and thriving”.
The US government has declared the Koala a threatened species, however the Australian government has not. A review of the species national conservation status concluded that the Koala is not threatened at a national scale, with a population that numbers in the hundreds of thousands. This was the third review undertaken by the federal government that came to this conclusion. Other studies have estimated as few as 80,000 Koalas left in the wild, and the Australian Koala Foundation estimates there are around 100,000. The IUCN lists the species as “Lower Risk / Near Threatened”.
As with most native Australian animals, the Koala cannot legally be kept as a pet in Australia or elsewhere. The only people who are permitted to keep Koalas are wildlife carers and, occasionally, research scientists. These people are issued with special permits to care for Koalas, but have to return them to the wild when they are either well enough or, in the case of joeys, old enough.
From Wikipedia, the free encyclopedia.