Koala
July 13th, 2008
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.
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.
A baby Koala is referred to as a joey and is hairless, blind, and earless. At birth the joey, only a quarter of an inch long, crawls into the downward-facing pouch on the mother's belly (which is closed by a drawstring-like muscle that the mother can tighten at will) and attaches itself to one of the two teats. Young remain hidden in the pouch for about six months, only feeding on milk. During this time they grow ears, eyes, and fur. The joey then begins to explore outside of the pouch. At about this stage it begins to consume small quantities of the mother’s "pap" (formerly thought to be excrement, but now thought to come from the mother's caecum) in order to inoculate its gut with the microbes necessary to digest eucalypt leaves. The joey will remain with its mother for another six months or so, riding on her back, and feeding on both milk and eucalypt leaves until weaning is complete at about 12 months of age. Young females disperse to nearby areas at that time; young males often stay in the mother's home range until they are two or three years old.
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.
In contrast to the situation on much of the mainland, where populations are declining, the Koalas of many island and isolated populations have reached what some have described as 'plague' proportions. On Kangaroo Island in South Australia, Koalas introduced some 90 years ago have thrived in the absence of predators and competition. Combined with an inability to migrate to new areas, this has caused the Koala populations to become unsustainable and threaten the island's unique ecology. In particular, species of Manna Gum, native to the island, are being stripped by Koalas at a rate faster than they can regenerate, endangering local birds and invertebrates that rely on them, and causing the extinction of at least one isolated population of manna. Koala numbers are estimated at over 30,000, with ecologists suggesting that the island can sustain 10,000 at most. Although culling has been suggested as a means to reduce Koala numbers, with the South Australian government seriously considering such in 1996, this has met with fierce opposition both domestically and internationally, and the species remains protected. The popularity of the Koala has made the possibility of a cull politically improbable, with any negative perception likely to impact tourism and a government's electability. In place of a cull, sterilisation and translocation programs have had only limited success in reducing numbers thus far, and remain expensive. There is evidence that Koalas relocated to the mainland have difficulty establishing themselves in the different circumstances. A mooted alternative to the complex sterilisation method, wherein the animal must first be captured, are hormonal implants that can be injected via darts.
