(pink – introduced)
The koala (Phascolarctos cinereus) is an arboreal herbivorous marsupial native to Australia, and the only extant representative of the family Phascolarctidae. It is classified in the suborder Vombatiformes within the order Diprotodontia, and its closest living relatives are the wombats. The koala is found in coastal areas of the continent's eastern and southern regions, inhabiting Queensland, New South Wales, Victoria and South Australia. It is easily recognisable by its stout, tailless body, round, fluffy ears and large, spoon-shaped nose. It is popularly known as the koala bear because of its bear-like appearance. The koala has a body length of 60–85 cm (24–33 in) and weighs 4–15 kg (9–33 lb). Pelage colour ranges from silver grey to chocolate brown. Koalas from the northern populations are typically smaller and lighter in colour than their counterparts in the more southern populations. It is possible that these variations are separate subspecies, but this is disputed.
Koalas typically inhabit open Eucalyptus woodlands, and the leaves of these trees make up most of their diet. Because this eucalypt diet provides them with only low nutrition and energy, koalas are largely sedentary and sleep for up to 20 hours a day. They are asocial animals, and bonding only exists between mothers and dependent offspring. Adult males communicate with loud bellows that intimidate rivals and attract mates. Males mark their presence with secretions from their chest glands. Being marsupials, koalas give birth to underdeveloped young that crawl into their mothers' pouches, where they stay for the first six to seven months of their life. These young koalas are known as joeys, and are fully weaned at around a year.
Koalas are listed as of Least Concern by the International Union for Conservation of Nature. The Australian government, however, lists populations in Queensland and New South Wales as Vulnerable. The biggest threat to their existence is habitat destruction due to agriculture and urbanisation. Because of its distinctive appearance, the koala is recognised worldwide as an iconic symbol of Australia.
The word koala comes from the Dharug gula. Although the vowel 'u' was originally written in the English orthography as "oo" (in spellings such as coola or koolah), it was changed to "oa", possibly in error. The word is mistakenly said to mean "doesn't drink". Because of the koala's resemblance to a bear, it was often miscalled the koala bear, particularly by early settlers. Other names like monkey bear, native bear, and tree-bear have also been used. Indigenous names include cullawine, koolawong, colah, karbor, colo, coolbun, boorabee, burroor, bangaroo, pucawan, banjorah, and burrenbong; many of these mean "no drink". The koala's genus name, Phascolarctos, is derived from Greek phaskolos "pouch" and arktos "bear". Its specific name, cinereus, is Latin for "ash coloured".
Taxonomy and evolution
|Phylogeny of Diprotodontia, (with outgroup)|
The koala was given its genus name Phascolarctos in 1816 by French zoologist Henri Marie Ducrotay de Blainville, who would not give it a specific name until further review. A year later, German zoologist Georg August Goldfuss gave it the binomial Lipurus cinereus. Because Phascolarctos was published first, according to the International Code of Zoological Nomenclature, it has priority as the official name of the genus. The koala is classified with wombats (family Vombatidae) and several extinct families (including marsupial tapirs, marsupial lions and giant wombats) in the suborder Vombatiformes within the order Diprotodontia. Vombatiformes is a sister group to a clade that includes macropods (kangaroos and wallabies) and possums. The ancestors of vombatiforms were likely arboreal, and the koala's lineage was possibly the first to branch off around 57 million years ago during the Oligocene.
The modern koala is the only extant member of Phascolarctidae, a family that once included several genera and species. During the Oligocene and Miocene, koalas lived in rainforests and had less specialised diets. Some species, such as the Riversleigh rainforest koala (Nimiokoala greystanesi) and some species of Perikoala, were around the same size as the modern koala, while others, such as species of Litokoala, were one-half to two-thirds its size. During the Miocene, the Australian continent began drying out, leading to the decline of rainforests and the spread of open Eucalyptus woodlands. The genus Phascolarctos split from Litokoala in the late Miocene and had several adaptations that allowed it to live on a specialised eucalyptus diet: a shifting of the palate towards the front of the skull; larger molars and premolars (causing the teeth to move downwards within the head); smaller pterygoid fossa; and a larger gap between the molar and the incisor teeth.
During the Pliocene and Pleistocene, when Australia experienced changes in climate and vegetation, koala species grew larger. Phascolarctos cinereus may have emerged as a dwarf form of P. stirtoni known as the giant koala. The reduction in the size of large mammals has been seen as a common phenomenon worldwide during the late Pleistocene, and it is traditionally believed that several Australian mammals, including the agile wallaby and the grey kangaroo, resulted from this dwarfing. However, a 2008 study questions this hypothesis, noting that P. cinereus and P. stirtoni were sympatric during the middle to late Pleistocene, and possibly as early as the Pliocene. The fossil record of the modern koala extends back at least to the middle Pleistocene.
Genetics and variations
Traditionally, three different subspecies have been recognised: the Queensland koala (P. cinereus adustus, Thomas 1923), the New South Wales koala (P. c. cinereus, Goldfuss 1817) and the Victorian koala (P. c. victor, Troughton 1835). These forms are distinguished by pelage colour and thickness, size and skull shape. The Queensland koala is the smallest of the three, with shorter, silver fur and a shorter skull. The Victorian koala is the largest, with shaggier, brown fur and a wider skull. The boundaries of these variations are based merely on state borders, and their status as subspecies are disputed. A 1999 genetic study suggests that the variations are simply differentiated populations. The study also found that there is limited gene flow between the populations. Other studies have found that koala populations have high levels of inbreeding and low genetic variation. Such low genetic diversity may have been a characteristic of koala populations since the late Pleistocene. The first sequencing of the genome was announced on 9 April, 2013 by a team of scientists from the Queensland University of Technology led by professor of microbiology Peter Timms.
The koala is a stocky animal with a large head and vestigial or non-existent tail. It has a full body length of 60–85 cm (24–33 in) and a weight of 4–15 kg (9–33 lb), making it the largest arboreal marsupial. Koalas from Victoria have twice the bodyweight of those from Queensland. The species is sexually dimorphic, with males 50% larger than females. Males are further distinguished from females by their more curved noses and the presence of chest glands, which are visible as hairless patches. As in most marsupials, the male koala has a bifurcated penis, and the female has two lateral vaginas and two separate uteri. The male's penile sheath contains naturally occurring bacteria that play an important role in fertilisation. The female's pouch opening is tightened by a sphincter that keeps the young from falling out.
The pelage of the koala is thicker and longer on the back, and shorter on the belly. The ears have thick fur on both the inside and outside. The back fur colour varies from light grey to chocolate brown. The belly fur is whitish; on the rump it is dappled whitish, and darker at the back. The koala has the most effective insulating back fur of any marsupial and is highly resilient to wind and rain, while the belly fur can reflect solar radiation. The koala has a cartilaginous pad at the end of the spine that may serve to make it more comfortable to sit in tree forks. Koalas have curved, sharp claws and powerful forelimbs, both good adaptations for arboreal life. The large forepaws have two opposable digits (the first and second, which are opposable to the other three) that allow them to grasp small branches. On the hindpaws, the second and third digits are fused, a typical condition for members of Diprotodontia, and the attached claws (which are still separate) are used for grooming. As in humans and other primates, koalas have friction ridges on their paws.
The koala has several adaptations for its eucalypt diet, which is of low nutritive value, of high toxicity, and high in dietary fibre. The animal's dentition consists of the incisors and cheek teeth (a single premolar and four molars on each jaw), which are separated by a large gap (a characteristic feature of herbivorous mammals). The incisors are used for grasping leaves, which are then passed to the premolars to be snipped at the petiole before being passed to the highly cusped molars, where they are shredded into small pieces. The partially worn molars of middle-aged koalas are optimal for breaking the leaves into small particles, resulting in more efficient stomach digestion and nutrient absorption in the small intestine. Koalas may also store food in their cheek pouches before it is ready to be chewed. After chewing, the food passes through the relatively small stomach and into the small intestine, which digests the eucalyptus leaves to provide most of the animal's energy. A koala sometimes regurgitates the food into the mouth to be chewed a second time.
Unlike kangaroos and eucalyptus-eating possums, koalas are hindgut fermenters, and their digestive retention can last for up to 100 hours in the wild, or up to 200 hours in captivity. Koalas can select which food particles to retain for longer fermentation and which to pass through. Large particles typically pass through more quickly, as they would take more time to digest. While the hindgut is proportionally larger in the koala than in other herbivores, only 10% of the animal's energy is obtained from fermentation. Since the koala gains a low amount of energy from its diet, its metabolic rate is half that of a typical mammal, although this can vary between seasons and sexes. The koala conserves water by passing relatively dry faeces high in undigested fibre, and by storing water in the caecum.
The koala has possibly the smallest brain in proportion to body weight of any mammal, being 60% smaller than that of a typical diprotodont. The brain's surface is fairly smooth, typical for a "primitive" animal. It occupies only 61% of the cranial cavity and is pressed against the inside surface by cerebrospinal fluid. The function of this amount of fluid is not known, although one possibility is that it acts as a shock absorber, cushioning the brain if the animal falls from its tree. The koala's small brain size is possibly due to the lack of sufficient energy to sustain a larger brain. As a result of its small brain, the koala has a limited ability to perform complex, unfamiliar behaviours. For example, when presented with plucked leaves on a flat surface, the animal cannot adapt to the change in its normal feeding routine and will not eat the leaves. The koala's olfactory senses are normal, and it is known to sniff the oils of individual branchlets to assess their edibility. Its nose is fairly large and covered in leathery skin. Its round ears provide it with good hearing and it has a well-developed middle ear. A koala's vision is not well developed, and its relatively small eyes are unusual among marsupials in that the pupils have vertical slits.
Ecology and behaviour
The koala's geographic range covers roughly 1,000,000 square kilometres (390,000 sq mi), and 30 ecoregions. It extends throughout eastern and southeastern Australia, encompassing northeastern, central and southeastern Queensland, eastern New South Wales, Victoria and southeastern South Australia. The koala was introduced near Adelaide and on several islands, including Kangaroo Island and French Island. The population on Magnetic Island represents the northern limit of their range. Fossil evidence shows that the koala's range stretched as far west as southwestern Western Australia during the late Pleistocene. In Queensland, koalas are unevenly distributed with the exception of the southeast. In New South Wales, they are abundant only in Pilliga, while in Victoria they are common nearly everywhere. In South Australia, koalas were extirpated by 1920 and subsequently re-introduced. Koalas can be found in habitats ranging from open forests to woodlands, and in climates ranging from tropical to cool temperate. In semi-arid climates, they prefer riparian habitats, where nearby streams and creeks provide refuge during times of drought and extreme heat.
Foraging and activities
Koalas are herbivorous, and while most of their diet consists of eucalypt leaves, they can be found in other tree genera, such as Acacia, Allocasuarina, Callitris, Leptospermum and Melaleuca. Although the foliage of over 600 species of Eucalyptus is available, the koala only shows a strong preference for around 30. They tend to choose species that have a high protein content and low proportions of fibre and lignin. The most favoured species are Eucalyptus microcorys, E. tereticornis, and E. camaldulensis, which, on average, make up more than 20 percent of their diet. Despite its reputation as a fussy eater, the koala is more generalist than other marsupial species, like the greater glider. Since eucalypt leaves have a high water content, the koala does not need to drink often; its daily water turnover rate ranges from 71 to 91 millilitres per kilogramme of body weight. Although females can meet their water requirements from eating leaves, larger males require additional water found on the ground or in tree hollows. When feeding, a koala holds onto a branch with hindpaws and one forepaw while the other forepaw grasps foliage. Small koalas can move close to the end of a branch, but larger ones stay near the thicker bases.
Because they get so little energy from their diet, koalas limit their energy use and sleep 20 hours a day; only 4 minutes a day are spent in active movement. They are predominantly active at night and spend most of their waking hours feeding. They typically eat and sleep in the same tree, possibly for as long as a day. On warm days, a koala may rest with its back against a branch or lie on its stomach or back with its limbs dangling. During cold, wet periods, it curls itself into a tight ball to conserve energy (it also abstains from eating during this time). On windy days, a koala will find a lower, thicker branch to rest on. While it spends most of the time in the tree, the animal will descend to the ground to move to another tree, walking all fours. The koala usually grooms itself with its hind paws, but sometimes uses its forepaws or mouth.
Koalas are asocial animals and spend just 15 minutes a day on social behaviours. In Victoria, home ranges are small and have extensive overlap, while in central Queensland they are larger and overlap less. Koala society appears to consist of "residents" and "transients", the former being mostly adult females and the latter male. Resident males appear to be territorial and dominate others with their larger body size, but they do not appear to have any reproductive advantage. Adult males occasionally venture outside their home ranges; when they do so, dominant ones retain their status. When a male enters a new tree, he marks it by rubbing his chest gland against the trunk or a branch; males have occasionally been observed to dribble urine on the trunk. This scent-marking behaviour probably serves as communication, and individuals are known to sniff the base of a tree before climbing. Scent marking is known to occur during aggressive encounters. Chest gland secretions are complex chemical mixtures—about 40 compounds were identified in one analysis—that vary in composition and concentration with the season and the age of the individual.
Adult males communicate with loud bellows – low pitched sounds that consist of snore-like inhalations and resonant exhalations that sound like growls. Because of their low frequency, these bellows can travel far though air and vegetation. Koalas may bellow at any time of the year, particularly during the breeding season, when it serves to attract females and possibly intimidate other males. They also bellow to advertise their presence to their neighbours when they enter a new tree. These sounds signal the male's actual body size as well as exaggerate it; females pay more attention to bellows that originate from larger males. Female koalas bellow, though more softly, in addition to making snarls, wails and screams. These calls are produced when in distress and when making defensive threats. Young koalas squeak when in distress. As they get older, the squeak develops into a "squawk" that is produced both when in distress and to show aggression. When climbed over by a conspecific, a koala makes a low grunt with its mouth closed. Koalas make numerous facial expressions. When snarling, wailing or squawking, the animal curls the upper lip and points its ears forward. During screams, the lips retract and the ears are drawn back. Females bring the lips forward and raise their ears when agitated.
Agonistic behaviour typically consists of squabbles between individuals climbing over or passing each other. This occasionally involves biting. Males who are strangers may wrestle, chase and bite each other. In extreme situations, a male may try to displace a smaller rival from a tree. This involves the larger aggressor climbing up and attempting to corner the victim, who tries either to rush past him and climb down or to move to the end of a branch. The aggressor attacks by grasping the target by the shoulders and repeatedly biting him. Once the weaker individual is driven away, the victor bellows and marks the tree. Pregnant and lactating females are particularly aggressive and will attack individuals that come too close.
Reproduction and development
Koalas are seasonal breeders, and births take place from October to May. Females in oestrus tend to hold their head further back than usual and commonly display tremors and spasms. However, males do not appear to recognise these signs, and have been observed to mount non-oestrous females. Because of his much larger size, a male can usually force himself on a female, mounting her from behind, and in extreme cases the male may pull the female out of the tree. A female may scream and vigorously fight off her suitors, but will submit to one who is dominant, or who is more familiar. The bellows and screams that accompany matings can attract other males to the scene, obliging the incumbent to delay mating and fight the intruders off. These fights may allow the female to assess who is dominant.
The koala has a gestation period lasting 30–35 days, and gives birth to a single young (although twins occur on occasion). As with all marsupials, the young or joey is born while at the embryonic stage, weighing only 0.5 g (0.02 oz). However, it has relatively well-developed lips, forelimbs and shoulders, as well as functioning respiratory, digestive and urinary systems. The joey crawls into its mother's pouch to continue the rest of its development. A female koala has two teats; the joey attaches itself to one of them and suckles for the rest of its pouch life. This species has one of the lowest milk energy production rates in relation to body size of any mammal. The female makes up for this by lactating for as long as 12 months. At seven weeks of age, the head grows longer and becomes proportionally large, pigmentation begins to develop, and the joey's sex can be determined (the scrotum appears in males and the pouch begins to develop in females). At 13 weeks, the joey weighs around 50 g (1.8 oz) and its head has doubled in size. The eyes begin to open and fine fur grows on the forehead, nape, shoulders and arms. At 26 weeks, the fully furred animal resembles an adult, and begins to poke its head out of the pouch.
As the young koala approaches six months, the mother begins to prepare it for its eucalyptus diet by pre-digesting the leaves, producing a faecal pap that the joey eats from her cloacum. The pap is quite different in composition than regular faeces, resembling instead the contents of the caecum, which has a high concentration of bacteria. Eaten for about a month, the pap provides a supplementary source of protein at a transition time from a milk to a leaf diet. The joey fully emerges from the pouch for the first time at six or seven months of age, when it weighs 300–500 g (11–18 oz). It explores its new surroundings cautiously, clinging to its mother for support. By nine months, it weighs over 1 kg (2.2 lb) and develops its adult fur colour. Having permanently left the pouch, it rides on its mother's back for transportation, learning to climb by grasping branches. Gradually, it spends more time away from its mother and at 12 months it is fully weaned, weighing around 2.5 kg (5.5 lb). When the mother becomes pregnant again, her bond with her previous offspring is permanently severed. Newly weaned young are encouraged to disperse by their mother's aggressive behaviour towards them. Females become sexually mature at about three years of age and can then become pregnant; in comparison, males reach sexual maturity when they are about four years old. Males begin to produce sperm, but they have limited reproductive success until they are large enough to stand against a mature rival. Although the chest glands can be functional as early as 18 months of age, males do not begin scent-marking behaviours until they reach sexual maturity. Because the offspring have a long dependent period, female koalas usually breed in alternate years. Favourable environmental factors, such as a plentiful supply of high-quality food trees, allow them to reproduce every year.
Health and mortality
Koalas may live from 13 to 18 years in the wild. While female koalas usually live this long, males may die sooner because of their more hazardous life. Koalas usually survive falls from trees and immediately climb back up, but injuries and deaths from falls do occur, particularly in the case of inexperienced young and fighting males. At around six years of age, the koala's chewing teeth begin to wear down and their chewing efficiency decreases. Eventually, the cusps will disappear completely and the animal will die of starvation or nutritional failure. Koalas have few predators; dingos and large pythons may prey on them, while birds of prey (such as Powerful Owls and Wedge-tailed Eagles) are threats to young. They are generally not subject to external parasites, other than ticks in coastal areas. Koalas may also suffer mange from the mite Sarcoptes scabiei, and skin ulcers from the bacterium Mycobacterium ulcerans, but neither are common. Internal parasites are few and largely harmless. These include the tapeworm Bertiella obesa, commonly found in the intestine, and the nematodes Marsupostrongylus longilarvatus and Durikainema phascolarcti, which are uncommonly found in the lungs. In a three-year study of almost 600 koalas admitted to the Australian Zoo Wildlife Hospital in Queensland, 73.8% of the animals were infected with at least one species of the parasitic protozoal genus Trypanosoma, the most common of which was T. irwini.
Koalas can be subject to pathogens like the Chlamydiaceae, which can cause keratoconjunctivitis, cystitis and reproductive tract infection. Such infections are widespread on the mainland but absent in some island populations. The koala retrovirus (KoRV) may cause Koala Immune Deficiency Syndrome (KIDS), which is similar to AIDS in humans. Prevalence of KoRV in koala populations suggests a trend spreading from the north to the south of Australia. Northern populations are completely infected, while some southern populations (including Kangaroo Island) are free. The animals are vulnerable to bushfires due to their slow movements and the flammability of eucalypt trees. Dehydration and overheating can also prove fatal.
The koala is vulnerable to the effects of climate change. Models of climate change in Australia predict warmer and drier climates, suggesting that the koala's range will shrink in the east and south to more mesic habitats. Droughts also affect the koala's well-being. For example, a severe drought in 1980 caused many Eucalyptus trees to lose their leaves. Subsequently, 63% of the population in southwestern Queensland died, especially young animals that were excluded from prime feeding sites by older, dominant koalas, and recovery of the population was slow. Later, this population declined from an estimated mean population of 59,000 in 1995 to 11,600 in 2009. This 80% reduction is attributed largely to hotter and drier conditions resulting from droughts in most years between 2002 and 2007.
The koala is well known worldwide; it is considered a major draw for Australian zoos and wildlife parks and has been featured in advertisements, games, cartoons and as soft toys. According to biologist Stephen Jackson: "If you were to take a straw poll of the animal most closely associated with Australia, it's a fair bet that the koala would come out marginally in front of the kangaroo". Factors that contribute to the koala's enduring popularity include its childlike body proportions and teddy bear-like face. Such affection for the species is reflected in a stand-up routine by comedian Mitch Hedberg, who stated, "My apartment is infested with koala bears. It's the cutest infestation ever. Way better than cockroaches".
The koala is featured in the Dreamtime stories and mythology of indigenous Australians. The Tharawal people believed that the animal helped row the boat that brought them to the continent. Another myth tells of how a tribe killed a koala and used its long intestines to create a bridge for people from other parts of the world. This narrative highlights the koala's status as a game animal and the length of its intestines. Several stories tell of how the koala lost its tail. In one, a kangaroo cuts it off to punish the koala for being lazy and greedy. Tribes in both Queensland and Victoria regarded the koala as a wise animal and sought its advice. Bidjara-speaking people credited the koala for turning barren lands into lush forests. The animal is also depicted in rock carvings, though not as much as some other species.
The first written reference of the koala was recorded by John Price, servant of John Hunter, the Governor of New South Wales. Price encountered the "cullawine" on 26 January 1798, during an expedition to the Blue Mountains. Early European settlers in Australia considered the koala to be a prowling sloth-like animal with a "fierce and menacing look". At the beginning of the 20th century, the koala's reputation took a more positive turn. It is featured in Ethel Pedley's 1899 book Dot and the Kangaroo, in which it is portrayed as the "funny native bear". Artist Norman Lindsay depicted a more anthropomorphic koala in The Bulletin cartoons, starting in 1904. This character also appeared as Bunyip Bluegum in Lindsay's 1918 book The Magic Pudding. Perhaps the most famous fictional koala is Blinky Bill. Created by Dorothy Wall in 1933, the character appeared in several books and has been the subject of films, TV series, merchandise and a 1986 environmental song by John Williamson. Prince Henry, Duke of Gloucester visited the Koala Park Sanctuary in Sydney in 1934 and was "intensely interested in the bears". His photograph, with Noel Burnet, the founder of the park, and a koala, appeared in the 8 December edition of the Sydney Morning Herald. After World War II, when tourism to Australia increased and the animals were exported to zoos overseas, the koala's international popularity rose. Several political leaders and members of royal families had their pictures taken with koalas, including Queen Elizabeth II, Prince Harry, Crown Prince Naruhito, Crown Princess Masako, Pope John Paul II, US President Bill Clinton, Soviet premier Mikhail Gorbachev and South African President Nelson Mandela.
The song "Ode to a Koala Bear" appears on the B-side to the 1983 Paul McCartney/Michael Jackson duet album Say Say Say. A koala is the main character in Hanna-Barbera's The Kwicky Koala Show and Nippon Animation's Noozles, both of which were animated cartoons of the early 1980s. Food products shaped like the koala include the Caramello Koala chocolate bar and the bite-sized cookie snack Koala's March. Dadswells Bridge in Victoria features a tourist complex shaped like a giant koala, and the Queensland Reds rugby team has a koala as its mascot. The Platinum Koala coin features the animal on the reverse and Elizabeth II on the obverse.
In 2008, the International Union for Conservation of Nature listed the koala under Least Concern for the following reasons: "its wide distribution, presumed large population, and because it is unlikely to be declining at nearly the rate required to qualify for listing in a threatened category". Australian policy makers declined a 2009 proposal to include the koala in the Environment Protection and Biodiversity Conservation Act 1999. In 2012, the Australian Government listed koala populations in Queensland and New South Wales as Vulnerable, because of a 40% population decline in the former and a 33% decline in the latter. Populations in Victoria and South Australia appear to be abundant; however, the Australian Koala Foundation argues that the exclusion of Victorian populations from protective measures is based on a misconception that the total koala population is 200,000, whereas they believe it is probably less than 100,000.
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. 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 these cullings was probably the first wide-scale environmental issue that rallied Australians. Despite the growing movement to protect native species, the poverty brought about by the drought of 1926–28 led to the killing of another 600,000 koalas during a one-month open season in August 1927.
One of the biggest anthropogenic threats to the koala is habitat destruction and fragmentation. In coastal areas, the main cause of this is urbanisation, while in rural areas habitat is cleared for agriculture. Native forest trees are also taken down to be made into wood products. Since European arrival, localised deforestation of eucalypts in Australia ranges from 33 to 93%. In addition, Acacia habitats, which can also support koala populations, declined by 80% overall. In 2000, Australia ranked fifth in the world by deforestation rates, having cleared 564,800 hectares (1,396,000 acres). The geographical range of the koala has shrunk by more than 50% since European arrival, largely due to fragmentation of habitat in Queensland. The koala's "vulnerable" status in Queensland and New South Wales means that developers in these states must consider the impacts on this species when making building applications. In addition, koalas live in many protected areas.
While urbanisation can pose a threat to koala populations, the animals can survive in urban areas provided there are enough trees, though urban koalas are vulnerable to collisions with vehicles and attacks by domestic dogs. Injured koalas are often taken to wildlife hospitals and rehabilitation centres. In a 30-year retrospective study performed at a New South Wales koala rehabilitation centre, it was found that trauma (usually resulting from a motor vehicle accident or dog attack) was the most frequent cause of admission, followed by symptoms of the bacterial disease chlamydiosis. Wildlife caretakers are issued with special permits but have to release the animals back into the wild when they are either well enough or, in the case of joeys, old enough. As with most native animals, the koala cannot legally be kept as a pet in Australia or anywhere else.
Since 1870, koalas have been introduced to several coastal and offshore islands, including Kangaroo Island and French Island. Their numbers have grown to the thousands, and since the islands are not large enough to sustain such high koala numbers, overbrowsing has become a problem. Since the 1990s, government agencies have tried to control their numbers by culling, but public and international outcry has forced the use of translocation and sterilisation instead.
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