Koala

The word "koala" comes from the Dharug , meaning . Although the vowel "u" was originally written in the English orthography as "oo" (in spellings such as coola or koolah—two syllables), the spelling for that sound later became "oa"; the word is now pronounced in three syllables (ko-a-la) possibly in error based on that new spelling. Another hypothesis is that "koala" was an aboriginal name from the Hawkesbury River district near Sydney. Adopted by white settlers, the word "koala" became one of hundreds of Aboriginal loan words in Australian English, where it was also commonly referred to as "native bear", later "koala bear", for its resemblance to a bear. The koala's generic name, Phascolarctos, is derived from the Greek words () and () . The specific name, , is Latin for . ==Taxonomy==

The generic name Phascolarctos was given in 1816 by French zoologist Henri Marie Ducrotay de Blainville, who did not give it a specific name until further review. In 1819, 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 genus name. French naturalist Anselme Gaëtan Desmarest coined the name Phascolarctos fuscus in 1820, suggesting that the brown-coloured versions were a different species than the grey ones. Other names suggested by European authors included Marodactylus cinereus by Goldfuss in 1820, P. flindersii by René Primevère Lesson in 1827, and P. koala by John Edward Gray in 1827. Evolution 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. The Vombatiformes are a sister group to a clade that includes macropods (kangaroos and wallabies) and possums. The koala's lineage possibly branched off around 40 million years ago during the Eocene. The modern koala is the only extant member of Phascolarctidae, a family that includes several extinct genera and species. During the Oligocene and Miocene, koalas lived in rainforests and had broader diets. Some species, such as 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. Like the modern species, prehistoric koalas had well developed ear structures, which suggests that they also made long-distance vocalisations and had a relatively inactive lifestyle. and had several adaptations that allowed it to live on a eucalyptus diet: the palate shifted towards the front of the skull; the upper teeth were lined by thicker bone, molars became relatively low compared to the jaw joint and with more chewing surface; the pterygoid fossa shrank; The fossil record of the modern koala extends back at least to the middle Pleistocene. }} }} Genetics and variations Three subspecies have been described: the Queensland koala (Phascolarctos cinereus adustus, Thomas 1923), the New South Wales koala (Phascolarctos cinereus cinereus, Goldfuss 1817), and the Victorian koala (Phascolarctos cinereus victor, Troughton 1935). These forms are distinguished by pelage colour and thickness, body size, and skull shape. The Queensland koala is the smallest, with silver or grey short hairs and a shorter skull. The Victorian koala is the largest, with shaggier, brown fur and a wider skull. The geographic limits of these variations are based on state borders, and their status as subspecies is disputed. A 1999 genetic study suggests koalas exist as a cline within a single evolutionarily significant unit with limited gene flow between local populations. Other studies have found that koala populations are highly inbred with low genetic variation. Such low genetic diversity may have been caused by population declines during the late Pleistocene. Rivers and roads limit gene flow and contribute to the isolation of southeast Queensland populations. In April 2013, scientists from the Australian Museum and Queensland University of Technology announced they had fully sequenced the koala genome. ==Characteristics==

The koala is a robust animal with a large head and vestigial or non-existent tail. It has a body length of and a weight of , The pelage of the koala is denser on the back. Back fur colour varies from light grey to chocolate brown. The koala has curved, sharp claws well adapted for climbing trees. The large forepaws have two opposable digits (the first and second, which are opposable to the other three) that allow them to grip small branches. On the hind paws, the second and third digits are fused, a typical condition for members of the Diprotodontia, and the attached claws (which are still separate) function like a comb. The brain's surface is fairly smooth and "primitive". with a good sense of smell, and it is known to sniff the oils of individual branchlets to assess their edibility. , premolars (dark), diastema, canines, incisors The koala has several adaptations for its low nutrient, toxic, and fibrous diet. The partially worn molars of koalas in their prime are optimal for breaking leaves into small particles, resulting in more efficient stomach digestion and nutrient absorption in the small intestine, Koalas are hindgut fermenters, and their digestive retention can last 100 hours in the wild or 200 hours in captivity. The koala replaces lost water at a lower rate than species such as some possums. It maintains water by absorbing it in the caecum, resulting in drier faecal pellets packed with undigested fibre. ==Distribution and habitat==

The koala's range covers roughly , and 30 ecoregions. It ranges throughout mainland eastern and southeastern Australia, including the states of Queensland, New South Wales, Victoria, and South Australia. The koala was introduced to several nearby islands. Fossil evidence shows that the koala's range stretched as far west as southwestern Western Australia during the late Pleistocene. They were likely driven to extinction in these areas by environmental changes and hunting by Aboriginal peoples. ==Behaviour and ecology==

Foraging and activities Koalas are herbivorous, and while most of their diet consists of eucalypt leaves, they can be found in trees of other genera, such as Acacia, Allocasuarina, Callitris, Leptospermum, and Melaleuca. They prefer plant matter with higher protein than fibre and lignin. Despite its reputation as a picky eater, the koala is more generalist than some other marsupial species, such as the greater glider. The koala does not need to drink often as it can get enough water from the leaves, They are predominantly active at night and spend most of their waking hours foraging. They typically eat and sleep in the same tree, possibly for as long as a day. It curls up when it gets cold and wet. The koala usually grooms itself with its hind paws, with their double claws, but it sometimes uses its forepaws or mouth. The territories of dominant males are found near breeding females, while younger males must wait until they reach full size to challenge for breeding rights. Chest gland secretions are complex chemical mixtures—about 40 compounds were identified in one analysis—that vary in composition and concentration across season and age. Adult males communicate with loud bellows—"a long series of deep, snoring inhalations and belching exhalations". Because of their low frequency, these bellows can travel far through the forest. They also bellow to advertise their presence when they change trees. females pay more attention to bellows by 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. In extreme situations, a larger male may try to displace a smaller rival from a tree, chasing, cornering, and biting it. Once the individual is driven away, the victor bellows and marks the tree. The gestation period lasts 33–35 days, and a female gives birth to one joey or occasionally, twins. The young are born tiny and barely formed, weighing no more than . However, their lips, forelimbs, and shoulders are relatively advanced, and they can breathe, defecate, and urinate. The joey crawls into its mother's pouch to continue its development. A nine month old joey has its adult coat colour and weighs . Having permanently left the pouch, it rides on its mother's back for transportation, learning to climb by grasping branches. although they can experience spermatogenesis as early as two years. Koalas have few predators. Dingos, large pythons and some birds of prey may take them.. In a three-year study of almost 600 koalas taken to the Australia Zoo Wildlife Hospital in Queensland, 73.8% of the animals were infected with parasitic protozoal genus Trypanosoma, the most frequent of which was T. irwini. Koalas can be subject to pathogens such as Chlamydiaceae bacteria, 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 it spread from north to south, for only southern populations have virus-free individuals. In 2026, genomic analysis of multi-generation captive koala populations identified inherited KoRV integrations associated with cancer risk and reproductive outcomes. The findings may inform captive breeding programs. The animals are vulnerable to bushfires due to their slow speed and the flammability of eucalypt trees. ==Relation to humans==

History The first written reference to 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, but his remarks would first be published in Historical Records of Australia, nearly a century later. coined the scientific name Didelphis coola. Naturalist and popular artist John Gould illustrated and described the koala in his three-volume work The Mammals of Australia (1845–1863) and introduced the species, as well as other members of Australia's little-known faunal community, to the public. In this widely cited publication, he provided an early description of its internal anatomy, and noted its general structural similarity to the wombat. and used this new information to convincingly map out the evolutionary timeline of the koala and the monotremes. The event gave rise to the term "koala diplomacy", which became the Oxford Word of the Month for December 2016. The term also includes the loan of koalas by the Australian government to overseas zoos in countries such as Singapore and Japan, as a form of "soft power diplomacy", like the "panda diplomacy" practised by China. ==Conservation==

The koala was originally classified as Least Concern on the Red List, and reassessed as Vulnerable in 2014. The described population was determined in 2012 to be "a species for the purposes of the EPBC Act 1999" in Federal legislation. Australian policymakers declined a 2009 proposal to include the koala in the Environment Protection and Biodiversity Conservation Act 1999. The Australian Government's Threatened Species Scientific Committee estimated that the 2021 koala population was 92,000, down from 185,000 two decades prior. The Australian Koala Foundation estimated in 2022 that there could be 43,000–100,000 koalas. This compares with 8 to 10 million at the start of the 20th century. The koala was heavily hunted by European settlers in the early 20th century, Urban populations have distinct vulnerabilities: collisions with vehicles and attacks by domestic dogs. Cars and dogs kill about 4,000 animals every year; together they account for two thirds of all koala deaths. such as the use of fencing to channel animals toward an underpass, in some cases adding a walkway to an existing culvert. Injured koalas are often taken to wildlife hospitals and rehabilitation centres. However, as of early 2026, the koala population in parts of South Australia and Victoria are over-abundant. In Victoria, they are over-grazing in Cape Otway and French Island. Numbers have been growing rapidly in the Mount Lofty Ranges, near Adelaide in South Australia, which represents around 10 per cent of the national population, and expected to expand by around 17 to 25 per cent over the next 25 years. A study published in January 2026 warns that to the point where they could experience starvation, and suggests various methods of population control. Numbers were abundant on Kangaroo Island (KI) at around 48,000, before the 2020 Kangaroo Island bushfires, and in 2026 estimated to number around 5-10,000. On this island, these koalas are not affected by chlamydophila pneumoniae, due to the isolation from other colonies. Koalas are not native to South Australia, having been exported to the Mount Lofty Ranges and KI from French Island in Victoria around 1920. ==See also==