Koala

The koala (Phascolarctos cinereus), sometimes wrongly called the koala bear, is a tree-dwelling plant-eating marsupial from Australia. It is the only living member of its family, Phascolarctidae. Its closest living relatives are the wombats. Koalas live in coastal areas in the east and south of the continent, including Queensland, New South Wales, Victoria, and South Australia. (For other uses, see Koala (disambiguation).)

Koalas are easy to recognise. They have a stout body with no tail, a large head, round fluffy ears, and a big dark nose. An adult koala is about 60 to 85 centimetres long and weighs 4 to 15 kilograms. Their fur ranges from silver grey to chocolate brown. Koalas from the northern areas are usually smaller and lighter in colour than those further south. These groups may be separate subspecies, but not all scientists agree.

Koalas usually live in open Eucalyptus woodland, because eucalyptus leaves make up most of their food. This diet has little nutrition and contains toxic compounds that keep most other animals away. Koalas move very little and sleep up to twenty hours a day. They live alone, and only mothers bond with their young. Adult males bellow to scare away rivals and attract mates, and they mark their presence with smells from scent glands on their chests. Like other marsupials, koalas are born at a very early stage. The tiny babies, called joeys, crawl into their mothers' pouches, where they live for their first six to seven months. They are fully weaned at around one year old.

Koalas have few natural enemies, but they can get sick from pathogens such as Chlamydiaceae bacteria and the koala retrovirus. The International Union for Conservation of Nature lists koalas as a vulnerable species. Their survival is threatened by habitat destruction from farming and growing cities, as well as by droughts and wildfires, some of which are linked to climate change. In February 2022, the koala was officially listed as endangered in the Australian Capital Territory, New South Wales, and Queensland. In parts of South Australia and Victoria, however, there are far too many koalas, and their numbers are growing at unsustainable levels.

Because of their distinctive appearance, koalas, along with kangaroos, are recognised around the world as symbols of Australia. Aboriginal Australians hunted koalas and showed them in myths and cave art for thousands of years. The first recorded meeting between a European and a koala took place in 1798. In 1810, naturalist George Perry published an image of the animal. Botanist Robert Brown wrote the first detailed scientific description in 1814, although his work remained unpublished for 180 years. Artist John Gould illustrated and described the koala, which introduced the species to the British public. Later, in the 19th century, English scientists discovered more details about the animal's biology.

Etymology

The word "koala" comes from the Dharug word gula, which means 'no water'. The "u" sound was first written as "oo" in English spelling, in forms like coola or koolah, which had two syllables. Later, the spelling became "oa", and the word is now said in three syllables (ko-a-la), possibly by mistake based on that new spelling. Another idea is that "koala" was an Aboriginal name from the Hawkesbury River area near Sydney.

White settlers adopted the word, and it became one of hundreds of Aboriginal loan words in Australian English. The animal was also often called the "native bear", and later the "koala bear", because it looks a bit like a bear. "Koala" is one of several Aboriginal words that entered International English, along with words like "didgeridoo" and "kangaroo". The animal's generic name, Phascolarctos, comes from Greek words meaning 'pouch' and 'bear'. Its specific name, cinereus, is Latin for 'ash coloured'.

Taxonomy

The name Phascolarctos was given in 1816 by French zoologist Henri Marie Ducrotay de Blainville, who did not give it a specific name until later. In 1819, German zoologist Georg August Goldfuss gave it the binomial Lipurus cinereus. Because Phascolarctos was published first, under the International Code of Zoological Nomenclature, it has priority as the official genus name. Other names were suggested later by European writers, including Anselme Gaëtan Desmarest, René-Primevère Lesson and John Edward Gray. The koala is classified with wombats (family Vombatidae) and several extinct families, such as marsupial tapirs, marsupial lions and giant wombats. These belong to the suborder Vombatiformes within the order Diprotodontia. 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 kinds of koalas. During the Oligocene and Miocene, koalas lived in rainforests and ate a wider range of foods. As the Australian continent dried out, rainforests declined and open Eucalyptus woodlands spread. The genus Phascolarctos split from Litokoala in the late Miocene and developed features that helped it live on a eucalyptus diet. P. cinereus may have grown smaller from a giant koala (P. stirtoni) after many giant animals disappeared in the late Pleistocene, although a 2008 study questioned this idea. The fossil record of the modern koala goes back at least to the middle Pleistocene.

Three subspecies have been described: the Queensland koala, the New South Wales koala and the Victorian koala. They differ in pelage colour and thickness, body size and skull shape. The Queensland koala is the smallest, and the Victorian koala is the largest. The borders between these groups follow state borders, and scientists disagree about whether they are truly separate subspecies. Koala populations are also highly inbred, with low genetic variation. 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 sturdy animal with a large head and a tail that is small or missing. It is 60 to 90 cm (24 to 35 in) long and weighs 4 to 15 kg (8.8 to 33.1 lb), which makes it one of the largest tree-living marsupials. Males are about 50% larger than females and have more curved noses and chest glands that show up as bald patches. A strong ring of muscle keeps the female's pouch closed around her young. The koala's thick fur is densest on its back and ranges from light grey to chocolate brown. Its curved, sharp claws and grip on branches help it climb trees.

For a mammal, the koala has a disproportionately small brain and a fairly smooth surface. Its brain is about 60% smaller than that of a typical diprotodont. Large amounts of cerebrospinal fluid lighten the brain, which may protect it if the koala falls from a tree. The koala has a good sense of smell and round ears that help it hear well. Its voice can make deeper sounds than would otherwise be possible for its size, thanks to vocal cords in the soft palate.

The koala's diet is low in nutrients, toxic, and tough, so it has special features to cope with it. It bites leaves with its front teeth and clips them with its cheek teeth at the petiole. Koalas may store food in their cheek pouches before chewing it. Koalas are hindgut fermenters with a very long caecum, where food can stay for a long time. They can break down poisonous plant secondary metabolites, phenolic compounds and terpenes, because they make cytochrome P450, which neutralises these poisons in the liver.

Distribution and habitat

Koalas live across roughly 1,000,000 km² (390,000 sq mi) and in 30 ecoregions. They can be found in both warm and cool areas, in places ranging from dense woodlands to more spread-out forests. In dry areas with semi-arid climates, they prefer riparian habitats, where nearby streams and creeks offer shelter during droughts and extreme heat. Koalas live across mainland eastern and southeastern Australia, including the states of Queensland, New South Wales, Victoria, and South Australia. They were also introduced to several nearby islands. The population on Magnetic Island marks the northern edge of their range.

Fossil evidence shows that koalas once lived 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. Koalas were introduced to Western Australia at Yanchep in 1938, but that population was reduced to 4 individuals by 2022.

Behaviour and ecology

Koalas mostly eat eucalypt leaves, but they also eat leaves from trees such as Acacia, Allocasuarina, Callitris, Leptospermum, and Melaleuca. They prefer leaves with more protein than fibre and lignin. Their favourite eucalypts are Eucalyptus microcorys, E. tereticornis, and E. camaldulensis. Koalas get most of their water from leaves. They are mostly active at night and sleep about 20 hours a day. They spend little time on the ground and groom themselves with their hind paws. Koalas are not very social and spend about 15 minutes a day on social behaviours. Adult males call with loud bellows that can travel far through the forest. They also make snarls, wails, and screams, and they communicate with facial expressions.

A bellowing male in the Lone Pine Koala Sanctuary

Koalas breed in a season and give birth from October to May. Females in oestrus shake their bodies and lean their heads back, and males may try to mate with them. A female usually gives birth to one joey, and sometimes to twins. The newborn crawls into its mother's pouch to keep developing. At six or seven months, it leaves the pouch for the first time. Females become sexually mature at about three years old, and males at about four. Koalas live from 13 to 18 years in the wild. They have few predators, including dingos, large pythons, and some birds of prey. Koalas can get infections such as keratoconjunctivitis, and koala retrovirus (KoRV) may cause koala immune deficiency syndrome (KIDS), which is similar to AIDS in humans. Bushfires are a danger because koalas move slowly and eucalypt trees burn easily. Dehydration and overheating can also be fatal, and climate change is a threat to koalas.

Relation to humans

The first written record of the koala came from John Price, a servant of John Hunter, the Governor of New South Wales. Price saw the "cullawine" on 26 January 1798 during a trip to the Blue Mountains, but his notes were not published until nearly a century later, in Historical Records of Australia. In 1802, French-born explorer Francis Louis Barrallier saw the animal when his two Aboriginal guides brought back koala feet they meant to eat. He kept them and sent them with his notes to Philip Gidley King, who passed them to Joseph Banks. Reports of the "Koolah" appeared in the Sydney Gazette in late 1803, and King asked artist John Lewin to paint the animal. One of Lewin's three pictures was printed in Georges Cuvier's Le Règne Animal (The Animal Kingdom) (1827). Robert Brown wrote the first formal scientific description in 1803, based on a female captured near what is now Mount Kembla in the Illawarra region of New South Wales, and Ferdinand Bauer drew its skull, throat, feet, and paws. Brown's work stayed unpublished and largely unnoticed. William Paterson, who had befriended Brown and Bauer, wrote an eyewitness report that became the basis for Everard Home's writings. Home published his report in 1808 and gave the koala the scientific name Didelphis coola. George Perry published the first official image of the koala in 1810, calling it the "New Holland Sloth" and showing his dislike of the animal.

John Gould illustrated and described the koala in his three-volume work The Mammals of Australia (1845–1863), which introduced it to the public. Richard Owen gave an early description of its internal body to the Zoological Society of London and noted its similarity to the wombat. George Robert Waterhouse was the first to correctly classify the koala as a marsupial, and he compared it to the fossil species Diprotodon and Nototherium. Gerard Krefft, of the Australian Museum in Sydney, compared it to fossil marsupials in 1871. Britain received its first living koala in 1881, obtained by the Zoological Society of London. William Alexander Forbes later studied the animal and wrote about parts of its body that had not been described before. Scottish embryologist William Caldwell, known for his work on the platypus, described the koala's development in 1884 and used this to map out its evolutionary history alongside the monotremes.

The koala is known around the world and draws many visitors to Australian zoos and wildlife parks. It benefited Australian tourism by over $1 billion in 1998 and has grown since. Koala souvenir soft toys are popular with tourists, and the koala appears in many stories, from the Dreamtime tales and mythology of Indigenous Australians, where the Tharawal people believed it helped them reach Australia, to books and cartoons. Early European settlers saw it as a creeping sloth-like animal, but its reputation improved around 1900 when Ethel Pedley wrote it into Dot and the Kangaroo as the "funny native bear." Artist Norman Lindsay drew a more anthropomorphic koala in The Bulletin cartoons, and it later appeared in his book The Magic Pudding. The most famous fictional koala is Blinky Bill, created by Dorothy Wall in 1933. The koala also appeared on an Australian stamp in 1930, and it has been featured in songs, cartoons, foods such as the Caramello Koala chocolate bar, and a rugby team's logo, the Queensland Reds.

Political leaders and members of royal families have had their pictures taken with koalas, including Queen Elizabeth II, Prince Harry, Crown Prince Naruhito, Crown Princess Masako, Pope John Paul II, Bill Clinton, Mikhail Gorbachev and Nelson Mandela. At the 2014 G20 Brisbane summit, hosted by Prime Minister Tony Abbott, many world leaders, including Vladimir Putin and Barack Obama, were photographed holding koalas. This 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, as a form of "soft power diplomacy" similar to the "panda diplomacy" practised by China.

Conservation

The koala was first listed as Least Concern on the Red List, but it was reassessed as Vulnerable in 2014. In February 2022, it was listed as endangered in the Australian Capital Territory, New South Wales and Queensland. Australian policymakers declined a 2009 proposal to include the koala in the Environment Protection and Biodiversity Conservation Act 1999. In 2021, the koala population was estimated at 92,000, down from 185,000 two decades earlier. In 2025, the CSIRO's National Koala Monitoring Program gave a higher estimate of 729,000–918,000 koalas, using improved counting methods. At the start of the 20th century, there were 8 to 10 million koalas.

Koalas were heavily hunted by European settlers in the early 20th century, mostly for their fur. Between 1888 and 1927, roughly 8 million koalas were hunted. The first successful conservation efforts began with Lone Pine Koala Sanctuary in Brisbane and Koala Park Sanctuary in Sydney. Today, one of the biggest human-caused threats is the loss and splitting up of habitat, mainly from towns spreading and land being cleared for farms. Cars and dogs kill about 4,000 koalas each year. In some places, koala numbers are now too high. As of early 2026, koalas in parts of South Australia and Victoria are over-abundant, including in the Mount Lofty Ranges near Adelaide.