Koala

The koala (Phascolarctos cinereus), sometimes wrongly called the koala bear, is a plant-eating marsupial that lives in trees. It comes 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 country, 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, 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 can be silver grey or chocolate brown. Koalas from the north 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 food 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 make loud calls to scare away rivals and attract mates. They also 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 the loss of their homes to farms and growing cities. Droughts and wildfires also cause problems, and some of these 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 too fast to be sustainable.

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, but his work was not published for 180 years. Artist John Gould drew and described the koala, which introduced the species to the British public. Later, in the 19th century, English scientists learned more about how the animal lives and works inside its body.

Etymology

The word "koala" comes from the Dharug word gula, which means 'no water'. In early English spelling, the "u" sound was written as "oo", in forms like coola or koolah, which had two syllables. Later, the spelling changed to "oa". Because of this new spelling, the word is now often 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. It became one of many 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. He 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 grouped 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 family line may have split 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 shrank 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 small tail, or sometimes no tail at all. It is 60 to 90 cm (24 to 35 in) long and weighs 4 to 15 kg (8.8 to 33.1 lb). This makes it one of the largest animals that lives in trees and carries its young in a pouch. Males are about 50% larger than females. They have more curved noses and chest glands that make bald patches. A strong ring of muscle keeps the female's pouch closed around her young. The koala's thick fur is thickest on its back. Its color ranges from light grey to chocolate brown. Its curved, sharp claws and strong grip help it climb trees.

For an animal of its kind, the koala has a disproportionately small brain and a fairly smooth surface. Its brain is about 60% smaller than that of a typical diprotodont. A lot of cerebrospinal fluid makes the brain lighter, which may help 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. It can make deeper sounds than you might expect for its size, because of its vocal cords in the soft palate.

The koala's food is low in nutrients, can be poisonous, and is tough to eat, so the koala has special ways to deal 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 about 1,000,000 km² (390,000 sq mi) and in 30 ecoregions. They can be found in both warm and cool areas, in places from thick woodlands to more open 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 on the mainland of eastern and southeastern Australia, including the states of Queensland, New South Wales, Victoria, and South Australia. They were also brought 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 long ago. They were likely driven out of these areas by changes in the environment and by hunting by Aboriginal peoples. Koalas were brought to Western Australia at Yanchep in 1938, but by 2022 that population had shrunk to just 4 animals.

Behaviour and ecology

Koalas mostly eat eucalypt leaves. They also eat leaves from trees such as Acacia, Allocasuarina, Callitris, Leptospermum, and Melaleuca. They like leaves that have more protein and less fibre and lignin. Their favourite eucalypts are Eucalyptus microcorys, E. tereticornis, and E. camaldulensis. Koalas get most of their water from the leaves they eat. They are mostly active at night and sleep about 20 hours a day. They spend little time on the ground. They clean their fur with their back feet. Koalas are not very social and spend about 15 minutes a day on social behaviour. Adult males make loud bellows that can be heard far away in the forest. They also make snarls, wails, and screams, and they show how they feel with their faces.

A bellowing male in the Lone Pine Koala Sanctuary

Koalas breed during one season each year and give birth from October to May. Females that are ready to mate shake their bodies and lean their heads back. 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 growing. At six or seven months, it leaves the pouch for the first time. Females are ready to have young at about three years old, and males at about four. In the wild, koalas live from 13 to 18 years. They have few predators, including dingos, large pythons, and some birds of prey. Koalas can get infections such as keratoconjunctivitis. Koala retrovirus (KoRV) may cause koala immune deficiency syndrome (KIDS), which is similar to AIDS in humans. Bushfires are dangerous because koalas move slowly and eucalypt trees burn easily. Dehydration and overheating can also be deadly, 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. His notes were not published until almost a century later, in Historical Records of Australia. In 1802, French-born explorer Francis Louis Barrallier saw the animal too. His two Aboriginal guides had brought back koala feet. 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. 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) in 1827. Robert Brown wrote the first formal scientific description in 1803. He based it on a female caught near what is now Mount Kembla in the Illawarra region of New South Wales. Ferdinand Bauer drew its skull, throat, feet, and paws. Brown's work stayed unpublished and was mostly unnoticed. William Paterson, who had become friends with Brown and Bauer, wrote an eyewitness report. It became the basis for Everard Home's writings. Home published the report in 1808 and gave the koala the scientific name Didelphis coola. In 1810, George Perry published the first official picture of the koala. He called it the "New Holland Sloth," and he did not seem to like the animal.

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

The koala is known around the world. It draws many visitors to Australian zoos and wildlife parks. It helped Australian tourism by over $1 billion in 1998, and its popularity has grown since then. Koala soft toys are popular with tourists. The koala appears in many stories. In the Dreamtime tales and mythology of Indigenous Australians, the Tharawal people believed it helped them reach Australia. It also appears in books and cartoons. Early European settlers saw it as a creeping sloth-like animal. 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. It later appeared in his book The Magic Pudding. The most famous fictional koala is Blinky Bill, created by Dorothy Wall in 1933. A koala appeared on an Australian stamp in 1930. It has also been featured in songs and cartoons. It appears on foods such as the Caramello Koala chocolate bar, and it is the logo of a rugby team, the Queensland Reds.

Political leaders and members of royal families have had their photos taken with koalas. These include 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 were photographed holding koalas. These included Vladimir Putin and Barack Obama. This gave rise to the term "koala diplomacy," which became the Oxford Word of the Month for December 2016. The term also refers to the Australian government lending koalas to overseas zoos. This is a kind 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 in 2014 it was reassessed as Vulnerable. In February 2022, it was listed as endangered in the Australian Capital Territory, New South Wales and Queensland. Australian leaders decided not to add the koala to the Environment Protection and Biodiversity Conservation Act 1999 after a 2009 proposal. In 2021, the koala population was estimated at 92,000, down from 185,000 twenty years earlier. In 2025, the CSIRO's National Koala Monitoring Program gave a higher estimate of 729,000 to 918,000 koalas, because it used better counting methods. At the start of the 20th century, there were millions of koalas.

In the early 20th century, European settlers hunted koalas a lot, mostly for their fur. The koala population became very small because of this. The first successful conservation efforts began with Lone Pine Koala Sanctuary in Brisbane and Koala Park Sanctuary in Sydney. Today, one of the biggest threats to koalas is the loss and breaking up of their habitat. This happens mainly when towns grow and land is cleared for farms. Cars and dogs harm many koalas each year. In some places, there are now too many koalas. As of early 2026, koalas in parts of South Australia and Victoria are more numerous than the land can comfortably support, including in the Mount Lofty Ranges near Adelaide.