Koala (Phascolarctos cinereus)
|Size||Average male head-body length (northern part of range): 70.5 cm (2)|
Average female head-body length (northern part of range): 68.7 cm (2)
Average male head-body length (southern part of range): 78.2 cm (2)
Average female head-body length (southern part of range): 71.6 cm (2)
Average male weight (northern part of range): 6.5 kg (3)
Average female weight (northern part of range): 5.1 kg (3)
Average male weight (southern part of range): 12 kg (2)
Average female weight (southern part of range): 8.5 kg (2)
- Like other marsupials, the female koala has a pouch with a powerful muscle to prevent its young from falling out
- A newborn 'joey' koala is only about 2 centimetres long and it is blind and furless
- Koalas in southern parts of Australia are larger and have thicker fur than those in the north
- Gumleaves provide almost all of the moisture a koala needs, and it rarely drinks water
- Koalas have evolved to cope with eating eucalyptus leaves even though they are fibrous and very toxic
The koala is classified as Least Concern (LC) on the IUCN Red List (1). It is also listed as Vulnerable in the southeast Queensland bioregion under the Nature Conservation Act 1992, and classified as Vulnerable under the New South Wales Threatened Species Conservation Act 1995. In South Australia, koalas are listed as Rare (4).
One of Australia’s most iconic animals, the koala (Phascolarctos cinereus) is bear-like in appearance with a stout body and large paws, but is in fact a marsupial. The fur is predominantly grey to light brown, being lighter and shorter in the warmer north of its range, where the koala is also smaller (3). The chin, chest, insides of the ears and forelimbs are white, with long, white hairs edging the large, round ears. The grey rump is speckled with white (4).
The koala is well adapted to a life spent mainly in the canopy of trees, possessing unusually long forelimbs in relation to their hind limbs, and specially adapted, padded paws to aid in gripping and climbing. It also has large claws, except for on the first digit of the hind paw. The first and second digits of the front paws, as well as the first digits of the hind paws, are opposed like thumbs to help grip branches. The second and third digits of the hind paws are partially fused together to form a grooming claw for removing ticks (4).
The male koala is larger with a broader face than the female. Mature males are further distinguishable from females by a brown gland on the chest that produces scent used to mark trees within their territory. Like other marsupials, the female koala has a pouch with a strong, contracting, ring-shaped muscle around the backwards-facing opening, which prevents the young from falling out (4).
Found only in Australia, the koala occurs in a band down the eastern and southern coasts and inland areas of Queensland, New South Wales, Victoria and South Australia, as well as on islands off Queensland, Victoria and South Australia (4).
The koala lives in eucalypt forests and woodlands, in cool-temperate to tropical areas (3).
The koala is primarily nocturnal, spending most of its time in the branches of trees where it can feed, rest and gain some protection from ground-dwelling predators (5). Much of the koala’s time is spent sleeping, and when awake it is still a fairly sedentary species. It feeds on the leaves of a variety of trees, but the bulk of its diet comes from only a few eucalypt species (5), with marked local and regional differences for the eucalypt species preferred (4). An adult koala consumes about 500 grams of fresh leaves per day (3). Eucalyptus leaves are very fibrous and highly toxic. However, koalas have evolved to cope with these problems with special cheek teeth that grind the leaves into a fine paste, which is then digested by microbes in the caecum part of the intestine. The koala’s caecum is unusually long, at around 200 centimetres, and has a blind end, unlike in most other mammals. Some of the poisons are detoxified in the liver. This diet does not provide much energy, so the koala spends long periods sleeping, which helps compensate for this (3). There is also evidence that koalas may perform myrecism - regurgitating and re-chewing partially digested food, which extracts more energy from the food (6).
Both the male and female koala reaches sexual maturity at around two years old, but the male is rarely large enough to compete for mating access until four years old. Females normally give birth to one young every year, but older females may only reproduce every second year. The newborn ‘joey’ is underdeveloped and crawls rapidly through the mother’s fur to her pouch, where it suckles for six months. In addition to milk, the joey feeds on a substance called ‘pap’, which is a liquefied form of the mother’s faeces and provides the joey’s digestive system with the micro-organisms necessary for digesting eucalyptus leaves (7). After leaving the pouch, the joey rides on its mother’s belly, and later rides on her back. It normally remains with its mother until the following year’s joey has emerged from the pouch (3).
Koala numbers reached a low point in the 1930s, when hunting for the fur trade made many local populations extinct, including that in South Australia. Other factors in their decline included land clearing, disease, fire and drought. Whilst the koala population as a whole has recovered somewhat since then, its current conservation status varies across its range (3).
Major threats to the koala now include land clearing and urbanization, which result in the loss, fragmentation and degradation of habitats. The koala is confined by its diet to a specialised habitat, of which around 80 percent has been destroyed since Europeans settled in Australia. It is also threatened by fires, droughts and disease (particularly due to the Chlamydia bacterium) (4), while around 4,000 koalas are thought to be killed each year by collisions with road traffic and predation by dogs (8). Recently there has been a lot of attention in the media suggesting that koalas in some isolated patches of habitat have been the cause of defoliation of eucalyptus trees, resulting in calls for a cull of the koalas in these areas. That the koalas are to blame is a contentious issue amongst scientists and authorities and there is evidence to suggest that several other factors may be the cause (4).
Global climate change has been identified as a further threat to the koala. Climate change is predicted to result in increased atmospheric carbon dioxide levels, which causes plants to grow faster. This reduces protein levels in plants and increases tannin levels. As carbon dioxide levels continue to rise, the koala will need to cope with increasingly nutrient-poor and tannin-rich eucalypt leaves. The koala may respond to this by travelling further in search of the most nutritious leaves. However, dispersing koalas will be at increased risk of predation and will often find themselves having to cross main roads and coming into contact with domestic animals (8).
Climate change is predicted to cause an increase in drought frequency and fire-causing weather in many parts of Australia, owing to reduced rainfall levels, increased evaporation rates and an overall temperature increase of about 1 degree Celsius by 2030. Koalas are particularly vulnerable to bushfires as their slow movement and tree-dwelling lifestyle makes it difficult for them to escape and their food supply can be destroyed. Their lack of mobility and specialisation upon specific tree species also makes them extremely vulnerable to droughts (8).
Despite being a protected species, the koala population has declined markedly due to habitat loss, and many populations are now living in isolated patches of habitat, putting them at greater risk of localised extinctions. Remaining koala habitat is mostly on privately-owned land, meaning landowners should be given responsibility to conserve this species. As an important step to achieve national legislation that would effectively protect koala habitat in privately-owned land and elsewhere, in July 2004 the Australian Koala Foundation submitted a nomination to the Australian Government, supported by a large amount of scientific data, to list the koala as Vulnerable nationally. To date this has not been achieved. Without legislation that encourages landowners to protect koala habitat on their land, there are fears koala numbers will decline to such an extent that populations will be incapable of ever recovering (4).
Legislation, along with continued research and monitoring, will be necessary to prevent this Australian icon from further declining as a result of competing land use pressures (4).
For further information on this species see:
Australian Koala Foundation:
BBC Wildlife Finder:
Authenticated (04/05/05) by Jo Knights Manager (Education) of the Australian Koala Foundation.
- Marsupial: a diverse group of mammals characterised by their reproduction. The embryo is born 11-35 days after conception. The tiny neonate crawls into the marsupium (pouch) and attaches to a teat where it stays for a variable amount of time. They also differ from placental mammals in their dentition.
- Nocturnal: active at night.
- Territory: an area occupied and defended by an animal, a pair of animals or a colony.
IUCN Red List (April, 2009)
- Strahan, R. (1998) The Mammals of Australia. Reed New Holland/Australian Museum, Sydney.
- Macdonald, D. (2001) The New Encyclopedia of Mammals. Oxford University Press, Oxford.
Australian Koala Foundation (May, 2005)
Animal Diversity Web - Koala (November, 2004)
- Logan, M. (2001) Evidence for the occurrence of rumination-like behaviour, or myrecism, in the koala (Phascolarctos cinereus). Journal of Zoology, 255(1): 83-87.
- New South Wales National Parks and Wildlife Service - Koala (November, 2004)
IUCN (2009) Species and Climate Change: More than Just the Polar Bear. IUCN/Species Survival Commission. Cambridge, UK. Available at: