What is a Koala?
The Koala, Phascolarctos cinereus, is a tree-dwelling marsupial native to eastern and southeastern Australia. It is the only living member of the family Phascolarctidae. Koalas live mainly in eucalypt forests and woodlands, where they climb trees to feed, rest, and sleep. Their thick grey fur, large fluffy ears, broad nose, short tail, and strong limbs give them a distinctive appearance.
Adult koalas range from about 68 to 82 centimeters in body length. Their weight varies strongly across Australia, from about 4 to 15 kilograms. Southern koalas are larger and have thicker, browner fur, while northern animals are smaller and have shorter silver-grey fur.
The koala has an extremely specialised diet. It eats the leaves of selected eucalyptus and related trees, and the leaves provide both food and a large part of its water intake.
It sleeps for long periods.
Most of its active life takes place at night.
What does a Koala look like?
A koala has a round head, large furry ears, a broad dark nose, small eyes, and thick ash-grey fur. The chest and underside are lighter than the back in many individuals.
The body is compact and muscular. The front limbs are strong and equipped with hands adapted for gripping branches.
Each front foot has five digits, with two digits positioned opposite the other three. This arrangement gives the koala a strong grip while climbing.
The hind feet have another unusual feature. The second and third toes are joined, while the first toe is positioned separately.
The koala has only a short external tail.
Its thick fur also provides insulation during cold nights and protects the skin from rough tree bark.
How big is a Koala?
Adult koalas measure about 68 to 82 cm in body length according to the Australian Museum.
Adults weigh about 4 to 15 kg across the species' range.
Size changes with geography. The average weight of males in Victoria is about 12 kg, while the average male in Queensland is about 6.5 kg.
The largest animals occur in southern populations.
The smallest animals live in northern Queensland, where some adults weigh about 5.5 kg.
This geographic difference is one of the clearest physical patterns across the koala's range.
Where do Koalas live?
Koalas occur in Australia from Queensland through New South Wales and Victoria, with populations also present in southeastern South Australia and the Australian Capital Territory.
The species has a patchy distribution rather than forming one continuous population across eastern Australia.
Koalas live in eucalypt forests, woodlands, roadside vegetation, riparian areas, farmland trees, and connected patches of native vegetation.
They also use some urban and semi-urban areas when suitable food trees remain.
Australian government habitat guidance states that koala habitat can include remnant vegetation, non-remnant vegetation, roadside trees, paddock trees, and corridors that connect separate habitat patches.
Habitat connectivity matters because koalas travel between food and shelter trees on the ground as well as through trees.
What trees do Koalas eat?
Koalas are specialised leaf eaters. Their diet is based mainly on selected species of eucalyptus and closely related trees.
The Australian Museum reports that koalas use about 20 eucalyptus species out of more than 600 eucalyptus species found in Australia.
The exact preferred trees differ between locations.
Government conservation guidance reports that koalas use more than 400 tree species for food and habitat across their entire range, although the main food trees at one site can be limited to only a few species.
The chemical composition and water content of leaves affect which trees a koala chooses.
A koala therefore does not simply eat every eucalyptus tree it encounters.
How much does a Koala eat each day?
Koalas consume a large mass of leaves relative to their body size because eucalyptus foliage contains little energy.
Australian Museum sources report about 400 grams of eucalyptus foliage per day, while the Koala Genome Consortium reports that koalas can consume about 600 to 800 grams of leaves per day.
The difference reflects variation between individuals, food quality, body size, and the source used.
A large adult therefore can eat close to 0.8 kg of leaves in a day.
The leaves contain a high proportion of water, so feeding also supplies much of the koala's daily water requirement.
How does a Koala digest eucalyptus leaves?
Eucalyptus leaves contain tough fibre and chemical compounds that are toxic or unpalatable to many mammals.
The koala has a specialised digestive system that helps it process this difficult food.
Its caecum is extremely large compared with the body and contains microorganisms that help ferment plant material.
The koala also has specialised detoxification genes. Genome research identified expansions in the cytochrome P450 gene family, which helps the animal process plant chemicals.
Its teeth cut leaves into small pieces before the material enters the digestive system.
The koala also has a large bitter-taste receptor repertoire that helps it assess chemical compounds in eucalyptus leaves.
Does a Koala drink water?
Koalas obtain a large amount of their water from fresh leaves.
The Koala Genome Consortium reports that koalas preferentially eat leaves containing more than 55 percent water.
They also drink water directly when conditions require it.
During heat, drought, or other periods of low leaf moisture, access to free water becomes more important.
This is one reason why drought and changing rainfall patterns can affect koala habitat quality.
How does a Koala climb trees?
A koala climbs with powerful forelimbs and curved claws.
The two opposing digits on each front foot help it grip branches and trunks.
The hind feet also provide a strong grip, with the joined second and third toes forming a specialised structure.
Koalas can move down tree trunks head-first or descend carefully while gripping the bark with their claws.
They also travel between trees along the ground.
This ground movement creates a serious risk near roads and areas with domestic dogs.
How much does a Koala sleep?
Koalas spend up to about 20 hours a day resting and sleeping.
Their long resting period is linked to their low-energy diet.
Eucalyptus leaves provide limited energy, so the koala reduces energy expenditure by resting for long periods.
Most activity occurs during the evening, night, and early morning.
Feeding bouts are concentrated during the later part of the day and nighttime.
The animal often curls its body around a branch or sits in a fork where several branches meet.
Does a Koala migrate?
Koalas do not perform long-distance seasonal migrations like migratory birds.
They move between trees and habitat patches in search of food, shelter, mates, and suitable territory.
Home-range size changes with habitat quality. New South Wales wildlife authorities report home ranges from less than 2 hectares to several hundred hectares.
Movement increases during the breeding season.
Young males also leave their mothers and search for their own home ranges after becoming independent.
Road crossings increase during periods of higher movement, creating a serious collision risk.
What sounds does a Koala make?
Male koalas produce deep bellows during the breeding season.
The sound resembles a deep growl, snore, or guttural roar.
Females and young koalas produce higher-pitched squeaks and squawks during interactions or when threatened.
Male bellows can carry hundreds of metres through forest vegetation. A New South Wales government survey recorded bellows at distances of about 200 metres, while management guidance reports that the sound can carry up to 1 kilometre under suitable conditions.
Male vocalisations also contain information about body size. Research cited by the New South Wales government found a relationship between bellow characteristics and male size.
The sound therefore provides information to other koalas before they meet face to face.
When are Koalas most active?
Koalas are mainly nocturnal.
Activity increases during the evening and continues through the night.
They spend long periods feeding in trees and then move between feeding and shelter trees.
During breeding season, movement increases as males search for females and young animals leave their mothers.
New South Wales authorities identify August through February as a period of increased movement associated with breeding activity.
How do Koalas reproduce?
Koalas reach sexual maturity at about 2 years of age.
The breeding season varies between regions, but breeding activity is concentrated from late winter through summer in southeastern Australia.
Females produce one young in a successful pregnancy.
Twins are extremely rare.
Pregnancy lasts about 34 to 36 days.
The newborn is tiny, blind, and hairless when it is born.
It weighs about 0.5 grams and is only about 2 centimeters long in the documented measurements used by Australian government research.
How does a baby Koala grow?
The newborn koala crawls from the birth opening into its mother's backward-opening pouch.
Inside the pouch, it attaches to one of the mother's two teats.
The young remains in the pouch for about 6 months while its body develops.
After leaving the pouch, the young koala begins riding on its mother's back or resting against her body.
At around 7 months, the young has outgrown the pouch and spends more time outside it.
The mother introduces the young to eucalyptus leaves and also provides a special soft material called pap.
Pap contains microorganisms that help the young digestive system begin processing eucalyptus foliage.
Young koalas become independent at about 1 year of age.
How long does a Koala live?
Koalas can live for more than 15 years in the wild.
New South Wales wildlife information gives a broader lifespan range of about 10 to 20 years.
Longevity varies with sex, disease, food supply, predators, vehicle collisions, habitat quality, and local environmental conditions.
Females can live longer than males in some populations.
A koala living in a safe habitat with abundant food trees faces a very different set of risks from one living in a fragmented urban landscape.
Which animals prey on Koalas?
Adult koalas have few natural predators compared with their smaller prey species.
Large birds of prey, dingoes, and some large reptiles can threaten young or vulnerable koalas.
Domestic and feral dogs are a serious source of injury and death, especially when koalas travel on the ground.
Young koalas face greater danger because they are smaller and spend time outside the pouch on their mother's body.
Vehicle collisions are another major human-related source of mortality.
Are Koalas dangerous to people?
Koalas are wild animals and should not be handled without trained wildlife personnel.
They have strong claws and teeth.
A frightened or restrained koala can scratch or bite.
A koala sitting quietly in a tree is not looking for conflict with people.
The safest approach is to observe it without touching, feeding, or attempting to remove it from a tree.
What diseases affect Koalas?
Chlamydial disease is one of the major health problems affecting koala populations.
Two species of Chlamydia are documented in koalas: Chlamydia pecorum and Chlamydia pneumoniae.
Chlamydia pecorum is the more common cause of chlamydial disease in koalas.
The disease can cause infertility in females, blindness, weakness, and other health problems.
Koala retroviruses are also studied because they affect immune function and disease susceptibility.
Disease becomes especially serious in small fragmented populations where animals have fewer options for movement and reproduction.
How does habitat loss affect Koalas?
Habitat clearing removes food trees and shelter trees.
Fragmentation also separates koala populations into smaller patches.
Roads can cut through habitat and increase the risk of vehicle collisions.
Domestic dogs can attack koalas when they move across the ground.
Drought and heatwaves reduce leaf quality and water availability, while bushfires can destroy large areas of forest.
The Australian government identifies habitat loss, fragmentation, disease, vehicle collisions, dog attacks, climate change, and fire as important threats.
Are Koalas endangered?
The conservation status depends on the population and legal system being discussed.
Under Australia's federal environmental law, the combined koala populations of Queensland, New South Wales, and the Australian Capital Territory are listed as Endangered.
The Australian Museum also lists those populations as Endangered under the Environment Protection and Biodiversity Conservation Act 1999.
Victoria and South Australia have different population histories and legal classifications.
This distinction matters because the species does not face exactly the same conditions throughout its geographic range.
How many Koalas are in New South Wales?
A statewide baseline survey published by the New South Wales government in 2025 estimated about 274,000 koalas in New South Wales.
The reported 95 percent confidence interval was 231,000 to 320,000 animals.
The estimate came from more than 3,500 survey input sites, including more than 2,500 additional sites from other NSW Koala Strategy programs.
The field program used acoustic recorders and drone surveys to detect koalas across a large area.
This is a state-level estimate, not an estimate for the entire Australian population.
How does a Koala affect its ecosystem?
Koalas consume large quantities of eucalyptus foliage and therefore influence the vegetation they browse.
Their feeding transfers plant energy into the animal food web.
Koalas also provide prey for predators and scavengers after death.
By moving between trees, they connect different parts of a forest habitat during their daily activities.
Their dependence on mature eucalyptus vegetation also makes them useful indicators of the condition and connectivity of woodland habitat.
What makes the Koala different from other marsupials?
The koala is the only living species in the family Phascolarctidae.
It is also one of the most specialised leaf-eating marsupials in Australia.
Its digestive system, detoxification genes, teeth, taste receptors, and feeding behavior all support a diet dominated by eucalyptus leaves.
The animal's body is also adapted for tree life, with strong limbs, gripping digits, curved claws, and thick fur.
Its young complete a large part of their development inside the mother's pouch after a pregnancy lasting only about 35 days.
That combination of tree living, specialised leaf feeding, and marsupial reproduction makes the koala biologically distinct even among Australia's highly specialised mammals.
Sources:
- Australian Museum – Koala
- Australian Government DCCEEW – Koala
- NSW Government – Koala Native Animal Facts
- NSW Government – Koala Baseline Survey Technical Report 2025
- Australian Museum – The Koala Genome
- Australian Government – Identifying Habitat for the Endangered Koala
Source: Australian Museum – Koala
Photo source: Photo by the original photographer, via Wikimedia Commons. Check the file page for the photographer's name and the applicable license.
0 Comments