Koalas are arboreal (tree-dwelling) marsupials, and the only member of the family Phascolarctidae, with a distribution over most of the eastern part of Australia, although the populations are largely fragmented. They are found from the Eyre Peninsula, and Kangaroo Island in SA, to the southern-most parts of Victoria (including populations on French, Snake and Raymond Islands) up to the southern edge of the Atherton tablelands in Northern Queensland. They are found in sclerophyll forests and woodland areas.


Koalas are folivors and feed on a diet that is nearly entirely made up of Eucalyptus, but they will occasionally eat non-Eucalypt species such as Brush Box (Lophostemon confertus), Allocasuarina sp. and Melaleuca sp. There are over eight hundred species of Eucalyptus in Australia and koalas will eat around forty to fifty of those. In most areas koalas will have access to around seven species of eucalyptus. Soil type and seasons will have a major impact on whether leaf in a certain area is palatable, so whilst they may favour a eucalyptus species from one area they may not eat it if it comes from a different soil type or the season is not right. They consume a mix of new and old growth.

Some of the main browse species in South-east Queensland are:

  • Blue Gum (Forest Red Gum) Eucalyptus tereticornis
  • Tallowwood E. microcorys
  • Grey Gum E. propinqua, E. punctata and E. major
  • River Red Gum E. camuldulensis
  • Swamp mahogany E. robusta

Secondary browse species include:

  • Spotted Gum E. maculata
  • Gum-top Box E. molucana 
  • Red stringybark E. resinifera
  • Narrow-leafed Ironbark E. crebra
  • Narrow-leafed Redgum E. seana
  • Flooded gum E. grandis
  • Poplar Box E. populnea
  • Scribbly Gum E. signata
  • Sydney Blue Gum E. saligna

Home Range

Koalas are basically solitary animals and live in relatively well-defined home ranges. In breeding aggregations these home ranges abut or partially overlap adjacent home ranges of other individuals. Home ranges will most often consist of an alpha male whose home range then encompasses a number of female’s home ranges, each female will have her defined area within this range, with most overlapping that of another female. . You will often find a non-dominant male or younger male whose home range will slightly overlap one corner or section of the alpha male’s territory.

Koalas tend to be faithful to their home ranges and will attempt to return if moved out of them. The relocation of older animals that are healthy, in good body condition and who are coping well with their current home range should be discouraged unless the destruction or loss of habitat is a recent event. In cases where this does occur a number of factors need to be taken into consideration and permission from appropriate authorities obtained.

The size of a koala’s home range is highly variable and depends upon the age, sex, forest type, soil quality, reproductive status, area available and presence of other koalas and breeding aggregations. In more arid habitat that has less dense forest areas or woodland, the home ranges tend to be larger than those of koalas living in coastal Eucalypt woodlands.

Koalas in some areas can have a very small home range if the koala density in the area is heavy, particularly with dominant males. Fences, roads, abundance and access to food trees also play a part in this.


The koala breeding season in Queensland extends from around August through to January with most young born over the summer months although some have been reported as late as April.

Usually a single joey (twins are rare) is born after a 34-36 day gestation when the joey makes its way from the birth canal to the pouch. The joey remains in the pouch until it is approximately 5.5 to 6 months of age or between 300 and 450gm. During the next few weeks it will become more adventurous and will emerge fully at around 6 to 6.5 months of age after pap feeding. Once they reach 8 to 8.5 months old or around 700gm they are too big to return to the pouch and will become what is termed ‘back young’ until they are around 12 months old. Koalas are usually excellent mothers and are highly tolerant of their energetic young. Complete independence from the mother occurs between 12 to 18 months of age.

Female koalas have a pouch which contains 2 teats. Koala joeys when they reach the pouch after birth will attach to one teat, This teat will be the only one they will feed from until weaning.

The time of pouch emergence is when the highest incidence of infant mortality occurs.

Between 18 months to 2 years of age juveniles generally move away from their maternal home range to find their own home range, with females often choosing to set up home ranges that overlap their mothers or settling not too far away.

During this time juveniles may move around a great deal and are susceptible to dog attack, car accidents and misadventure.

Sexual maturity is from around 2 years onwards.

Koalas have few natural predators other than man but young can fall victim to birds of prey, pythons and dogs, both wild and domestic, with adult koalas most come to grief because of motor vehicles, domestic dogs and disease.

The male koala has a prominent sternal gland which results in the fur in this area being stained an orange/brown colour. This gland often becomes more noticeable as the male gets older and is more prominent in breeding season when both the gland and the emulating odour are both present.

Male koalas can emit a very loud bellow vocalization, which can sound quiet eerie if you happen to be bushwalking in the dark. Young males sound like a squeaky frog as they test the noise they need for the future. All koalas have the ability to vocalize and emit different sounds to express different things.

Natural History

The Queensland female koala has a weight range of between 4.1kg and 7.3kg with an average of 5.1kg. Although there is the occasional 8kg to 9kg female recorded, they are not common.

The Queensland male koala has a weight range of between 4.2kg and 9.1kg with an average of 6.5kg. Koalas in New South Wales and Victoria have a much heavier average weight than Queensland koalas with Victorian koalas being the heaviest of all the states.

The dorsal fur of the koala is the most insulated of any marsupial found to date and in the past was heavily sought after for the fur industry. The ventral surface has half the density of the dorsal surface, and is more reflective of solar radiation. In cold weather koalas will curl into a ball with the dorsal fur providing effective insulation from the cold and rain. In warmer months they will often sit sprawled out with their ventral surface exposed to the sun which has a cooling effect for them. Panting is the main means of evaporative cooling in high temperatures. Although some sweat glands exist on the hand and foot pads this is not an outlet for overheating. In extremely hot conditions, particularly in the Brigalow belt of Queensland, koalas have been known to seek refuge in caves, tree hollows and wombat burrows.

How can I tell if a koala is sick or injured?

If you live in an area where you frequently see koalas, it makes good practice to keep an eye out for any signs of injury or disease. The sooner a sick koala receives veterinary treatment, the better its prognosis.

The following table provides a guide of the differences between a healthy and sick koala.

Healthy Koala Sick or Injured Koals


  • Should be dense, grey and uniform
  • Female koalas with back young or recently weaned young may show patchy fur loss and dark grey or brown patches around the shoulder region.


  • Brown, sparse, coarse or tufted in appearance
  • Hair loss
  • Scaly, encrusted skin
  • Any signs of wet fur which might indicate saliva from a dog

Body Condition

  • should be well nourished and slightly pot-bellied
  • pelvic bones and spine should not be discernible
  • body condition can hard to assess distantly

Body Condition

  • hollowness between the ribcage and pelvis
  • pelvic bones and spin easily discernible


  • Bright, alert and responsive to disturbance
  • Ears should become erect when disturbed


  • Unresponsive
  • Able to approach closely


  • Should be clear, bright and free of discharge
  • Should have no fur loss around the eyes


  • Crust formed over eyes
  • Inflammation around the eye
  • Pus forming in the eye

Vent and Rump

  • Bottom should be clean, white, dry and free of dirt or dark brown stains

Vent and Rump

  • Wet bottom
  • Dark stained bottom (brown colour)


  • Healthy koalas should be up a tree during the day.
  • If on the ground, they should move away when approached.


  • Sleeping on the ground
  • Sitting at the base of a tree for a period of time
  • Does not move away when approached

Mouth and Nose

  • Should be clean and free of discharges or drooling

Mouth and Nose

  • Discharge
  • Drooling


  • Breathing should be barely discernable


  • Open mouth breathing
  • Panting
  • Labored or noisy breathing

Koalas, like most wild animals, mask their signs of illness well. If you are in doubt about whether a koala is sick, check up on it a number of times over a day or so. Note however that some koalas will return to the same tree to sleep each day so checking during the night is also important.

Healthy koalas tend to move around within an area from night to night, whereas sick koalas may stay in the same tree for prolonged periods.

Some koalas will look extremely healthy but may be very ill. The onset of some diseases or injuries from accidents such as car hits and dog attacks can be sudden.

Capture and Handling

Koalas have strong razor-sharp claws that are capable of causing severe injuries particularly to the face. They also bite – hard. Although they may appear docile, they are capable of lashing out very quickly when provoked or threatened. Koalas that do not react to handling are usually very sick. They should all be handled with care.

We do not recommend that anyone attempt to capture or handle a koala unless they have been specially trained to so do.

Report all sick and injured koalas to WILDCARE or to your local wildlife care organisation so that a specially trained volunteer can assess and capture the koala, if required.

Common Diseases and Injuries of Koalas

Unfortunately koalas are prone to a number of diseases and injuries.

Some diseases of wild koalas are easily recognizable while others are only be detectable through a thorough veterinary assessment by an experienced koala veterinarian.

Koalas mask their illnesses very well – sick koalas are very sick koalas.

A serious, debilitating and sometimes fatal disease caused by two different strains of the bacterium Chlamydia. It commonly causes ocular and urogenital disease manifested by keratoconjunctivitis (pink-eye), infertility and urine staining of the rump caused by cystitis (dirty tail).

Chlamydial disease is often complicated by secondary infections with other bacteria and fungi and is exacerbated by a number of factors including chronic stress, poor nutrition and immunosuppressive diseases.

Spread of the disease is almost certainly by the venereal route, and possibly also by close contact and flies.

Koalas suffering from Chlamydia have a good chance of recovery if they are treated in the early stages of the disease.

Manifested by weight loss, depression, dehydration and sometimes, concurrent disease. This condition is common in koalas, where the loss of habitat is having a tremendous impact on their ability to survive.

There is good evidence for the existence of a pathogenic retrovirus that infects koalas. It may cause bone marrow suppression leading to anaemia and immunosuppression, lymphoid neoplasia and other cancers. It may also cause an AIDS-like syndrome. With the exception of lymphoma, which causes enlarged lymph nodes, most of these diseases can only be detected by careful interpretation of blood tests by an experienced wildlife veterinarian.

Mostly caused by road trauma and dog attacks, but can also be from tree felling, cattle injuries or misadventure. All koalas that are suspected of trauma MUST come into care and receive immediate veterinary attention, which includes appropriate pain medication.

Often the injuries associated with such trauma are not clearly visible. Even if the koala has managed to climb a tree, these animals must be reported promptly so that they can be safely retrieved and provided with urgent veterinary attention.

Trauma from car hits often results in fractures and internal bleeding.

Trauma from dog attacks can result in severe damage to muscle and underlying tissues, this type of damage can often go undiagnosed as it can appear superficial on the surface. Aggressive treatment is required in these circumstances, antibiotics and fluid therapy is required as soon as possible to help prevent the risk of infection. Even if a dog has only “nipped” a koala, it still requires immediate veterinary attention.

Rescuing and Caring for Koalas

Koalas are classified as a ‘specialised species’ under the Nature Conservation Act 1999 and as such, you need to hold a special Rehabilitation Permit issued by EHP to care for sick, injured or orphaned koalas.

Rescuing koalas requires the use of specialised rescue equipment including flagging poles, nets, koala traps and large transport cages.

If you are interested in learning how to rescue koalas, enrol to complete a koala workshop through WILDCARE.

Caring for injured and orphaned koalas is very time consuming and is generally undertaken by wildlife rehabilitators that have several years’ experience with caring for wildlife.

For more information on koalas, check out the following brochures and information sheets:-