About Koalas

Despite being known to many as 'koala bears', the koala is not a bear! The koala is a tree-dwelling, folivorous (i.e. herbivore that eats mainly leaves) marsupial, found in scattered populations along the eastern seaboard of Australia—from west of Cairns in far north Queensland and as far south as Adelaide in South Australia. More isolated populations are also found on the tablelands of the Great Dividing Range and the western plains of Queensland and NSW. There are also populations relocated from the mainland to islands off Queensland, Victoria, and South Australia.

Due to habitat loss, the koala is now under threat, making it a sentinel animal for forest-dwelling species in this country. If the koala goes extinct, this may also precipitate the demise of other fauna and flora. Australia holds the shameful title of having the most significant number of mammal extinctions globally.

Koalas, a 'monogastric hindgut fermenter', not only have a large and complex digestive system to accommodate their diet of eucalypt leaves, their whole lifestyle has evolved around it! Starting with the selection of the right leaf type, the koala grabs a branch, then sniffs the leaf to check its quality (and toxicity level) prior to consumption. The leaf is broken off with a strong biting action, masticated (chewed), mixed with saliva to allow enzymes to begin the breakdown process, and then swallowed, before ending up in the stomach. Koalas “chew” their leaf in a methodical size-reduction process. Provided koalas have unworn, sharp interlocking cusp points on their molars; this is done efficiently. Aged koalas with worn, flat teeth cannot achieve an adequate leaf breakdown. The result is that such koalas cannot make use of their food and will likely starve to death.

We often get asked why we cannot “cure” some koala diseases and why we cannot give particular medications to koalas. Eucalyptus foliage is very tough and contains several chemical compounds designed to protect the tree. However, these compounds are quite toxic and would kill most animals (or people, for that matter) if they decided to eat them! Over millions of years, koalas, possums, and gliders have evolved the ability to live on a diet of eucalyptus leaves without suffering any issues with the deadly chemical compounds. So, how does a koala cope with the toxins? Koalas have developed an amazing liver that is quite big, has multiple lobes, and is very complex. Its job is to break down and excrete all those nasty compounds and eliminate them from the body via the urine. This liver works so well that a number of medications given to koalas are metabolised, broken down, and excreted before they have any chance of reaching the bloodstream and doing the job they are designed to do.

Even though koalas are seen as solitary animals, they actually live their lives as part of a dynamic, ordered hierarchical system. Each koala within the population lives in an individual home range. The home range size is dictated by the age, sex, and social standing of each koala, and it includes the number of trees, how far apart they are located, and what use they have. A koala occupies its home range for life unless pushed out through age, infirmity, or habitat removal. All home ranges within each population overlap at various points. Koalas also vocalise to each other, so communication for this animal is integral to daily life. The fittest, biggest, and most virile male koala is the alpha male. He occupies the best-quality habitat, which is usually the largest in size, and his territory overlaps the home ranges of 3–4 higher-ranking breeding females. Often, there is an alpha female, a healthy, fit, fertile, breeding koala who occupies prime habitat adjacent to the alpha male. It is crucial for all breeding females to secure good-quality habitat. Lactation, a process that demands a lot from an animal living on a low energy/low nutrient diet, underscores the urgency of preserving a breeding female’s range to sustain both herself and her young.

Koalas are found from north Queensland down into NSW, ACT, Victoria and South Australia. There are also a number of translocated populations on islands such as Kangaroo, St Bees, Raymond, Snake and Phillip Island. In 2022, the koala was officially listed as an endangered species. Severe droughts that occurred prior to 2019, followed by the 2019/2020 bushfires have had a major impact on the already declining koala populations. Until rigorous scientific survey work of how many koalas are left is completed, how many remain is still really unknown.

No! This is a common misconception, probably due to their teddy-bear like appearance. Koalas are not bears, they are tree-dwelling marsupials.

Most joeys emerge from the pouch at around 5-6 months, usually weighing anywhere from 450 grams upward (depending on where they come from). These young joeys sit hugging their mother's bellies or clinging to her back. Eventually, they will move onto mum's back full-time, until they are too heavy to be carried. Joeys will continue to feed from their mum until they're weaned - by 12 months of age.

The female reaches sexual maturity at the end of her second year or later and physical maturity at the end of her fourth year. Males – about 3 years sexual maturity and reach physical maturity at 4 years. It is not unusual for this to occur at a younger age as well.

The eucalypt leaf is very low in viable nutrients and koalas have a slightly lower body temperature and consequently a lower metabolic rate than most other mammals, to reduce the amount of energy expended per day. By sleeping 18-20 hours they conserve energy and their waking hours are used to feed, move and seek out mates during the breeding season. They do not get drunk on eucalypt leaves.

Koalas eat a number of species of eucalypt plus the flowers, buds, stems and bark. Koalas will also eat Allocasuarinas, Corymbias and Melaleucas so their diet is quite varied.

No, females can bellow also.

Age is mostly determined by tooth wear on the pre-molar and molar teeth (top jaw). Also skull length and crown to rump length in relation to their weight helps to determine whether they are sub-adult (not sexually active) or adult.

A koala can climb a tree expertly with considerable speed when necessary. On the ground they are also capable of reasonable speed over short distances.

In the Wild – coastal females 15-18 years; males 10-15 years. In harsher koala habitats, their life span can be less. In captivity both can live 15+ years. We hold the World Record for the Oldest Living koala - a female called “Birthday Girl” who died in 2011 at the age of 25 years.

Koalas sleep approximately 18 hours out of 24. This is an evolutionary strategy to conserve their energy as the eucalypt leaf is so low in nutrients/energy value.

An adult koala can eat up to a kilo of leaf over a 24 hour period. They often browse and eat for an hour or so, then sleep then feed again hours later.

There are approximately 900 species of eucalypt in Australia – in each region koalas are known to feed on anywhere up to 100 different species. Koalas normally have around 10 species that are their main preferred food source. They eat new and mature leaves, buds, flowers and at times bark but the bulk of their diet consists of leaves.

An adult koala can poo up to 200 pellets in 24 hours.

Domestic dogs are the main predators of koalas. Powerful Owls, Lace Monitors, and Wedge tail Eagles can also prey on Koalas. However, the number one predator of (ie threat to) koalas is the human species.

When the joey is about one year old it is no longer dependent on its mother and is fully able to fend for itself. Joeys are able to disperse from the maternal home range from 12 months on.

Adult koalas live in a home range and stay there for their entire lives unless age illness or a higher ranking animal removes them. Therefore adult koalas must be released back to their point of capture or very close by. It is very similar to humans owning a house and backyard.

Once joeys leave their mothers home range they become juveniles (like human teenagers) Juvenile male koalas that leave their maternal home ranges often struggle to find unoccupied habitat and tend to live in very poor country for the first few years until they are big enough to challenge bigger, older males. Juvenile females can also struggle to find unoccupied habitat but are usually accepted much more into new koala populations. These young koalas usually disperse well away into other new locations eventually finding new populations and new home ranges. This behaviour encourages good genetic diversity.

The size of a koalas home range is dictated by the age, sex, health and quality of the habitat. Koalas also belong to a social hierarchy in their population. For example coastal koalas in NSW are found in areas of good soil, high rainfall and in undisturbed habitat and have a high level of the quality food trees. Higher ranking adult male koalas’ home ranges can be up to 100 hectares for one animal, with higher ranking females’ home ranges being slightly smaller. Very old and unwell koalas tend to get pushed out of their home ranges and are often located in poorer harsher areas. Radio tracking of koalas over a 12 month period has found that the majority of koalas tend to partition their home ranges into summer and winter living in either end depending on the season. This makes sense – living in the cool gullies in summer and on the warmer ridges in winter. Many a home owner has said “our resident koala has been gone for months and he has just come back” – this is why. Mountain koalas found on the Great Dividing range are likely to have slightly larger home ranges and koalas on the western plains in harsher conditions often can have even bigger home ranges as their trees are more scattered.

The koalas diet is the same in both summer and winter as eucalypts are not deciduous. In spring and early summer, eucalypts have a big flush of growth with the young tips of the leaves being highly prized by koalas. Snow can fall in the mountain areas of NSW and Victoria with koalas usually moving down the slopes during winter getting well below the snow line.

Treating wild koalas that come into care can be very expensive. Costs include veterinary care, surgery, radiography (x rays) diagnostic imaging, pathology, drugs and daily care. The Koala Hospital has a number of paid staff who run the hospital along with paid leaf collectors who harvest fresh eucalypt leaf daily. The remainder of the large number of jobs required to run a successful hospital are done by the 200+ volunteers. The hospital could not survive without their wonderful work. The vast majority of the hospitals funding comes from the generosity of the public. The remainder comes from adopt a wild koala program and from sale of koala related merchandise in our shop.

The koala is admitted into the hospital and is given an initial examination depending on the reason for admission. If the koala has been hit by a car or attacked by a dog it gets immediate treatment. A koala suffering from a disease or an unknown issue is usually left to “settle” for the first 24 hours. The following day the koala goes under a general anaesthetic and is given a full examination which includes blood, pathology and sample collection, ultrasound, and then a treatment plan is put into action. Some koalas arrive in chronic severely ill states and are euthanised on welfare grounds as these koalas tend to be beyond treatment. If the koala does not have chronic advanced disease we will commence treatment. The current treatment plan for the disease chlamydia includes a six week course of medications and in some cases minor surgery. At the end of six weeks the koala is then left alone in the enclosure to recuperate for two weeks. We then re-anaesthetise the koala to see if the disease has returned (via a number of tests) and if ok, the koala is ear-tagged, microchipped and then released back to where it was picked up.

Each koala is weighed, sexed, aged and measured on admission. Every koala has its own admission card and patient data. Everything done to the koala is recorded both on their charts and on a data base. The data base holds full patient information and the data goes back to 1973. Once koalas are ready for release they are ear tagged and microchipped. If the koala is captured years later and brought into the hospital, staff can pull up the koalas chart and immediately know its clinical history. Some koalas are warmly called “repeat offenders” as they seem to continually be admitted to the hospital over their lifetime. The majority of these cases occur because these koalas have to continually battle with roads, dogs and all the human obstacles that urban and rural environments produce.

Fossil evidence has shown that ancestral koalas were part of the mega fauna (giant marsupials) millions of years ago. Modern koalas began to evolve and adapt to the drying of the Australian continent in line with the rise of the eucalypts. Consequently the koalas we see today have been in existence for a very, very long time.