Basic Koala Facts Phascolarctos cinereus

POPULATION SIZE

Koala population numbers have been an area of controversy with many differing opinions concerning estimated numbers and the survival status of the koala. Population sizes differ between localities and the process of data collection has proved to be expensive and time consuming. When analysing the survival status of the koala consideration must also be given as to the viability of existing population groups in terms of reproductive capacity and disease status. Currently the Australian Koala Foundation (a research body) has been compiling data through comprehensive research within known habitat areas.

The survival status of the koala varies between Australian States and locations within states, with listings varying from endangered to vulnerable. The koala is distributed along the east coast of Australia, ranging from north Queensland, New South Wales, Victoria and a small area within South Australia. There is no disputing the fact that koala population numbers are declining at a phenomenal rate. Habitat destruction is the single most important factor causing depletion of wild koala populations. The koala has disappeared from greater than 50% of its original range.

During the 1920's the koala was hunted for its fur. Numbers have been greatly reduced since then, from millions to a matter of mere thousands. The koala is now threatened, not by guns but by something more sinister and less obvious . . . DEVELOPMENT.

The habitat in which the koala lives and depends upon for its survival is being destroyed at a phenomenal rate. Destruction and fragmentation of habitat in many areas have resulted in crowding of the surviving koalas into smaller areas, and increased exposure to the dangers of road traffic and domestic dogs. There has also been a resultant increase in the spread and prevalence of disease in affected populations.

EVOLUTION

The closest relative of the koala is the wombat with which it shares some common anatomical features. It is believed that the koala and the wombat shared a common ancestor some 25 million years ago.

BEHAVIOUR

The koala has been described as comatose, cumbersome and lethargic. The koala, when within an established home range, is mostly arboreal, spending 20% of their time feeding, and 80% of their time sleeping. They spend less than 1% of their time grooming, traveling and finding a mate. Koalas become markedly active during summer which is their breeding season. Male koalas tend to wander around looking for a mate, hence the increased number of road and dog fatalities during breeding season.

Koalas display remarkable navigation skills. Rehabilitated koalas returned to an area away from their home range, have been known to travel several kilometers to return to their range. This can create problems when the koala has been relocated away from the area it was found in due to habitat destruction. Similarly, a koala who has been released in an unfamiliar area, will sometimes take months to select a home range that meets their approval. Factors affecting this decision includes existing koala populations and availability of food trees. Koalas prefer open eucalyptus forests and woodlands over dense forests, and prefer lowlands over highlands.

BREEDING

Both male and female koalas have their own distinct bellowing and grunting sounds which are used to attract a partner of the opposite sex. Koalas reach sexual maturity in their second year. Males usually establish permanent territories in their third or fourth year.

The female usually produces one young every one to two years, twins are rare. The female pouch enclosed two nipples, and opens towards the rear. Females give birth after a gestation period of 35 days.

The joey is born at less than 2 cm long and weighs about half a gram. Pouch life is 5-7 months with the joeys weaned during their last month. The mother excretes "pap" - a fluid from the caecum, which is ingested by the joey from the time of its first emergence. This is thought to assist the joeys in obtaining the natural microflora of the intestinal tract which is required to digest eucalyptus leaves.

The joey is nurtured in the pouch and then the juvenile is carried on the mothers back for several more months. The joey is usually fully weaned and independent at 12 months but has the potential to stay with its mother for two to three years.

The life-span of a wild koala is approximately 10-12 years, with koalas in captivity reaching ages of 15 to 18 years (oldest recorded koala in captivity).

DIET

Koalas need a wide variety of eucalyptus, and have a special preference for certain species of gum within certain regions. Distinctive seasonal preferences exist. There are over 120 different species of gum which are eaten.

Eucalyptus leaves have a high water content reducing the need for koalas to drink. However, despite popular belief, the koala does drink water. Eucalyptus leaves are high in fibre and low in protein. The leaves contain strong-smelling oils, phenolic compounds and sometimes cyanide precursors. The oils and phenolic compounds are detoxified in the koala liver. Koalas have an enlarged caecum (similar to the human remnant, the appendix) in which fermentation of the eucalyptus leaves occur. The mineral needs of the koala are met by the ingestion of small quantities of soil to supplement their diet.

WEIGHT

Males - weight range of 4.2 - 11.5 kg Females - weight range of 4.1 - 9.8 kg

Weight range is dependant on sub-species. The koala from Queensland and Northern New South Wales differs from the one which is native to Victoria. The northern koala is smaller and its fur is shorter and light grey in colour, whilst the southern koala has dark grey, shaggy fur. Victorian koalas can weigh up to 12 kilograms.

DISTINCT FEATURES

Male koalas can be characterised by large sternal glands which are used for scent marking. Koalas rub their chests against trees to mark their territory.

The koala has two thumb-like digits on the front feet with three fingers, and one nail-less thumb-like digit on the back feet with three fingers.

Koalas climb by grasping the trunk of a tree with the sharp curved claws of their front feet, and then bringing their hind feet up together in a bounding movement.

The koala has no canine teeth, and has only one pair of lower incisors in the lower jaw, and one well-developed pair in the top jaw.