What do they look like?
The koala is a well-known and popular animal, endemic to Australia but recognised around the world. It is a tree-dwelling marsupial with large furry ears, a prominent black nose, long sharp claws adapted for climbing and no tail. Fur colour varies from pale grey in north Australia to grey-brown in the south.
Koalas also vary in size across their range. Adult males weigh between 4 to 14 kilograms and adult females weigh between 4 to 10 kilograms.
Despite being called 'koala bears' for many years, koalas are marsupials. While bears give birth to well-developed young, newborn koalas are tiny enough to fit on your thumbnail, and are raised in their mother's pouch.
The closest relative of the koala is the wombat - both animals have pouches which open towards the rear. This is fine for the wombat, but koalas need strong muscles ringing the pouch to keep their young from falling out.
What do they sound like?
During breeding, males advertise with loud snarling coughs and bellows. Koala mating songs range from the pig-like grunts and growls of the males, to the high pitched trembling sounds of the females.
Research published in The Journal of Experimental Biology and publicised by ABC Science indicates there is a variation in the bellows that correlates with the size of the male – this may be used to intimidate rivals or attract mates.
Where do they live?
Koalas live in eucalypt woodlands and forests. Home range size varies according to quality of habitat, ranging from less than two hectares to several hundred hectares.
Koalas are found between south-eastern South Australia and Queensland, but only where enough suitable trees have been left. The largest koalas weigh over 10 kilograms and are found in Victoria, while the smallest live in North Queensland and weigh only 5.5 kilograms.
In NSW, koalas mainly live on the central and north coasts, with some populations west of the Great Dividing Range, on the south coast and on the southern tablelands. Most populations live in isolated habitats and many areas in which koalas are most abundant are subject to intense pressures.
What do they eat?
A koala eats about half a kilogram of leaves each day. Koalas are fussy eaters, choosing most of their food from a few varieties of eucalypt. Around Sydney, red gums and mahoganies are their most favoured trees. In northern areas of the State, tallowwood and forest red gum are important, manna gum tops the bill in the south, and in the west koalas prefer river red gum and ribbon gum. They use a variety of other trees for shelter during the day and in heatwaves or storms, including paperbark, she-oak, brush box and acacia trees.
Gum leaves are not the easiest things to digest - they are tough and contain oils which can be poisonous. To cope with such an unusual diet, koalas have a long, thin tube like an appendix branching out from their intestines. This tube grows to a length of two metres. It probably helps with digestion, although its exact function remains a mystery.
As their food contains little energy, koalas conserve energy by sleeping for most of the day and looking for food in the evening. Koalas do not normally drink water, as they get sufficient water by licking the dew from leaves.
How do they get about?
With huge claws and strong muscles, koalas are able to hold on tightly to trees. They have two thumbs and three fingers on each front paw, which makes their grip more even on each side of a branch. They also have a clawless big toe on their hind legs, which allows them to grip with their hind feet as well. Two of their hind toes joined together form a handy two-toothed comb, used for grooming fur and removing ticks.
Breeding and life cycle
Koalas live for between 10 and 20 years, and generally breed between September and February. Female koalas can breed from about two years of age, and have a gestation period of about two months, producing one young koala a year, and on rare occasions they may produce twins.
A newborn koala is tiny, blind and hairless. Dragging itself into its mother's pouch, it attaches itself to one of her two teats. By about seven months, the baby has outgrown the pouch. It rides on its mother's back, or rests against her chest as she drowses in the fork of a tree. During this time, the young koala samples gum leaves. When the young koala is about one year old, its mother is able to mate again.
Often, young male koalas will be driven off by older males. To survive, they must find a suitable area which is not already occupied by other dominant male koalas. Koalas are generally solitary, although they do have a social structure based on a dominant male. They rest for most of the day - at night they feed and move between trees, and sometimes along the ground.
Why are they special?
- People have a close affinity with the koala.
- Koalas benefit the Australian economy – it has been estimated that they create over 9,000 jobs and contribute between $1.1 billion and $2.5 billion per year to tourism in Australia.
- Koalas feature in many Aboriginal dreaming and creation stories and are a totemic species.
- Although the koala’s Latin name, Phascolarctos cinereus, means ‘ash-coloured pouched bear,’ the koala is not a bear but a marsupial whose closest relative is the wombat.
- Koalas are one of the few animals, along with ringtail possums and greater gliders, that feed exclusively on eucalyptus leaves.
The koala has suffered a dramatic decline in numbers and distribution since the arrival of Europeans. Surveys in New South Wales indicate that since 1949, populations of koalas have been lost from many localities. Most populations in NSW now survive in fragmented and isolated habitat and many of the areas in which koalas are most abundant are subject to intense and ongoing pressures, in particular loss, modification and fragmentation of habitat.
The koala is listed as 'vulnerable to extinction' under the Threatened Species Conservation Act 1995 because of declining numbers and the ongoing pressure of threats. Such listing gives the species more protection and attention, and means proposals for development that will affect koala habitat are rigorously assessed.
In April 2012, koala populations in Queensland, NSW and ACT were listed as vulnerable to extinction under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999.
Threats to koalas include:
- loss, modification and fragmentation of habitat
- disease (Chlamydia)
- vehicle strike
- intense prescribed burns or wildfires that scorch or burn the tree canopy
- predation by roaming or domestic dogs
- heat stress through drought and heatwaves
- human-induced climate change.
The most significant disease in koala populations is Chlamydia, a highly infectious bacterial disease. Koalas in NSW carry Chlamydia pathogens but do not always show clinical signs of disease. They have symptoms such as conjunctivitis and urogenital tract infections when they are stressed by:
- loss of habitat
- harassment by predators
- starvation or malnutrition
The disease weakens koalas, making them more vulnerable to death from other causes, particularly dog attack and severe weather conditions. Trials are under way in Queensland to test whether a recently developed vaccine can protect koalas from Chlamydia.
As koalas generally give birth to one young a year, their populations cannot increase rapidly. However as mortality is also low, populations can double in three years in the absence of Chlamydia and other threats. Local extinctions are possible where:
- there is loss of fertility due to Chlamydia
- there is habitat fragmentation
- there are high rates of mortality due to one or more localised threats, e.g. vehicle strike in urban areas, heat waves, fires.
Loss, modification and fragmentation of habitat
Trees help protect koalas from predators and harsh weather, but most importantly they provide them with food. Koalas prefer forests growing in better soils, and most of these forests have been chopped down for agriculture and housing. This has left many koalas living in small, isolated patches of poor quality forest.
If a particular patch of forest is fully occupied and they have to leave the area, young koalas may have to cross open spaces, including roads. They can be run over by cars, and many are attacked by dogs (which means that large dogs living in areas of koala habitat should be carefully supervised). A lack of suitable food and the stress of living in a fragmented environment may also make them more susceptible to disease.
Koalas used to live in much of coastal and inland Queensland, New South Wales, Victoria and south-eastern South Australia. However, by the 1930s they were present in less than 50% of their previous distribution.
Early European settlers saw the koala as a scientific oddity and a valuable trading commodity – about 200 million koala furs were exported to Britain and the United States in the late nineteenth and early twentieth centuries, which led to the extinction of the animal in some areas.
A survey of koalas in NSW in 1986–87 found that they had disappeared from 50–75% of their historical range. Due in part to protective legislation and the cessation of hunting, koalas have returned to many parts of their former range – in New South Wales and Queensland naturally and in Victoria and South Australia due to being reintroduced.
Saving our Species is developing a 5-year project for the conservation of koalas in NSW. The Saving our Species Iconic Koala Project will be released for public exhibition in the coming months.
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Page last updated: 25 October 2016