Koala guide: why do they have big noses, what they eat, and the dangers they face
The koala is an iconic marsupial native to Australia, and was originally thought to be related to bears.
With its fluffy ears, grey-brown fur and large leathery nose, the koala is one of the world’s most famous marsupials. European scientists, who were unfamiliar with marsupials, originally thought they were related to bears.
Although a famous species from Australia, this distinctive mammal is actually only found on eastern and southeastern regions of the country – Queensland, New South Wales, Victoria, South Australia and ACT.
Our expert guide to koalas, by the Australian Koala Foundation, explains where they live, what they eat and why they may be at risk of extinction:
What does koala mean?
‘Koala’ is thought to mean ‘no drink’ in the Aboriginal language, although there are many different languages spoken by Aboriginal people throughout the country.
What is the scientific name of the koala?
The scientific name for the koala is Phascolarctos cinereus.
Phascolarctos is derived from the Greek words ‘phaskolos’ meaning pouch, and ‘arktos’ meaning bear, cinereus means ash coloured (grey).
Although some people mistakenly call them koala bears, koalas are not actually bears.
When the koala was given its scientific name by European scientists, the closest mammals they could relate the koala to at that time were bears.
How many subspecies of koala are there?
Among the scientific community there are differing opinions regarding the actual number of subspecies of koalas. Some are of the opinion there are three subspecies, while others claim there are only two and some ask are there any subspecies at all.
Currently the three named subspecies are:
- Phascolarctos cinereus adustus from northern Queensland
- Phascolarctos cinereus cinereus from New South Wales
- Phascolarctos cinereus victor from Victoria
The New South Wales subspecies being the most debated.
The taxonomy of these three subspecies is based on differing physical characteristics. The main differences are that koalas in the south are larger than those in the north and also their fur differs in that it is thicker, fluffier, and often darker. Because the winters in the south are colder than those of the north it is likely that the koalas either evolved or adapted to the climatic conditions.
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The koalas in between fall somewhere in between these two different sets of characteristics. The distribution of the three subspecies has not yet been defined but has been delineated by the state boundaries.
What is the closest relative to the koala?
There are around 200 marsupial species found in Australia, including bilbies, kangaroos (including tree kangaroos), numbats, phascogales, quokkas, quolls, Tasmanian devils, wallabies, and wombats.
The closest relative to the koala from the Australian marsupials is the wombat.
What is the koalas’ habitat and their distribution?
‘Habitat’ refers to the types of bushlands that Koalas like to live in. They are found in a range of habitats, from coastal islands and tall eucalypt forests to low inland woodlands.
Today they do not live in rainforest, although it is thought that millions of years ago the ancestors from which today’s Koalas evolved lived in the rainforests which covered much of Australia at that time.
Koala populations only occur if suitable habitat is available. The two most important factors which make habitats suitable are:
- The presence of tree species preferred by koalas (usually eucalypts, but also some non-eucalypts) growing in particular associations on suitable soils with adequate rainfall and
- The presence of other Koalas.
Research shows that socially stable Koala populations occur only when there are primary (or favourite) tree species present.
Even if a selection of tree species known to be used by koalas occurs within an area, it will not support a koala population, or at least the koala population will not use it, unless one or two favourite species are present.
Koalas live in societies, just like humans, so they need to be able to come into contact with other koalas. Because of this they need to have areas of suitable eucalypt forest which are large enough to support a healthy koala population and to allow for expansion by maturing young koalas.
Koalas are found in Queensland, New South Wales, Victoria, South Australia and ACT.
Their range extends from the Atherton Tableland west of Cairns in Queensland to islands off the coast of Victoria and South Australia in the south, and west to central and western Queensland, New South Wales, Victoria and ACT.
Populations are fragmented throughout this range and many populations are seriously at risk.
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What is the life span of the koala?
When in the wild with an undamaged habitat the koala can live up to 10 years.
This can be greatly reduced in areas with damaged habitat, such as suburban areas, to a few years or even months due to the dangers posed by cars and dogs.
The male tends to have a shorter life span than the female, due to the stress caused by fights during the breeding season, and during this time they will move around more in search of a mate putting them in increased danger from cars and dogs.
How big are koalas?
Koalas from the southern region of Australia are considerably large than those from the north, also the male will be larger than the female.
- Male length: 72 - 82cm
- Male weight: 9.5 - 14.9kg
- Female length: 68 - 73cm
- Female weight: 7 - 11kg
- Male length: 67.4 - 73.6cm
- Male weight: 4.2 - 9.9kg
- Female length: 64.8 - 72.3cm
- Female weight: 4.1 - 7.3kg
What are the main physical features of the koala?
Koalas have a large leathery nose. (Further details later in article)
Like the nose, the koalas’ ears are large in relation to the size of their head and provides a keen sense of hearing.
Which is a necessity for their socialisation with other Koalas, as they can live in populations where each Koala lives large distances apart.
In relation to the size of the koalas’ other sensory features their eyes are quite small. Koalas do not particularly have highly developed eyesight.
The koala has one of the smallest brains relative to body weight of any mammal, which may be an adaptation to its low-energy diet (brains consume a lot of energy).
The front and hind limbs of the koala are almost equal in length and much of the koala’s climbing strength comes from the thigh muscle, which joins the shin much lower than in many other mammals.
With rough pads on both their palms and soles and front and hind paws having long sharp claws, they are specifically adapted for gripping and climbing.
Each paw has five digits; the front paws have two digits opposed to the other three (rather like that of the human fingers and thumb) allowing them to move in opposition to the other three.
On the hind paws the second and third digits are fused together forming a double-clawed digit, this is used for grooming.
The largest digit of the hind paw does not have a claw.
Koalas are the only other animal besides primates to have individual fingerprints. A study comparing koala and human fingerprint showed they were easily distinguishable, but there were some similarities.
The fur of a koala is thick and woolly which provides protection to both high and low temperatures, it also offers protection against the rain.
The fur is thicker on the rump of the koala, this acts as an inbuilt cushion for the hard branches it sits on.
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What are the differences between male and female koalas?
The male adult koala is larger than the adult female, only the female has a pouch. The external genitalia are visible on a male Koala.
The most visible difference is the mature breeding adult male has a dark brown scent gland in the middle of its white chest.
Female and young pre-breeding males do not have this scent gland.
The male koala is referred to as a buck and the female as a doe.
Why do koalas have such a large nose?
The koala has a large leathery nose making it one of its most noticeable features. Koalas have a highly developed sense of smell, enabling them to detect the varying levels of toxins within the eucalyptus leaves.
Koalas leave scent warnings on trees, so other koalas need to be able to detect this.
It is thought that the koala is born with a well-developed sense of smell.
Does the koala have a tail?
Koalas do not have external tails.
However, vestiges of a tail are still present in the skeletal structure of the Koala, indicating that at some time in its evolutionary history an external tail was present.
What do koalas eat?
The koala is the only mammal, other than the greater glider and ringtail possum, which can survive on a diet of eucalyptus leaves.
Eucalyptus leaves are very fibrous and low in nutrition, and to most animals are extremely poisonous. To cope with such a diet, nature has equipped koalas with specialised adaptations.
The koalas’ digestive system is especially adapted to detoxify the poisonous chemicals in the leaves
The koala has a fibre-digesting organ called the caecum, this organ is also found in other animals including humans, however the caecum of the koala is very long (up to 200cm).
The caecum contains millions of bacteria which breaks down the fibrous eucalyptus leaves enabling the koala to absorb them, although they are still only able to absorb 25% of the fibre.
The water content from the leaves is also absorbed meaning koalas rarely have the need to drink water.
A koala will eat between 200 and 500 grams of leaves each day.
How long do koalas sleep?
Koalas usually sleep between 18 to 22 hours. They sleep a lot to conserve energy as their diet requires a lot of energy to digest. They sleep in the branches of trees.
Koalas are mainly nocturnal, although they sometimes move about during the day.
What sound do koalas make?
Koalas also communicate with each other by making a range of noises.
The most startling and unexpected of these in such a seemingly gentle animal is a sound like a loud snore and then a belch, known as a ‘bellow’.
What is unusual about the koala pouch?
The pouch is actually situated in the centre of the female’s abdomen and the opening faces straight outwards, rather than backwards.
However, the pouch opening is towards the bottom of the pouch, so when the joey is larger and puts its head out of the pouch it can appear that the pouch faces backwards.
The pouch has a strong sphincter muscle at the opening to prevent the joey from falling out.
How often do koalas give birth?
The breeding season for koalas is approximately August to February. Females generally start breeding at about three or four years of age, usually producing one offspring each year.
However, not all females in a wild population will breed each year; some produce offspring only every two or three years, depending on factors such as age and habitat quality.
The gestation period for the koala is only 35 days, the new born is tiny measuring roughly 2cm and weighing less than 1g.
They are hairless, blind, without ears, and look like a pink jellybean.
In the average female’s 12-year life span, she may produce five or six offspring over her lifetime.
How long does the young koala stay in the mother’s pouch?
As with other marsupials the young of the koala is called a joey.
The joey stays in its mother’s pouch for about 6 or 7 months, drinking only milk.
Before it can tolerate gumleaves, which are toxic for most mammals, the joey must feed on a substance called ‘pap’ which is a specialised form of the mother’s droppings that is soft and runny.
This allows the mother to pass on to the joey special micro-organisms from her intestine which are necessary for it to be able to digest the gumleaves.
The joey feeds on this for a period of up to a few weeks, just prior to it coming out of the pouch at about 6 or 7 months of age.
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Chewing Koala © Australian Koala Foundation
Do koalas have any predators?
Natural predators of the koala do not make a significant impact on wild populations.
They include goannas dingoes, powerful owls, wedge-tailed eagles, and pythons, all of which are most likely to prey upon juvenile Koalas.
What are the main threats to the koala?
Koalas are listed as Vulnerable on the IUCN Red List.
The main threat is loss of habitat. Clearing of the land for expansion of human settlement, for example, for agriculture, housing, mining, forestry, shops, factories and roads.
The deforestation of the eucalypt forests affects not only the koala but all wildlife:
- Loss of habitat
- Increased disturbance by humans
- Injury or death from traffic
- Injury or death from dogs
- Garden pesticides getting into waterways
- Increased competition for food, due to overcrowding
- Increased competition for territory, due to overcrowding
- Increased stress, making them more susceptible to disease
Cars and dogs
Over 4000 koalas are killed by cars and dogs each year, as more habitat is cleared for housing estates the situation becomes more serious.
The chlamydia organism causes four common diseases in the koala:
- Urinary tract infections
- Reproductive tract infections
Conjunctivitis can cause blindness, reproductive tract infections can cause infertility in the female.
Koalas also suffer from a range of cancers like leukaemia and skin cancers.
Dieback is when trees begin to gradually die, this can be caused by changes in the balance of the ecosystem caused by such things as water levels, change in the nutrient in soil, salination of the soil.
Koalas are at great risk from bushfires. If a koala population is living in an area of bushland which is surrounded by development, the whole colony could be wiped out in a single fire.
In 2020 major bushfires devastated an area that covering a region of New South Wales, Victoria and South Australia equivalent to over two-fifths of the UK.
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Koala Population Estimates 2021 | Australian Koala Foundation
Koalas in crisis
Koalas are in freefall, with possibly as few as 32,000 remaining in the wild, according to figures released by the Australian Koala Foundation, which show that the country has lost nearly a third of its koala population over the last three years.
As the climate crisis intensifies in Australia, koalas are under increasing pressure from bushfires, heat waves and a lack of available drinking water. The destruction of koala habitat is also a major factor in their decline.
“Over the past few years, we have seen huge land clearance, particularly across New South Wales and South-East Queensland, for farming, housing development and mining,” says Deborah Tabart, Chair of the Australian Koala Foundation.
The Australian Koala Foundation is calling for urgent action to stop land clearing in prime koala habitat and for a Koala Protection Act.
This article originally appeared in BBC Wildlife, and was written by Simon Birch
Main image: Koala resting in trees near Brisbane, Australia. © Michael Siward/Getty
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