Koalas are marsupials that are native to the Australian continent. Their scientific name, Phascolarctos cinereus, is derived from several Greek words meaning pouch bear (phaskolos arktos) and having an ashen appearance (cinereus). They are often called koala bears, but that is scientifically incorrect, since they are not bears. Their most distinctive characteristics are their fluffy ears and their spoon shaped noses. Koalas are most often found in the southern and eastern areas of the continent.
Fast Facts: Koala
- Scientific Name: Phascolarctos cinereus
- Common Names: Koala bear
- Order: Diprotodontia
- Basic Animal Group: Mammals
- Distinguishing Characteristics: Spoon shaped noses and fluffy ears
- Average Size: 2 - 3 feet in height
- Average Weight: 20 - 25 pounds
- Life Span: 12 - 18 years
- Diet: Herbivore
- Habitat: Forests and woodlands in Australia
- Population: Approximately 100,000 - 500,000
- Conservation Status: Vulnerable
- Fun Fact: Koala babies, called joeys, are blind at birth.
Koalas are best known for their round body appearance and their distinctive ears and nose. Like other marsupials, females have a permanent pouch for raising young. Koala pouches are positioned in the lower portion of a koala's body. The pouches open outward so a joey (baby) can climb into it from the birth canal. When a joey is present, its mother uses her sphincter muscles to make sure that the pouch is closed so that her baby won't fall out.
Koalas are uniquely suited for living their life in trees. Their paws help them to expertly grip and climb trees. The pads on their paws are very rough and help with their gripping ability. Each paw has five digits. The front paws have two digits that are opposed to the remaining three digits. This helps with their grip strength while climbing. Their fur, which is typically light gray or brown, is very thick and helps to protect them from both low and high temperature conditions.
Koalas are usually between 2 to 3 feet in height and can weigh up to approximately 25 pounds. Other physical characteristics of koalas are their lack of a tail and their long limbs for their body size. Their tail is considered a vestigial structure and is thought to have been lost due to evolutionary adaptation. They also have one of the smallest brain-to-body-weight ratio of any mammal and are not considered to be very intelligent creatures.
Habitat and Distribution
Koalas live in Australia in a variety of habitats from forests to woodlands. Their preferred habitats are forests composed of eucalyptus trees, where they are able to survive very high up in the trees. They are found in New South Wales, Queensland, Victoria, and South Australia.
Diet and BehaviorThis is an image of a koala eating eucalyptus in Queensland, Australia. georgeclerk/E+/Getty Images
The koala's diet consists mainly of eucalyptus leaves. They can eat a pound to two pounds of leaves a day and have developed specialized structures to aid in the digestion of so much foliage. Their intestines (caecum) can be 7 to 8 feet in length. Although eucalyptus can be poisonous to most animals, symbiotic bacteria are present in their intestinal pouch which break down the toxic substances like tannins found in eucalyptus leaves.
Generally speaking, koalas are solitary animals. Each koala has a "home range" of a number of eucalyptus trees in a given area. The size of this range can vary depending on the koala's "status," sex, and habitat quality. A dominant male for example, may have a comparatively larger area. Ranges for different koalas overlap, which allows koalas to have social interaction with others in their vicinity.
Koalas are mostly nocturnal. They are not very active animals and spend a large portion of their time sitting or sleeping to conserve energy. Eucalyptus leaves are difficult to digest and require a considerable amount of energy expenditure. Koalas can sleep for up to 17 to 20 hours a day.
Reproduction and OffspringA koala joey remains in its mother's pouch for the first months of its life. Bruce Lichtenberger/Photolibrary/Getty Images Plus
Koalas typically breed from August to February. Male koalas attract the females through their loud vocal bellows. Females usually have one baby koala per year, producing some six or so offspring over the course of their lifetime, since females don't always breed each year.
After becoming impregnated, a koala will give birth after a gestation period of a little longer than a month (about 35 days). The baby is called a "joey" and is usually very small. The baby may weigh under .0025 pounds and be under an inch long, about the size of an almond. The joey is blind at birth and doesn't have any hair. It travels from the birth canal to its mother's pouch, where it will remain for approximately the first six to seven months of its life. Even after developing to the point that it is no longer in its mother's pouch, the joey will often remain with its mother until its next brother or sister appears outside the mother's pouch the following year.
Koalas are mainly threatened by habitat loss. Human encroachment on their habitat from land clearing has a large impact on their survival. They can also be impacted by bush-fires and disease. Koalas are susceptible to the bacteria that cause chlamydia. This disease can lead to the development of conjunctivitis, an eye infection that may result in blindness. Chlamydia may also result in pneumonia and infections of the urinary tract and reproductive systems. Incidences of complications from chlamydia increase in koala populations that experience high environmental stress.
Koalas are designated as vulnerable by the International Union for Conservation of Nature (IUCN). According to the IUCN, approximately 100,000 to 500,000 animals are left in the wild. While koalas themselves have some protection under the law, their population continues to decrease mainly due to loss of habitat. The Koala Protection Act is proposed legislation in Australia to help protect the koala's habitat. The Australian Koala Foundation believes that there are less than 100,000 left in the wild, and even as few as 43,000.
There is one species of koala, but scientists disagree whether or not there are sub-species. The most common three sub-species of koalas are considered to be: Phascolarctos cinereus adustus (Northern/Queensland), Phascolarctos cinereus cinereus (New South Wales) and Phascolarctos cinereus victor (Victorian). These sub-species are classified based on slightly different physical characteristics like physical size and fur properties. Based on these characteristics, some scientists believe that there are three sub-species, others two, and others none.
Koalas and HumansThis girl is feeding a koala. Peter Phipp/Photographer's Choice/Getty Images Plus
Humans and koalas have a long and varied history. Beginning in the early 1900s over a million were killed for their fur. The population of koalas was in danger of being wiped out before the practice stopped. Koalas can be very aggressive when disturbed or surprised by humans in their natural habitats. They defend themselves with their sharp teeth and pointed claws which are similar to talons. These structures are capable of shredding skin and can inflict considerable damage.
- "Koala." National Geographic, 21 Sept. 2018, www.nationalgeographic.com/animals/mammals/k/koala/.
- "Koala." San Diego Zoo Global Animals and Plants, animals.sandiegozoo.org/animals/koala.
- "Physical Characteristics of the Koala." Australian Koala Foundation, www.savethekoala.com/about-koalas/physical-characteristics-koala.
- "The Life of a Koala ." Australian Koala Foundation, www.savethekoala.com/about-koalas/life-koala.