Koalas

Koala Facts

Classification:

• Kingdom: Animal
• Phylum: Vertibrata
• Class:Mammalia
• Subclass: Marsupialia
• Order: Diprotodontia
• Suborder: Vombatiformes
• Infraorder: Phascolarctomorphia
• Family: Phascolarctidae
• Genus and species:Phascolarctos cinereus
• Subspecies: (disputed)P. c. victor (Victoria),P. c. cinereus (New South Wales),P. c. adustus (Queensland)
• Geographical location: Two main groups living in the wild are in eastern Australia in an area extending from Cooktown in northern Queensland to southwestern Victoria; have been introduced into western and southern Australia
• Habitat: Wild eucalyptus forests and woodlands; they are found only in pockets with suitable vegetation of a relatively small number of eucalyptus species that they prefer to ingest
• Gestational period: Thirty-five days
• Life span: Thirteen to eighteen years
• Special anatomy: Females have a pouch that faces the rear and has a drawstring-type (sphincter) muscle which can be tightened to close the opening; mammary glands are located along the abdomen within the pouch; females have a duplicate reproductive system with two vaginas; males have dual-pronged, forked penises; each hand has two opposable thumbs, which are crucial for the ability to climb and cling to trees; digestive system includes a caecum, a structure used to digest eucalyptus leaves and assist in water extraction

Although they are commonly referred to as "koala bears" because of the resemblance to teddy bears, koalas are not bears. The koalas are marsupials. This is one of the oldest classes of animals, existing since over fifty thousand years ago, and differ significantly from placental mammals when it comes to bearing young. Koalas average about twenty-six pounds in weight and thirty-one inches in length. The coat of the koala is the thickest among the marsupials and has a gray to tawny color. White coloration appears on the chin, chest, and forelimbs. The fur is short, soft, densely packed, and springy to the touch. It is the most effective fur insulation among animals. The koalas do not rely on fat beneath the skin for insulation; rather, blood flow to the extremities can be reduced as a means to conserve heat. In the rain, water runs off the koala’s fur. Only sick koalas will appear to be wet when it rains.

Koala Life

Koalas are nocturnal and highly arboreal, living solitary lives high up in eucalyptus trees. Koalas are known as phalangers because they use their hands and hind feet to effectively grip tree trunks and branches when tree climbing and jumping from tree to tree. They walk with a clumsy gait in the following sequence: front right foot then back left foot, front left foot, back right foot. They have a very specialized diet, feeding almost exclusively on the leaves of a few species of eucalyptus. The leaves provide most of their water intake; in fact, the word "koala" means "no drink" in Aboriginal languages. For an average day, a koala will consume about two and a half pounds of leaves. They are very fussy eaters, typically being very careful in selecting which leaves from a bough to ingest. The koala uses a set of thirty teeth, comprising incisors, canines, premolars, and molars, to chew the tough eucalyptus leaves. Its specialized gut allows bacteria in the digestive system to neutralize the toxins of the eucalyptus leaves that make them inedible to most other species. Because the leaves are not particularly nutritious, each day the koala spends approximately eighteen to twenty-one hours sleeping or resting to conserve energy.

In order to communicate, the koala uses a range of vocalizations. The male koala uses a deep, grunting bellow to communicate its physical and social position. The sound can resemble a far-off rumbling, like a motorcycle or pig snorting. During the mating season, the koala will use the bellowing as a means to locate and accurately pinpoint potential mates. The mating call is a deep, loud, guttural sound that can be heard for long distances. Female koalas do not show the same level of bellowing. Their calls communicate aggression and are part of the mating ritual. Both the male and female koalas share a similar call, sounding like a baby screaming. This is often accompanied by shaking and signals fear. Mother and cubs make soft squeaking noises to one another, as well as humming or murmuring.

Koala Reproduction and Conservation

Females of the species have a pouch in which the young develop. The young are born in nearly embryonic form about the size of a human’s little finger. After birth, the infant travels to the mother’s pouch, where it attaches to a teat. The teat then becomes engorged and forms a seal with the newborn. A single offspring is usually born. It is not until twenty-four weeks after birth that the young is covered with fur and develops teeth. The first six months of life are spent in the mother’s pouch. The cub remains with the mother until about twelve months after birth. Mating is a brief event that takes place about once a year. Male koalas are nomadic and play virtually no part in the raising of the young. Extensive chlamydia infection has caused widespread infertility in female koalas and is thought by some to be a major contributing factor in their declining numbers, though others suggest the infection serves as a natural population control and is only problematic when populations are stressed by other factors.

The loss of eucalyptus forest habitat throughout Australia is another major threat to koala populations. The animals were formerly hunted, but the implementation of government protection and conservation programs allowed their numbers to stabilize. However, other pressures, including climate change, have contributed to a decline. In 2016 the International Union for Conservation of Nature and Natural Resources (IUCN) changed the koala's Classification from "least concern" to "vulnerable" on its Red List of Threatened Species, though a lack of detailed population data led other groups to challenge that assertion.

In June 2019, several severe bushfires broke out in southeast Australia, lasting into early 2020. By the end of January 2020, more than 27.2 million acres had been destroyed, including about 30 percent of the koala’s Australian habitat. The event led to the death of about 30 percent of the koala population in the area. In 2022, the Australian government officially listed the koala as endangered due to its continued decreasing population.

Principal Terms

arboreal: living in trees

bellowing: guttural sound used in communication

caecum: structure in the digestive tract that aids in digestion and water retention

marsupial: animals whose young develop in a pouch

nocturnal: active at night

Bibliography

"Australia Fires: A Visual Guide to the Bushfire Crisis." BBC, 31 Jan. 2020, www.bbc.com/news/world-australia-50951043. Accessed 12 Feb. 2020.

Australian Koala Foundation, www.savethekoala.com. Accessed 5 July 2024.

Hunter, S. Koala Handbook. Chatto & Windus, 1987.

"Koala." National Geographic, www.nationalgeographic.com/animals/mammals/facts/koala. Accessed 5 July 2024.

"Koalas." International Fund for Animal Welfare, www.ifaw.org/animals/koalas. Accessed 5 July 2024.

Lee, A., and R. Martin. The Koala: A Natural History. New South Wales University Press, 1988.

Phillips, K. Koalas: Australia’s Ancient Ones. Macmillan, 1994.

Sharp, A. The Koala Book. Pelican, 1995.

Zhou, Naaman. "Australia's Environment Minister Says Up to 30% of Koalas Killed in NSW Mid-North Coast Fires." The Guardian, 26 Dec. 2020, www.theguardian.com/australia-news/2019/dec/27/australias-environment-minister-says-up-to-30-of-koalas-killed-in-nsw-mid-north-coast-fires. Accessed 12 Feb. 2020.