Koalas are distinctive marsupials native to Australia, immediately recognizable by their stout, tailless bodies and large heads. They are often found in coastal regions of eastern and southern Australia, including Queensland, New South Wales, Victoria, and South Australia. These animals are known for their specialized diet and arboreal lifestyle.
Distinct Physical Features
Koalas possess a dense, woolly fur that ranges in color from silver-grey to chocolate brown, providing insulation against environmental changes. The fur is denser on their back, while their chest, inner arms, ears, and underside display white fur. Their large, round ears are covered in soft, silvery fur, and they have a broad, flat, leathery black nose that is furless.
Their strong limbs and sharp, curved claws are well-suited for gripping tree trunks and branches. The forepaws have two opposable “thumbs” (the first and second digits) that allow for a secure grip. On their hind paws, the second and third digits are fused, forming a comb-like structure used for grooming their fur.
Koalas measure between 60 to 85 cm (24 to 33 inches) in body length. Their weight varies significantly by region; southern koalas in Victoria can weigh up to 14 kg (31 pounds), about twice as much as their northern counterparts in Queensland. Males are about 50% larger than females and possess a broader face and a more prominent scent gland on their chest.
Specialized Adaptations for Eucalyptus
Koalas have developed adaptations to subsist almost exclusively on a diet of eucalyptus leaves, which are fibrous, low in nutrients, and contain toxic compounds to most other animals. Their digestive system is adapted to detoxify these compounds. A long caecum, an intestinal pouch up to 2 meters (7 feet) long, plays a significant role in this process.
The caecum houses millions of bacteria that break down the tough fiber in eucalyptus leaves into more absorbable substances. Despite this specialized digestion, koalas absorb only about 25% of the fiber they consume. This low nutritional yield necessitates a very slow metabolic rate, allowing food to remain in their digestive system for an extended period to maximize nutrient extraction. Koalas also possess strong molars for grinding tough plant material and sharp front teeth to nip leaves from branches. They obtain most of their water intake directly from the moisture within eucalyptus leaves, reducing their need to drink free water.
Daily Life and Social Behavior
Koalas are arboreal, spending most of their lives in eucalyptus trees for food, shelter, and social interaction. Their climbing abilities allow them to navigate their arboreal environment. Due to their low-energy, nutrient-poor diet, koalas conserve energy by sleeping extensively, resting between 18 to 22 hours per day.
Koalas are primarily nocturnal or crepuscular, active during the night or at dusk and dawn. While considered solitary animals, their home ranges often overlap, particularly in shared trees where social interactions occur. They communicate through various vocalizations; males use deep grunting bellows to assert dominance and indicate their location. Females also use calls to express aggression or as part of sexual behavior, while mothers and joeys make softer clicking, squeaking, or humming sounds.
Newborn koalas, called joeys, are underdeveloped at birth, resembling a jelly bean in size. They crawl into their mother’s backward-facing pouch, where they remain for about six months, nursing and completing their early development. After emerging from the pouch, joeys ride on their mother’s back for an additional two to four months until they are one year old and ready for independence.