Koala is a charming marsupial with thick-set body, small eyes and large ears. The wool-like coat of the animal is thick but soft, colored with ash-grey. The densely packed fur on the bottom serves as a cushion, allowing koalas to sit upon rough tree branches. The under parts as well as the tips of hairs on their ears are white. In the center of their chest, adult male koalas have the identifying brown colored "scent gland". One of the key characteristics of this animal is a very strong sense of smell, which helps them distinguish between poisonous and eatable leaves. They have large sharp claws on their long limbs, which help them in climbing trees, as well as 5 digits, including opposable thumbs, allowing them to grip tree branches and food.
The ideal habitat of Koala is eucalyptus forests, humid woodlands and riparian areas. The species is distributed across eastern and southeastern Australia, including northeastern, central and southeastern Queensland, eastern New South Wales, Victoria as well as southeastern parts of South Australia.
Koalas are asocial animals, congregating only during the breeding season. They usually form large, loosely organized groups in areas with abundant suitable trees, with a single individual per tree. During the rest of the year, koalas tend to live solitarily, showing very little social behavior. They are arboreal animals, dwelling in trees. Koalas are exceptionally good climbers. Meanwhile, when on the ground, they are very slow walkers. During the daytime hours, these nocturnal animals usually sleep in the fork of eucalyptus trees. Normally, koalas are quiet animals. However, when threatened or alarmed, they typically give out a call, reminding cry of a human baby, and accompanying it by shaking. In addition, during the breeding season, males of this species begin to emit bellowing calls. Koalas also scent-mark their trees, which is a form of communication.
They are herbivorous animals, feeding primarily upon leaves of eucalyptus tree. Meanwhile, they consume leaves of 30 various species of eucalyptus tree. In addition, they supplement their usual diet with melaleuca, foliage from leptospermum and acacias.
These animals have polygynous mating system with the dominant male, mating with most of females. Koalas mate from December to March. Gestation period in koalas lasts for only 35 days, yielding a single baby. During the first 5 - 6 months of its life, the joey lives in the pouch of its mother, feeding exclusively on milk. By the age of 6 months, the young is weaned. The young then starts feeding upon pap - partially digested vegetation, found in excrement of its mother. At 7 months old, the baby comes out of the pouch of its mother, beginning to cling to her back. Then, at about 1 year old, young koala becomes independent, after which the youngster typically stays with its mother for another few months before it leaves. Male koalas reach sexual maturity by 3 - 4 years old while females are mature at 2 - 3 years old.
The primary threat to koala population in Australia is destruction, fragmentation and alteration of their natural range, due to which the animals are often hunted by dogs as well as collided with vehicles. Other notable threats include diseases and bushfires. The animals are also exposed to drought, which leads to considerable number of mortality in certain populations of koala.
The estimated koala population in the wild is about 300,000 mature individuals across Australia. On the IUCN Red List, koala is classified as Vulnerable (VU) with a decreasing population trend.