Koala
Phascolarctos cinereus
The koala has enjoyed considerable conservation success. However, although it is no longer threatened with extinction, managing the remaining populations is proving problematic for conservationists. Koalas manage to survive on a diet that no other mammal will touch-eucalyptus leaves. Tough, dry, and with a very low nutritional value, the leaves also contain indigestible materials and compounds that are highly poisonous to most other animals. Koalas are able to exist on this poor diet by having efficient digestive systems that will not only break down the toxins but also extract every available calorie. They also conserve energy by spending up to 20 hours a day resting. Until the arrival of European settlers in Australia in the late 18th century the ability of the koala to eke out a living from a food that no other animal could eat meant that it was a highly successful animal, well adapted to its diet and environment.
Consequences of Colonization
European settlement brought a number of threats to Australia’s native wildlife. It destroyed the natural habitat and caused a marked increase in forest fires. The koala was also hunted for its fur. By the early 20th century koalas were facing a very real threat of extinction. Disaster was narrowly averted when the koala was made a nationally protected species in 1927. The koala has now returned to much of its original range; but because its habitat is patchy, it will never be as common as it once was. Although the koala as a species is out of immediate danger, individuals and localized populations are still threatened. Many koalas are killed on the roads or attacked by dogs, and forest fires can wipe out whole colonies at a time.
Victims of Success
The biggest problem is the patchy, isolated nature of the remaining koala habitat. The species responds so well to conservation that protected populations often increase to the point where the animals begin to damage the trees that they rely on for survival. Yet surplus animals cannot easily disperse if their forest home is surrounded by urban development or vast areas of open pastureland, as is now the case in much of eastern Australia. In overcrowded conditions the koala is especially vulnerable to a disease caused by the Chlamydia psittaci bacterium. Conservation programs therefore face the difficult task of establishing healthy koala populations without creating overpopulated, disease-ridden colonies in which surplus animals have to be culled. The least damaging solution is to move the excess koalas to other areas of suitable habitat. However, after 200 years of logging, development, and clearance for agriculture there are very few large areas of eucalyptus forest available. Consequently, koalas are often moved to other isolated patches of woodland where they soon become overcrowded again. The only real solution is to create “corridors” of habitat linking the isolated patches so that koala populations can spread themselves more evenly. Tracts of suitable land connecting isolated koala populations would benefit the species in other ways: When koala colonies are decimated by natural events such as forest fires or outbreaks of Chlamydia, koalas dispersing from other areas would be able to recolonize the affected sites.
Statistics Koala
Phascolarctos cinereus
- Family: Phascolarctidae
- World population: About 40,000, but estimates vary widely and are controversial
- Distribution: Eastern Australia
- Habitat: Eucalyptus forests below 2,000 ft (600 m)
- Size: Length head/body: 28-31 in (72-78 cm); animals from south of range larger than those in north. Weight: 11-24 lb (5-11 kg); males can be half as heavy again as females
- Form: Stout, bearlike animal with thick, woolly, grayish-brown fur on back, fading to white on belly. Head large with rounded furry ears, beady black eyes, and large black nose. Legs short with 5 large claws on each foot.
- Tail short and stumpy. Female has pouch that opens to the rear
- Diet: Leaves of various species of eucalyptus
- Breeding: Single young (occasionally twins) born in midsummer after gestation of 25-30 days; young spend 5-7 months in pouch, weaned at 6-12 months; mature at 2 years. Life span up to 20 years
- Related endangered species: No close relatives, but the northern hairy-nosed wombat (Lasiorhinus krefftii) of northeastern Australia is listed as CR
Koalas, like other Australian marsupials, are born very early and suckled by their mother-often in a pouch-for the first months of life. Koala young are weaned on to `pap,” a special form of the mother’s droppings that provides the baby with the gut bacteria it needs to digest eucalyptus leaves.
