Koalas feed almost exclusively on eucalyptus leaves, so their habitat is invariably eucalypt forest and woodland. However, they can tolerate a surprisingly diverse range of envi-

Koala {Phascolarctos cinereus). {Illustration by Michelle Meneghini)

MLM ©2003

Koala {Phascolarctos cinereus). {Illustration by Michelle Meneghini)

A Queensland koala (Phascolarctos cinereus adustus) sleeps in a tree. (Photo by John Shaw. Bruce Coleman, Inc. Reproduced by permission.)

ronmental and climatic conditions. In the tropical north habitat is often dense thicket, with high year-round temperatures and strong seasonal rainfall. Rainfall is also high in the temperate mountain rainforests of the south, but winters can be much colder. This fertile habitat can support populations as high as three animals per acre (0.4 ha), a stark contrast to the semi-arid open woodland habitat of the west, where a single animal may require 250 acres (100 hectares) to survive.

In temperatures above 77°F (25°C) koalas use evaporative cooling in their airways to regulate temperature, by breathing rapidly, but reduce water loss by decreasing the amount of water in their urine. In cold temperatures koalas, like humans, conserve heat by reducing blood flow to extremities, and have also been seen to shiver, a means of producing heat by rapid muscle contraction.

ductivity of the environment, but can be as little as 2.5 acres (1 ha) for a male in a fertile habitat, and half that for a female. Within this range an animal may live much of its life in only a dozen favored trees. A dominant adult male's range will overlap the range of up to nine females and a number of subordinate and subadult males.

Within the area of a stable social group individual koalas will "own" a number of food trees and "home range trees" marking the edge of their range. A koala trespassing into an "owned" tree may be aggressively attacked by the resident, but scent markings and scratchings usually warn animals that a tree is under possession. Other trees where ranges overlap will be shared, and it is here that limited social interaction takes place.

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