Koala - biology.

« V REPRODUCTION Female koalas become sexually mature around 18 to 24 months of age.

They can produce one offspring a year until they reach about 13 years of age.

Males begin toproduce sperm around age 2 and, in the absence of older, stronger males, they may breed at that young age.

More often, however, a male must grow big enough tocompete with other males for females, and mating generally begins for males at about 4 years of age. The breeding season for koalas is from October to May, during the spring and summer months in Australia.

This seasonal breeding allows young to emerge from themother’s pouch when food is abundant.

Mating occurs during estrus, the brief stage in the female’s reproductive cycle when eggs are released and she is receptive tomating. Koalas partake in courtship behaviors that look a lot like fighting.

With much bellowing, a male attacks and tries to mate with every female in the area.

The male seemsunable to tell the difference between a female that is in estrus and one that is not, an unusual disability for a mammal.

If a female is not in estrus, she will drive themale away by biting and scratching to escape his advances, while screaming loudly.

If a female is in estrus mating occurs, usually at night.

Males and females do notstay together after mating and males play no role in raising young. After mating, gestation (the time between conception and birth) lasts about 35 days.

Usually only one young is born; twins are rare.

The newborn joey is about the sizeof a small grape and weighs less than 6 g (0.2 oz).

At birth the joey is hairless, its eyes are closed, and it has no ears.

Its hind limbs are just buds, but its shouldersand front legs are more developed, with tiny claws.

The newborn uses these front legs to crawl from the birth canal through its mother’s belly fur to her pouch opening.Once in the warm pouch, the joey attaches its lips to one of the mother’s two nipples. The joey will stay in the pouch for about seven months, growing rapidly.

After about three months, the joey weighs nearly 57 g (2 oz), its eyes have opened, its earshave developed, and fur begins to appear.

At about six months, the joey has full body fur and begins to poke its head outside the pouch.

After seven months the joeyno longer fits in the pouch and rides around on its mother’s back. A joey drinks only its mother’s milk until around six months of life, when it begins to eat leaves that have been digested and eliminated by its mother.

These mushyyellowish-green leaves, called pap, help the joey acquire the intestinal microbes necessary for the digestion of eucalyptus leaves.

The joey eventually begins to eat rawleaves, foraging from its mother’s back. Joeys become fully weaned around 12 months.

At this time, the mother is usually pregnant again and stops feeding the joey.

The joey may stay near the mother foranother 6 to 12 months.

By age 2, females are sexually mature and they may settle near their mothers, but males are often driven away by other adult males andmust find a new territory. VI BEHAVIOR Koalas spend much of their time in a tree, resting in order to conserve energy to compensate for their nutrient-poor, low-energy diet.

They sleep about 20 hours a day,sit and munch food for 1 to 3 hours a day, and spend only about four minutes a day actively moving between branches or trees, grooming, and partaking in socialactivities.

Most feeding occurs from about 5 PM to midnight.

Koalas feed in several “bouts,” each lasting an average of 20 minutes. Koalas sleep in the same trees that they feed in, resting in the forks of trees and occasionally stretching along a branch.

They change trees once a day or less, typicallyclimbing down a tree feet first and walking awkwardly on the ground to another tree.

At a new tree koalas spring from the ground to catch their claws in the bark andthey then use their muscular limbs to scramble up the trunk.

In trees, large pythons are the koala’s primary predators, and owls and eagles sometimes snatch youngkoalas off their mothers’ back.

While on the ground the koala is vulnerable to predators such as dingoes and domestic dogs.

Some koalas are hit by motor vehicleswhen they cross a road to get to another tree. Except for the mother and her young, koalas live alone.

Each koala maintains a home range consisting of a number of trees.

Within its home range, a koala uses only asmall number of trees, with up to a third of its time spent in one favorite tree.

Home ranges vary in size depending on the nature of the habitat, and male home rangesare larger in size than those of females.

In areas of good habitat—marked by fertile soil, warmer temperatures, plentiful rainfall, and the preferred eucalyptusspecies—home ranges average 1 to 2 hectares (3 to 4 acres); in moderately good habitat home ranges average 2 to 3 hectares (5 to 8 acres); and in very poor habitata male home range may reach nearly 200 hectares (500 acres). The home range of a koala may overlap with the home ranges of other koalas.

When there are many individuals in one area, adults will share a single tree, but onlybriefly.

It is in the shared trees that most social interaction occurs among koalas.

Koalas communicate with vocalizations, including loud, low bellows emitted by adultmales.

Males bellow year-round, but most often during the breeding season when males fight with other males to gain dominance.

Occasionally a koala may move along distance, especially a young animal leaving its mother to strike out on its own.

One study reported a male koala moving more than 8 km (5 mi) during a six-weekperiod. VII STATUS OF KOALAS Koalas are not classified as an endangered species under Australia's Endangered Species Protection Act.

They are categorized as “lower risk/near threatened,” in theRed List of Threatened Species compiled by the World Conservation Union (IUCN), a nongovernmental organization that compiles global information on endangeredspecies.

While these classifications indicate a relatively low level of concern, the number of koalas in Australia and their endangered status is a matter of debate amonggovernment officials and conservationists.

Wildlife management experts in the Australian federal and state governments believe koalas are abundant and in little dangerof extinction nationally, although these authorities do believe that some local populations may be threatened.

Other scientists and conservationists hotly dispute thisview because they believe that the koala is in danger of extinction, primarily threatened by habitat loss. Over the last 200 years more than 80 percent of eucalyptus forests have been cleared to make room for farming, housing, and other human development.

Forest fireshave also destroyed koala habitat.

As more and more eucalyptus forests have been decimated, koala populations have become fragmented, surviving in the fewremaining patches of forests. Unable to travel to other forests, koalas have a limited choice of breeding partners, increasing the chance for inbreeding (mating between closely related animals).Biologists are concerned that the genetic diversity of koala populations will steadily decline as a result of inbreeding.

This growing genetic uniformity can have seriousconsequences.

Because inbred animals share so many genes, they are likely to be equally vulnerable to disease and other threats.

If a potentially lethal disease strikesa koala population with a similar genetic makeup, the entire group may die. Fragmented populations can also lead to overpopulation of a limited habitat.

When a koala population grows too large for a patch of forest, the animals over browseleaves and destroy the very trees that sustain the koala population, resulting in starvation.. »