Although they are commonly referred to as
"koala bears" because of the resemblance to
teddy bears, koalas are not bears. The koalas are
marsupials. This is one of the oldest classes of animals,
existing since over fifty thousand years ago.
Koalas average about twenty-six pounds in weight
and thirty-one inches in length. The coat of the koala
is the thickest among the marsupials and has a
gray to tawny color. White coloration appears on
the chin, chest, and forelimbs. The fur is short,
soft, densely packed, and springy to the touch. It is
the most effective fur insulation among animals.
The koalas do not rely on fat beneath the skin for
insulation; rather, blood flow to the extremities
can be reduced as a means to conserve heat. In the
rain, water runs off the koala's fur. Only sick koalas
will appear to be wet when it rains.
Koalas are nocturnal and highly arboreal, living solitary lives high up in eucalyptus trees. Koalas are known as phalangers, because they use their hands and hind feet to effectively grip tree trunks and branches when tree climbing and jumping from tree to tree. They walk with a clumsy gait in the following sequence: front right foot then back left foot, front left foot, back right foot. They have a very specialized diet, feeding almost exclusively on the leaves of a few species of eucalyptus. The leaves provide most of their water intake; in fact, the word "koala" means "no drink" in Aboriginal languages. For an average day, a koala will consume about a pound of leaves. They are very fussy eaters, typically being very careful in selecting which leaves from a bough to ingest. The koala uses a set of thirty teeth, comprising incisors, canines, premolars, and molars, to chew the eucalyptus leaves. Each day the koala spends approximately eighteen to twenty-one hours sleeping or resting. In order to communicate, the koala uses a range of vocalizations. The male koala uses a deep, grunting bellow to communicate its physical and social position. The sound can resemble a far-off rumbling, like a motorcycle or pig snorting. During the mating season, the koala will use the bellowing as a means to locate and accurately pinpoint potential mates. The mating call is a deep, loud, guttural sound that can be heard for long distances. Female koalas do not show the same level of bellowing. Their calls communicate aggression and are part of the mating ritual. Both the male and female koalas share a similar call, sounding like a baby screaming. This is often accompanied by shaking and signals fear. Mother and cubs make soft squeaking noises to one another, as well as humming or murmuring.
Females of the species have a pouch in which the young develop. The young are born in nearly embryonic form about the size of a human's little finger. After birth, the infant travels to the mother's pouch, where it attaches to teat. The teat then becomes engorged and forms a seal with the newborn. A single offspring is usually born. It is not until twenty-four weeks after birth that the young is covered with fur and develops teeth. The first six months of life are spent in the mother's pouch. The cub remains with the mother until about twelve months after birth. Mating is a brief event that takes place about once a year. Male koalas are nomadic and play virtually no part in the raising of the young. Extensive chlamydia infection has caused widespread infertility in female koalas and is a major contributing factor in their declining numbers.
Genus and species: Phascolarctos cinereus
Subspecies: P. c. victor (Victoria), P. c. cinereus (New South Wales), P. c. adustus (Queensland)
Geographical location: Two main groups living out in the wild are in eastern Australia in an area extending from Cooktown in northern Queensland to southwestern Victoria; have been introduced into western and southern Australia
Habitat:Wild eucalyptus forests and woodlands; they are found only in pockets with suitable vegetation of a relatively small number of eucalyptus species that they prefer to ingest
Gestational period: Thirty-five days
Life span: Thirteen to eighteen years
Special anatomy: Females have a pouch that faces the rear and has a drawstring type muscle which can be tightened to close the opening; mammary glands are located along the abdomen within the pouch; females have a duplicate reproductive system with two vaginas; males have dual-pronged, forked penises; each hand has two opposable thumbs, which are crucial for the ability to climb and cling to trees; digestive system includes a caecum, a structure used to digest eucalyptus leaves and assist in water extraction
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