Koala

The koala (Phascolarctos cinereus) is perhaps one of the most popular of the marsupials other than the kangaroo.  It is endemic to Australia.  It is rated as 'Near Threatened' by the IUCN and was previously hunted in large numbers for its fur.

Physical Features
The koala is a small marsupial that measures about 2 to 3 feet in length.  They have a very small tail that measures about 2 cm.  Males are larger than females.  Their weight ranges from 5 kg to 15 kg.  The koala is stockily built with teddy bear like features with woolly grayish brown fur and fluffy ears.  The fur on the ventral side is paler.  Koalas have one of the most insulating fur (dorsal side) of any marsupial while the ventral fur reflects solar radiation.  Males have more curved noses than females.  Koalas have short, powerful limbs with sharp claws that enable it to climb and cling on to eucalyptus trees on which it spends most of its life.  Koalas in the southern regions are found to be 50% larger than those in the north.  Koalas have the smallest brain in proportion to body weight of any animal.

A koala feeding.

Diet
Koalas are herbivorous.  The main constituent of their diet is eucalyptus leaves.  They may be found eating leaves from Acacia and Leptospermum.  They eat for about 4 hours in the night eating and may eat about 500 grams of leaves.  They eat leaves from about 30 species of eucalyptus trees out of the 600 species present.  They show more preference toward eucalyptus leaves with higher protein and lignin (polymer that is present in cell walls of plant cells).  They may descend to the ground for eating soil and gravel that helps in digestion.  The droppings of the mother is one of the first solid food eaten by young koalas as it carries disease fighting microbes.

Distribution and Habitat
Koalas are found in eastern Australia and inhabit eucalyptus forests.  They spend most of their time on eucalyptus trees.

Breeding

A koala sleeping

After a gestation period of 25 to 35 days, a single young is born during summer.  Twins are occasionally born.  They are suckled for 6 months in the mother's pouch.  After that period, they cling onto the mother's back.  

Behavior
Koalas are considered as one of the most laziest animals.  They are nocturnal and spend 4 hours in the night for feeding.  For the remaining 20 hours, they sleep.  They are arboreal and occasionally come to the ground either for eating soil or for crossing open spaces.  They normally lead a solitary life.

Conservation Status
The koalas are rated as 'Near Threatened' by the IUCN.  Koalas have few natural predators other than large birds of prey.  Sometimes, while crossing land, feral dogs attack and kill it.  A bacteria known as Chlamydia has caused a disease that affects koalas.  In the early 20th century, koalas were extensively killed for their fur.  Koalas are also affected by habitat destruction.  Now their numbers are slowly increasing due to the efforts of conservationists.