A species
Koala
Phascolarctos cinereus
The sleepy gum-leaf specialist
You and the koala last shared an ancestor about 160 million years ago (on 18 December, if life's history were one year).
Imagine living on leaves that would poison many other animals. That is everyday life for the koala. It feeds almost entirely on eucalyptus leaves, which are low in energy and contain oils and other chemicals that can poison other animals. Because the leaves give little energy, it spends about 20 hours a day resting and dozing, often wedged in a branch fork, and feeds for only a few hours.
Although it looks like a small bear, it is a marsupial that raises tiny young. Its closest living relatives are wombats, and it is a more distant relative of the red kangaroo shown beside it on the tree. With its thick ash-grey coat and pale belly, big fluffy ears and large black nose, plus strong arms and gripping claws, it is built to climb and sit wedged high in gum trees.
Wild koalas live in eucalypt forests and woodlands in eastern Australia, from northern Queensland to south-eastern South Australia, sometimes even where food trees remain on farms and in suburbs.
Tiny baby, special first food
A newborn baby is only about 2 cm long, about as long as a jellybean, and is born blind and hairless. At about five to six months old it eats a special soft food called pap, a kind of droppings, that gives it helpful gut bacteria for digesting leaves. After about six months in its mother's rear-opening pouch it rides on her back or belly.
Fussy eater with a very long gut
Koalas eat only about 70 of nearly 900 kinds of gum trees, and favourites change with place and season. An extra-long gut part called the caecum, up to about 2.5 metres long and longer than a tall grown-up, helps break down the tough, fibrous leaves.
Loud calls and a risky neighbourhood
Males make loud bellowing calls and rub scent on trees to attract mates and warn rivals. Koalas live about 10 to 18 years. Cars and dogs are among the most common direct causes of death, more than natural hunters such as dingoes and large owls.