Science News

Why koalas took to eucalyptus

Koalas, those dozy, lovable emblems of Australia, look like teddy bears but being marsupials are only very distantly related to real bears. A new study sheds light on the little-known evolution of koalas, revealing that the their ancestors didn’t have the specialised teeth and jaws that would have allowed them to eat tough and somewhat toxic eucalyptus leaves.

It turns out that koalas only more recently adapted to cope with this unique diet. Publishing in the Journal of Vertebrate Palaeontology, researchers from the University of New South Wales and the CSIRO in Australia investigated the fossilised skulls of two koala species that lived in the Australia in the Miocene, around 24 – 5 million years ago.

The team also found some striking similarities in the prehistoric and modern koalas. Both have a round hollow bony structure in the ear, which is a key to their ability to create loud and complex vocalizations. Koalas may be lazy but they can be extremely noisy, bellowing at each other across the treetops, something it turns out they have been doing for a long time and long before developing their eucalyptus leaf habit. Eucalypts only became abundant as Australia drifted away from the tropics, becoming drier with less rainforests.

Sadly, this week also saw news that koalas are among the group of species that are likely to be hit hardest by climate change. Scientists from the International Union for the Conservation of Nature (IUCN) highlighted the plight of a long list of species that will not fair well in the coming years, including clown fish, beluga whales and emperor penguins. Koalas may face starvation as the nutritional quality of eucalyptus leaves are predicted to decline as levels of carbon dioxide increase.

21st Dec 2009