Koala Bears Hug Trees To Stay Cool

The mere mention of the Koala bear immediately conjures up the image of an adorable creature hugging a tree whilst cocking its head to one side.

According to a new study, scientists have worked out why the Australian marsupial is such an avowed tree hugger. Simply put the tree trunks help keep the koala bear cool.

Study co-author Michael Kearney, who is an ecologist at Australia’s University of Melbourne says hugging trees is a useful way of getting rid of excess heat during a hot day.

Tree huggers

Nobody has previously asked the question of why koalas hug trees given they spend so much time up in them, where they sleep and munch on leaves. In the past people used to believe they were simply taking a break in a more stable spot after eating a meal in the branches Dr. Kearney said.

As a result the discovery came as a surprise to Dr. Kearney and his doctoral candidate student Natalie Briscoe who were actually trying to work out how koalas on French Island very near Melbourne would respond as the Australian continent heats up as a result of climate change. For most of the year they region is cool however during the summer the temperature can regularly spike above 40 degrees Celsius.

Ms. Briscoe measured both shade and wind levels but was unable to find any particular trends. She then pointed an infrared thermometer at the tree trunks the koalas were hugging and found they were considerably cooler than the ambient temperature of the air, sometimes by as much as 5 degrees Celsius.

Ms. Briscoe also found that koalas clung to acacia trees despite the fact their normal diet is eucalyptus leaves.

“As it got hotter the koalas went farther down the trees and started to really hug onto the tree trunks. That seemed strange to us until we figured out that the trees are a bit cooler.” Dr. Kearney said

Stay cool

Like dogs, and a few other mammals, koala bears pant in order to stay cool, this lets evaporated moisture in their mouths carry heat away from their bodies.

When the team analysed koala bear heat transfer they found that the bears save half of the water that would be used for panting by hugging trees instead.

Most of the water koalas have comes from their diet, but because the eucalyptus leaf is spiked with a toxin the bears are only able to eat a limited amount before suffering harm from the toxin Dr. Kearney said.

This means hugging trees is critical to the survival of a koala bear on a hot day, enabling them to cool down without wasting water through panting.