Koalas are treehuggers because it’s cool

Koalas make coo-worthy photos when they cuddle up to Australia’s trees, where they live. But trees are more than shelter to the arboreal marsupials. Scientists recently learned that koalas use trees as their personal air conditioners.

The bears are vulnerable to dehydration and Australia’s hot climate, said Andrew Krockenberger, a researcher at James Cook University. A quarter of the koalas in one New South Wales population perished during the 2009 heatwave, he said. Koalas can pant like a dog or lick themselves to keep cool, but that can dehydrate the animals quickly, said Natalie Briscoe from the University of Melbourne.

Trees not only provide shade, but keep a cooler temperature, even during extreme heat. Krockenberger, Briscoe and their team observed 30 koalas on French Island in southeast Australia during a heatwave. Using thermal imaging cameras, they watched the bears choose trees in the heat.

The images showed that the animals chose to hug trees that were cooler than the air by as much as 9 degrees. Hugging the branches helped the koalas cool off.

“Access to these trees can save about half the water a koala would need to keep cool on a hot day,” Briscoe said.

Co-author Michael Kearney said the findings were important as climate change is bringing about more extreme heat, something already evident in Australia. Maintaining a healthy tree population will help koalas and other animals survive, he said.

“Cool tree trunks are likely to be an important microhabitat during hot weather for other tree dwelling species including primates, leopards, birds and invertebrates. The availability of cooler trees should be considered when assessing habitat suitability under current and future climate scenarios,” he said.

Their findings were published this week in the journal Biology Letters.