Koalas are the original tree-huggers

Koalas keep their cool by hugging trees, new research has shown.

Armed with thermal-imaging cameras, Natalie Briscoe and her colleagues at the University of Melbourne found that these animals, which are considered to be a critically endangered species, use the cooler trunks of their host eucalyptus trees as heatsinks.

By wrapping themselves tightly against the larger, shadier tree limbs koalas are able to exploit the temperature difference between the wood and the surrounding air, which can be up to seven degrees Celsius, helping them to shed excess heat.

Although the animals can also pant like dogs to keep their temperatures down, this leads to so called "insensible" water loss in breath, so using the tree is a superior, water-sparing option. Predictably, koalas also vary this behaviour with the season, exploiting the cooling effects of the trees more at hotter times of the year.

The research, published this week in Biology Letters, highlights the importance of considering how climate change might impact the animals in the future. If higher average temperatures force them to retreat down trees more often, this could have nutritional and reproductive costs.

At the same time, the trees that afford the animals the greatest cooling benefits are also the largest ones, meaning that conservation efforts need to focus on both the animals and the preservation of their habitats.