Australasian Science: Australia's authority on science since 1938

Tree-Hugging Keeps Koalas Cool

Thermal imaging has revealed that koalas cope with extreme heat by resting against cooler tree trunks, according to research published in Biology Letters.

“We found trunks of some tree species can be more than 5°C cooler than the air during hot weather,” said lead author Natalie Briscoe of The University of Melbourne. “We know koalas also pant and lick their fur to cool down, but that can lead to dehydration. Access to these trees can save about half the water a koala would need to keep cool on a hot day.”

Researchers used a portable weather station on a long pole to measured what 30 koalas on Victoria’s French Island were experiencing in the places they chose to sit, and compared this with other places available to them.

Co-author Prof Andrew Krockenberger of James Cook University said that heat wave events can hit koala populations hard. “About a quarter of the koalas in one population died during a heatwave in 2009,” Krockenberger said. “Understanding the types of factors that can make some populations more resilient is important. Access to cool tree trunks would significantly reduce the amount of heat stress for koalas.”

Co-author Dr Michael Kearney of The University of Melbourne said that “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.”