Koalas Hug Trees to Cool Themselves Down in Hot Weather

Posted on June 5, 2014

Scientists say koala bears hug trees in order to reduce their body temperature. University of Melbourne researchers studied 30 koalas during hot weather. Natalie Briscoe, the leader researcher of the study from the University's School of Botany, says koalas were observed hugging cool tree trunks, which can be as much as 5 degrees Celsius cooler than the air during very hot days. A thermal image of a koala hugging a tree is pictured above.

Briscoe says in a statement, "We found trunks of some tree species can be over 5°C cooler than the air during hot weather. Access to these trees can save about half the water a koala would need to keep cool on a hot day. This significantly reduces the amount of heat stress for koalas."

The researchers used a portable weather station attached to a long pole to measure what koalas were experiencing in the places they chose to rest in the trees. They found areas of the trees can act like a micro climate. The L.A. Times reports that the coolest trees of all the trees tested were the Acacia mearnsii trees. Koalas spent 29% of their time in these during the summer, but just 5% of their time in them during the cooler winter.

Dr. Michael Kearney, a co-author of the study, says, "When we took the heat imagery it dramatically confirmed our idea that 'tree hugging' was an important cooling behaviour in extreme heat. 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."

A research paper on the study was published here in Biology Letters.

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