Koalas hugging cool trees can reduce their body temperatures by almost 70 per cent
A KOALA SPRAWLED on the trunk of a eucalyptus isn’t just resting its paws; it’s hugging the tree to stay cool in hot weather, according to researchers from the University of Melbourne.
“If we all had infrared vision, we’d have known all along what koalas are doing,” says lead author of the study Dr Michael Kearney, senior lecturer in zoology at the University of Melbourne.
It was Michael’s student, zoology postgraduate Natalie Briscoe who first stumbled across this phenomenon while measuring the microclimates of koala habitats in south-eastern Australia.
The team had a thermal-imaging camera on hand, and were surprised to discover that the tree trunks – the ones with koalas splayed across them – were on average more than 5°C cooler than the surrounding temperature.
In hot weather animals and birds often avoid overheating via ‘evaporative cooling’. Humans produce sweat, which evaporates and cools the skin in the process.
Animals that don’t have sweat glands often pant like dogs or lick their fur to achieve the same effect. However, for tree-dwelling animals saliva is a luxury they can’t spare.
“Koalas are stuck up on a tree. They pant and lick their fur, but that’s emergency stuff,” explains Michael. “They don’t have much in the way of drinking water. So, if you’re a koala, you want to minimise the amount of water you lose.”