Tree-hugging keeps Koalas cool


Tree-hugging helps koalas beat Australia’s heat, research has found. By spreading their bodies out over lower branches koalas are able to absorb the cooler temperatures that occur inside trees and reduce their core temperature. This not only makes them more comfortable but also increases their chances of surviving the intense heatwaves that take place in Australia. Unlike other animals, koalas do not use hollows or dens for shelter but rather spend their time exposed to the sun.

“They’re just stuck out on the tree all the time so when hot weather comes they’re completely exposed to it,” Dr Michael Kearney from the University of Melbourne’s zoology department told Guardian Australia. “When a heatwave comes the most effective way for the koala to lose heat is through evaporation. They don’t sweat but they can pant and lick their fur.” However, in times of intense heat and low rainfall, koalas cannot maintain the evaporation rates needed and have to seek other ways to remain cool.

The scientists studied around 30 koalas on French Island, near Melbourne. At times of extreme heat they witnessed them lying flat out along the branches, which is an unusual stance for them.


Thermal image of a koala hugging the cool lower limb of a tree, illustrating a posture typically observed during hot weather

“I sort of see it as, ‘Oh I’m so hot, I’m going to lie down’, but there’s more reason to it than that,” said Kearney, a co-author of the report. “The fur on their tummy is quite a lot thinner than the fur on their backs, so they’re pushing that fur and that part of their body as much against the tree as possible. “Any way that they can lose heat that doesn’t involve losing water is going to be a huge advantage to them. Dumping heat into the tree is one of those methods.”

The team fitted radio collars to the bears so they could track them during the day in both winter (June–August 2009) and summer (December–March 2010 and 2011). They then used thermal imaging technology to confirm and further examine their observations.


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