Koalas hug trees to lose heat
Hugging trees helps koalas to keep cool, a study has revealed.
In a study published in the Royal Society journal Biology Letters, scientists used thermal cameras to reveal that, in hotter weather, the animals moved to the lower, cooler parts of the trees. They also pressed their bodies even closer to the trunks.
The team, led by researchers from the University of Melbourne, was studying how koalas regulated their temperature. This is part of a wider research project investigating the effect of climate on land-dwelling animals in Australia, a country which experienced an extreme heat wave earlier this year.
While PhD student Natalie Briscoe was studying the koalas' behaviour, she noticed that
in the winter the animals would stay high in the trees - up near the leaves feeding. In the hotter summer weather though, they would move down.
Dr Michael Kearney from the University of Melbourne explained: "They'd just flop over the [lower] tree trunks. "It looked like they were spread-eagled and uncomfortable; it seemed like the wrong thing to do."
But measurements of the temperatures of the tree trunks showed that, on days as hot as 39C,
they were up to seven degrees cooler than the air.
That's what made us wonder if the koalas were using the trees as a heat sink," said Dr Kearney.
The team used a thermal camera to take pictures of koalas on a particularly hot day.
"When we got the images, back it was so obvious what the koala was doing," explained Dr Kearney.
"You could see the koala sitting on the coolest part of the tree trunk with its bottom wedged right into
the coolest spot.
Dr Kearney said large trees had their own protective "microclimate", which is likely to become increasingly important to tree-dwelling creatures like koalas if global temperatures continue to increase as predicted.
"This helps them to maximise their chances of survival during extreme heat events,"
Research Dr Welbergen published earlier this year revealed the effects on wildlife of such extreme events.
Research revealed that 45,500 flying foxes had died on just one extremely hot day in southeast Queensland.
Hugging trees, Dr Kearney said, helps the koalas to avoid similar water loss - enabling them to "dump heat" into the tree and to avoid panting.