Why Do Koalas Hug Trees?

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Just as we humans cling to our air conditioners and plunge our heads into the freezer in the summer months, koalas have found a source of relief from stifling temperatures. According to a recent report, those cute, eucalyptus-eating marsupials keep cool by hugging trees.

Wild koalas live in parts of Australia where the temperatures regularly soar well over 100 degrees Fahrenheit. Natalie Briscoe, a research fellow at the University of Melbourne, fitted a group of 37 koalas with radio collars and studied them through both warm and cool months. She noticed that, when the heat rises, the animals descend from the eucalyptus limbs and wrap themselves around the trunks of the trees. Perplexed, Briscoe and her colleague Michael Kearney whipped out infrared cameras to measure the koalas’ temperatures, and upon doing so, discovered "it was absolutely obvious what they were doing," says Kearney. The trunks appeared much cooler than the surrounding air, probably because the trees suck water up through their roots. The koalas would even hug Acacia mearnsii trees, which they don’t eat, but which have even colder trunks.

For an animal that rarely drinks water (koalas get much of their water from eucalyptus leaves) and is covered in fur, chilling out is important. The animals don’t sweat, but when they pant or lick their fur to cool down, they lose moisture. So the warmer they are, the more water they lose. Researchers think the trunk-hugging koalas lose half as much water as they otherwise would.

And koalas aren’t the only tree-huggers. Leopards, primates, birds and other creatures could be using trees to combat colossal heat in ways we don’t yet know. Learning how animals use trees to manage their temperatures helps researchers understand how they will adapt to climate change.