Just as humans relish the chance to flop down upon a cool bed sheet on a warm day, koalas escape the summer sun by sprawling out on a cool branch.
Of course, koalas don't hang out in trees to keep cool; they live where they do for the sustenance and for the safety it provides from predators. Koalas love trees as a place to eat leaves and raise their young. But when its extra steamy outside -- as a new study in the journal Biology Letters explains -- the cooler temperatures deep inside a tree also help to moderate the koalas' body temperatures.
"They're just stuck out on the tree all the time so when hot weather comes they're completely exposed to it," study co-author Dr. Michael Kearney, a zoologist at the University of Melbourne's, recently told The Guardian. "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."
And while collapsing frontside-down on a branch may look lazy, it's pretty smart. The fur on a koala's belly is much thinner, allowing for more efficient displacement of heat.
"Our modeling shows that hugging a cool tree trunk during a typical hot day in southeastern Australia can halve the amount of heat koalas need to lose via evaporative cooling," said co-author Natalie Briscoe. "This behaviour is likely to help them cope with hotter or longer extreme heat events."
Other animals have demonstrated similar cooling behaviors, including leopards, as well as some species of birds and insects.