Why do koalas hug trees? Not, as it turns out, because its makes them look cute. Instead, it's an example of what some call "environmental intelligence:" they hug trees to stay cool on hot days, reducing their body temperature by up to 70%! Trees are much better at beating the heat than furry mammals, because trees conduct cool groundwater from the earth through their trunks and limbs.
In this study, a team of researchers labored arduously through days of watching what is widely known as the world's cutest animal and taking temperature measurements. They found a clear pattern: on mild days, koalas are more likely to curl into a ball or perch on a limb near the top of the tree. On hot days, they adopt their classic tree-hugging pose, moving down to the trunk: through conductive heat transfer, the tree gets a little warmer and the koala gets a lot cooler. (The paper detailing their results includes the most adorable chart ever to be published in a peer-reviewed journal.)
In comparison, our method of staying cool-- air conditioning units-- has dire effects. Pound for pound, gases used for AC "contribute to global warming thousands of times more than does carbon dioxide, the standard greenhouse gas." And as global demand for AC rises (in part because it is indicative of middle-class status), emissions will continue to rise.
In short, we could do well to learn from the koala: ditch the AC and go hug a tree!
In a new paper in the Royal Society’s Biology Letters, a team of Australian and American researchers report that as temperatures rise, koalas tend to put more of their bodies in contact with the trees they inhabit. The science behind this involves something called conductive heat transfer, wherein a warm object (say, a koala) transfers heat to a cooler one (like a tree) and both objects approach the same temperature. The trees stay cool by sucking up water hidden deep in the soil from the baking sun.