Trees Become Refrigerators For Koalas

Written by: Lisa Stelzner

Primary Source: Daily Dose of Science Blog

Have you ever wondered if there is a reason why koalas look like they are hugging trees by wrapping their arms and legs around them?  It turns out there is a big benefit to this behavior – on hot days, trees are cooler than the surrounding air, so when koalas “hug” them, they are staying cooler. Also, although koalas only eat eucalyptus leaves, scientists found them on acacia trees a third of the time on days over 35 degrees C.  Scientists found that acacias were 5 degrees cooler than eucalyptus trees on those days.  This is very important information for designing koala reserves or zoo exhibits, because more than just eucalyptus trees should be included. Koalas are often in danger of overheating and dehydration (they only get their water from eating leaves), and can’t sweat, but their fur on their stomachs is thinner than on the rest of their bodies, so by pressing their stomachs against the trees, they get the maximum cooling benefit.


A thermal image taken by scientists shows how much cooler trees are than their surroundings on a hot day.  Photo credit: Steve Griffiths
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Lisa Stelzner
I'm a plant biology PhD student studying monarch butterflies in Michigan, but I'm interested in lots of other types of science, too. I am interested in how breeding monarch butterflies choose their habitat based on floral species richness and abundance. Few studies have been conducted on optimal foraging theory when it involves an organism searching for two different kinds of resources, and butterflies are an ideal study system to investigate this, since many species are ovipositing specialists and only lay eggs on one species of hostplant, but are feeding generalists and nectar from a broad variety of flowering forbs.