marsupials don't retreat to dens or dugouts to keep cool.]]> exposed more of their surface area.]]> calculated that a 25-pound male koala could shed 68 percent of its excess heat on a 95-degree day by hugging a cool tree in a shady spot.]]> species of trees - three eucalyptus and one acacia - at the peak of summer.]]> Biology Letters.]]> strategy for chilling out.]]> excess heat on a 95-degree day by hugging a cool tree in a shady spot.]]> preferences for high or low branches.]]> asset.]]> conducts heat.]]> plausible, they came up with an equation to determine just how much heat a koala could shed by hugging a cool tree.]]> ingenious strategy for chilling out.]]> ventured higher up in the tree and farther out onto the branches.]]> scarce.]]> theory was plausible, they came up with an equation to determine just how much heat a koala could shed by hugging a cool tree.]]>