Many of us will be panting into fan blades and mopping sweaty brows by midsummer. But what's an elephant baking in the sun to do? Thin hair and massive flapping ears help. Now, scientists have identified a third way for the giant pachyderms to cool off: Their hides become more permeable in the heat , according to research published this week in The Journal of Experimental Biology. Scientists measured the heat and moisture released by 13 African and Asian elephants and found that their skin effectively opens up at air temperatures as low as 10°C to 12°C, allowing them to perspire. Most mammals sweat through glands connected to pores, but elephants have pores only between their toes. By making all of their skin permeable, they lose far more moisture via evaporation and are thus able to cool down faster. But they have to drink a lot of water to keep from dehydrating, up to 200 liters per day in the height of summer.