How Do Squirrels and Other Critters Stay Cool?

During the hot summer heatwave, while the rest of us are thinking of swimming pools and ice cream, Brian Palmer of Slate is thinking of squirrels. More specifically, do squirrels and pigeons get sweaty? How do animals beat the heat?

While most animals don't sweat very much, many species rely on the principle behind sweating to keep cool: Moisture on the skin absorbs heat and evaporates, carrying away unwanted warmth. Animals that lack sweat glands just have to find a different way to bring air into contact with moist skin. Many creatures pant, drawing air across their damp tongue. Pigeons employ a variation called gular fluttering, vibrating their throats. Birds and rodents spend a lot of time licking themselves. Squirrels tend to focus the saliva bath on the forearms, where the fur is thin and the blood flow is higher. Some birds even urinate on their legs to evaporate the heat away.

How about squirrels?

Squirrels also use their tails for thermoregulation. Ambient air chills the blood in the thin tail quickly. In the summer, the squirrel pumps the cooled blood directly back into the torso to lower its internal temperature. In the winter, the circulatory route changes slightly, so that the chilled blood coming back from the tail is heated by the warmer outbound blood before contacting the squirrel's organs. (The tail also serves as a pretty good blanket on a frigid night.) You may see squirrels running around with their tails flipped up over their bodies in the summer. This is because the lighter-colored underside of the tail absorbs less heat from the sun than the darker dorsal side, and it shades their bodies like a parasol.

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