How Reindeer Keep Their Cool

Scientists found out how these mammals avoid getting too hot.

Reindeer are made for frigid Arctic winters. But unlike humans, who can shed clothing when heat strikes, they can鈥檛 remove layers. Yet reindeer don鈥檛 burn up when running from predators in deep snow.

To figure out how the mammals chill out, scientists trained nine female reindeer (less temperamental than males) to run on a treadmill. They then observed their reactions as they heated up, finding that the animals rely on a three-pronged approach to keep their cool.

First, they pant, close-mouthed. If their temperature continues to climb, they stick out their tongues to evaporate saliva and cool the blood. 鈥淥nly in extreme conditions鈥濃攚hen brain temperature hits 102 degrees鈥斺渄o they activate the third stage of defense,鈥 says Arnoldus Schytte Blix of Norway鈥檚 University of Troms酶, who published the findings in .

The trick: 鈥淐old blood from the nose selectively cools warm blood en route to the brain,鈥 a heat transfer that prevents a possibly life-threatening two-degree rise in brain temperature. No doubt about it鈥攔eindeer stay cool under pressure.

This story originally ran in the as "Chill Out."