This morning the loud chirping of an arctic ground squirrel woke me up. These sizable rodents (New York City squirrels wouldn't stand a chance against them) are darting all over Toolik Field Station. The rule is "Don't feed the wildlife" but it's known that they’re partial to carrots because that's what researchers use to lure them into live traps in order to study them (apparently, they fall for it time and time again—maybe being handled a bit is worth the tasty snack). While the two squirrels in this video are quite active right now, the animals spend up to 10 months hibernating. The only mammals known to drop their body temperatures below freezing, they survive winter in a "supercooled" state at -3 degrees C.
They manage this by cleansing their blood of anything around which ice crystals can form; if ice crystals were to form, cells would rupture and death would likely follow. The squirrels do increase their body temperature and metabolic rate every 20 days or so for about 12 hours. Scientists aren’t sure why they do this, but zoophysiologist Brian Barnes believes the rodents might warm up because they’re sleep deprived—their brainwaves are flat when their body temps dip below zero, but when they turn up the heat for a half-day, their brainwaves show that they’re sleeping for most of that time. Perhaps they’re dreaming of carrots?