A ground squirrel built to freeze without dying
Most hibernating mammals keep their core body temperature just above freezing. The arctic ground squirrel doesn’t stop there. During the depths of an Alaska winter its body temperature can drop below the freezing point of water for weeks at a time. That’s among the coldest body temperatures ever recorded in a mammal, and it still wakes up again come spring. That single trick is what lets this species live where almost no other ground squirrel can. It holds tundra and permafrost soils from Alaska’s North Slope down through interior river valleys, ground that would kill most burrowing mammals over winter.
Telling an arctic ground squirrel from the crowd
Look for a rusty, cinnamon-tan coat scattered with small, indistinct pale spots across the back, a build stockier than a tree squirrel’s, and a much shorter, less bushy tail. It stands bolt upright on its hind legs at the first hint of trouble, a habit it shares with prairie dogs and other ground squirrels farther south. Nothing else sharing its Arctic and subarctic range looks quite like it.
Where, and when, to expect one
Records cluster on well-drained, sandy or gravelly ground: river bluffs, eskers, tundra slopes, and lakeshores, anywhere the soil is loose enough to dig through without hitting permafrost right away. That’s not a small requirement in the Arctic, and it shapes where colonies can exist at all. Sightings build fast in spring, peak in July, then taper off through September and vanish completely from October through March. That pattern isn’t just sampling bias. For roughly seven months of the year, every arctic ground squirrel in Alaska is asleep underground.
A short, frantic summer
Above ground, arctic ground squirrels are active only in daylight, and records climb through the middle of the day rather than at dawn or dusk. There’s a reason for the urgency. A squirrel that emerges in spring has only a few months to feed, mate, raise a litter, and pack on enough fat to survive the winter that’s coming. Litters run five to ten young after a gestation of about 25 days, about as fast a turnaround as a rodent this size can manage. There’s no time to waste on a slow start.
Diet, and its place in the food web
Arctic ground squirrels eat mostly plant material: tundra grasses, sedges, berries, and roots, whatever grows fast enough in a short summer to be worth harvesting. They round that out with animal matter when they find it, insects, bird eggs, and occasionally other small vertebrates. That opportunism runs both ways. This is one of the most important prey species across its range, hunted from the air by golden eagles, northern harriers, and short-eared owls, and from the ground by red foxes, wolves, and wolverines. A poor year for ground squirrels can ripple through the whole predator community that depends on them.
Common questions
How cold does an arctic ground squirrel’s body actually get during hibernation? Researchers have recorded body temperatures below freezing for extended stretches, among the most extreme cold tolerance known in any mammal. It still periodically rewarms itself before settling back down.
Are arctic ground squirrels social? They live in loose colonies rather than tight family groups, and they give sharp alarm calls when a predator appears, a habit that warns every squirrel within earshot at once.
What eats arctic ground squirrels? A long list of Arctic predators, including golden eagles, red foxes, wolves, and wolverines, rely on them heavily, especially right after young squirrels first emerge from their burrows in early summer.
