Alaska is home to several species of squirrels, demonstrating a remarkable ability to thrive in the subarctic climate. These rodents are not confined to the forested regions but are found across the state’s diverse landscapes, from the open tundra to the dense boreal forests. The presence of both ground-dwelling and tree-dwelling varieties highlights the varied ways these small mammals have adapted. Their survival hinges on specialized behaviors and physiological mechanisms that allow them to endure the long, frigid winters.
Arctic Ground Squirrel: Alaska’s Native Resident
The Arctic Ground Squirrel, Urocitellus parryii, is the most widespread and iconic squirrel species in Alaska. This rodent is the largest ground squirrel in North America, typically measuring between 33 and 50 centimeters in length and weighing up to 1,500 grams. Their robust, cylindrical bodies and short, strong limbs are specifically adapted for their subterranean lifestyle. The squirrel’s fur is tawny brown with pale white flecks on its back, providing camouflage in its preferred open habitats. They inhabit vast areas of northern, eastern, and southwestern Alaska, favoring alpine tundra, meadows, riverbanks, and slopes with loose, well-drained soil.
This specific soil preference is necessary to prevent burrows from being flooded or blocked by permafrost. These ground squirrels are highly social, often living in colonies that utilize extensive burrow systems that can be up to 20 meters long and a meter deep. Their constant digging and burrow maintenance play a significant ecological role by aerating the soil across the tundra landscape. They also serve as a foundational prey source for numerous Alaskan predators, including grizzly bears, arctic foxes, and golden eagles.
Tree and Flying Squirrel Varieties
Alaska’s forested regions, or taiga, support two primary arboreal species. The American Red Squirrel, Tamiasciurus hudsonicus, is a widespread and highly visible inhabitant of the state’s coniferous forests. Unlike its ground-dwelling cousin, the red squirrel is active all winter long and is easily identified as the only diurnal tree squirrel in the region. The second species is the secretive Northern Flying Squirrel, Glaucomys sabrinus.
This smaller, nocturnal rodent glides using a furred membrane called a patagium, which stretches between its wrist and ankle on each side. Flying squirrels are primarily found in forested areas, relying on tree cavities or dense clumps of branches known as “witches’ brooms” for their dens. These two species utilize the rich seed crops of the boreal forest.
The red squirrel is fiercely territorial and defends its food caches, while the flying squirrel’s nocturnal habits mean it is rarely observed by humans. Both species depend on the continuous cover of the forest canopy for both foraging and protection.
Adapting to the Alaskan Environment
Survival in the harsh subarctic climate requires extreme physiological and behavioral adaptations, particularly to endure the long winter season. The Arctic Ground Squirrel is an obligate hibernator, spending between seven and nine months in a state of torpor deep within its burrow. This prolonged period is defined by a drastic reduction in metabolic rate and body temperature.
During the deepest phases of torpor, the ground squirrel’s body temperature can drop to as low as -2.9 degrees Celsius, a phenomenon known as supercooling. This is the lowest body temperature ever measured in a mammal and allows the animal to conserve energy in the frigid environment. To prevent tissue damage, the squirrel periodically wakes up, shivering to rewarm its body temperature back to normal for about 12 to 15 hours before returning to the torpid state.
The energy for this survival strategy is derived primarily from fat stores accumulated during the short summer months. At the lowest body temperatures, hibernating ground squirrels begin to show an increasing reliance on non-lipid fuel sources, which results in a measurable loss of lean muscle mass by the time they emerge in spring. Caching behavior also supports winter survival, as ground squirrels store food in their burrows to sustain them during the initial weeks of spring emergence before new vegetation is available.
Tree squirrels, like the American Red Squirrel, employ a different strategy, remaining active all winter and relying heavily on a large food cache called a midden. This larder-hoarding strategy allows them to access stored conifer cones and seeds without having to forage in deep snow. This combination of deep hibernation for ground squirrels and specialized food caching for tree squirrels illustrates the successful evolutionary paths these small creatures utilize.