Arctic ground squirrel

The Arctic ground squirrel (Urocitellus parryii) (Inuktitut: ᓯᒃᓯᒃ, siksik) is a species of ground squirrel in the squirrel family Sciuridae that is native to the Arctic and Subarctic regions of the Northern Hemisphere, mainly in North America and Asia. For some people in Alaska, particularly around the Aleutian Islands, the rodents are known as "parka" squirrels, likely due to their pelts being used for the ruff on parkas and other cold-weather clothing.

Subspecies listed alphabetically.

The Arctic ground squirrel typically has a beige-tan pelage with a lightly spotted backside. Similar to the related prairie dog, it has a shorter face than the typical arboreal squirrels–due to its lifestyle of burrowing–as well as smaller ears, with a dark tail and white markings around the eyes.

During the brief boreal summer, Arctic ground squirrels undergo an annual molting (coat shedding/re-growth) cycle in preparation for the onset of colder weather; this is seen in other Arctic species, as well, such as the white winter coat of the Arctic fox, Arctic and snowshoe hares, ermine (stoat), and even some birds, such as the rock ptarmigan. Summer coats include reddish and yellow colorations along the cheeks and sides of the body; in the fall, these red patches are shed and replaced by a more silvery color. The lighter coloration in winter helps the ground squirrels to camouflage against the often snow-white ground and better evade predators, such as snowy owls or foxes. The average length of an Arctic ground squirrel is approximately 39 cm (15 in). Since Arctic ground squirrels undergo drastic seasonal changes in body mass, it is difficult to give an average mass; adult females are close to 750 g (26 oz), while males may weigh nearly 100 g (3.5 oz) heavier.

The Arctic ground squirrel can be found in parts of western Northern Canada, from the Arctic Circle to the Yukon, northern British Columbia and the Northwest Territories; west into Alaska, the Alaska Peninsula, the Aleutian Islands archipelago, and across to the Russian Far East (Siberia), including the Kamchatka Peninsula. The St. Lawrence Island subspecies (U. p. lyratus) of Arctic ground squirrel is found on its namesake island in the Bering Sea; the Kodiak Island subspecies (U. p. kodiacensis) is found on Kodiak.

The Arctic ground squirrel has evolved with and is found on the North American Arctic tundra; depending on the subspecies, its preferred habitats are typically hillside or mountain slopes, riparian areas (such as river flats, banks or lake shores) or tundra ridges. Arctic ground squirrels prefer to live in sandy soil due to its ease of manipulation for burrowing, and its superior drainage as opposed to richer soils. Arctic ground squirrels make shallow tunnels and burrows in locations where the permafrost will not prevent them from digging. The more southerly subspecies typically inhabit open meadows and open tundra habitats.

The Arctic ground squirrel has an extensive fossil record from the Pleistocene. During the Last Glacial Maximum, it was abundant in areas such as the Klondike region where it is currently rare or absent. Fossilised Arctic ground squirrel nests and caches have also been used for palaeoenvironmental reconstruction; Calamagrostis canadensis, Carex albonigra, and Koeleria sp. are common in caches from Late Pleistocene Alaska, indicating the presence of an aerially extensive mammoth steppe ecosystem in the region at this time.

The diurnal Arctic ground squirrel lives on the tundra, where it may fall prey to the Arctic and the red fox, wolverine, Canada and Eurasian lynx, brown bear, snowy owls and eagles. It is one of the few Arctic mammal species which hibernates in the winter, similarly to the little brown bat and the closely related marmot. In the summer, it forages for tundra plants, seeds, and fruit to increase body fat for its winter hibernation. By late summer, the male Arctic ground squirrel begins to store food in its cache so that, come springtime, it will have a food source until the any new vegetation has grown. Their burrows are lined with lichens, leaves, grasses, and muskox hair, amongst other animal fibers they may find.