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Arctic Ground Squirrel
Yukon Government Photo
- Distribution
- Characteristics
- Life In and Out of a Burrow
- Arctic Ground Squirrels and People
- Viewing Opportunities
- Interesting Facts
The Species: Spermophilus Parryii
Ears pricked, eyes bright, an arctic ground squirrel stands watch by its burrow. It whistles an alarm as a peregrine swoops, then dives to safety below ground.
Known as a "gopher" to most Yukoners and a "sik-sik" to some, the arctic ground squirrel is a familiar roadside sentinel. It is the largest and most northern of New World ground squirrels.
Distribution
The arctic ground squirrel inhabits tundra and forest clearings from eastern Siberia to Hudson Bay. In North America, its range dips south of the sixtieth parallel only in northern British Columbia, and is widely separated from the ranges of other ground squirrel species.
From southern meadows to the vast arctic coastal plain, sik-siks occur throughout the Yukon from sea level to above 2000 metres. However, the burrowing habits of these chunky ground squirrels restrict them to areas where concrete-like permafrost (permanently frozen soil) lies more than a metre beneath the ground surface.
Suitable ground squirrel habitat has sandy or gravelly soil that makes for easy digging. It also has good drainage to avoid flooding during spring thaw and heavy rains. Eskers, moraines, mountain slopes, river flats and banks, lake shores, and tundra ridges are typical ground squirrel habitat.
As any summer motorist will tell you, gophers seem to be everywhere in the Yukon. However, ground squirrel density depends on the population cycle and on the habitat. In the open Slims River valley of the southwestern Yukon, ground squirrels reach a summer density of six per hectare. However, in spruce forests of the nearby Shakwak Valley, they occur in densities from two down to less than one per hectare.
Characteristics
Short and stocky, the arctic ground squirrel is built for life close to the ground. Its sausage-shaped body, stubby legs, and strong claws are adapted for burrowing. As camouflage amidst the sandy or gravelly soil in which it prefers to dig, the ground squirrel's grey back is dappled with white. The rest of its coat is tawny with cinnamon touches, and its bottle-brush tail has a blackish tip.
A large race of arctic ground squirrels living north of the Porcupine River reaches 40 cm in length and 900 g in weight. This squirrel has fewer and bigger spots on its back than does its smaller cousin (up to 800 grams) living throughout the southern three-quarters of the Yukon. In both races, males weigh about a hundred grams more than females.
Like many other ground squirrels, sik-siks are social animals that live in scattered colonies. Within the colony, dominant males control territories that enclose groups of burrows occupied by females. Females share common ground within a given territory, and don't help males defend territory boundaries.
At the centre of the squirrel's daily life is its burrow. Pocketed with up to 50 entrances and consisting of a maze of multi-leveled tunnels used year after year, the burrow provides a haven from poor weather and predators. Most burrows have a sunny exposure in the lee of prevailing winds, allowing their occupants to take advantage of warmer temperatures in summer and more snow for insulation in winter.
Life In and Out of a Burrow
Winter
Above the tundra's white blanket, winter air lies cold and still. Beneath the snow and a metre of soil, arctic ground squirrels sleep the winter away in nests of dried grasses, lichens, and caribou hair. These nests are tucked into specially excavated dens, known as hibernacula. Placed well within burrow systems and above the level of entrances, the dens are protected both from hungry grizzlies in spring and autumn, and from -40®C air temperatures in winter.
When entering hibernation, a sik-sik rolls itself into a ball by crouching on its haunches, tucking its head down between its legs, and tossing its tail over its head. A true hibernator, it then allows its body temperature to fall to near that of its hibernaculum for weeks at a time. Periodically it warms itself up to near its normal temperature of 36.4®C, then recools within 24 hours.
In the depths of winter, when hibernaculum temperatures drop below freezing, the arctic ground squirrel's body temperature does too. As cool as -3®C, the ground squirrel is, in fact, supercool. The water within its body remains fluid, even though it does not contain any form of antifreeze. Instead, it is able to balance on the edge of freezing only because there is no foreign object (like a speck of dirt or fleck of dust in pond water) around which ice crystals can form. As with other animals, should ice crystals form, the body cells rupture and death may occur.
Arctic ground squirrels are the only mammals known to allow their body temperatures to drop below freezing. By supercooling while hibernating, they save up to ten times the energy needed to stay above 0®C. Such a saving is important in their overall energy budgets. The squirrels hibernate for eight to ten months of the year, so need every bit of stored energy to survive the winter and to start the hectic mating season.
Spring
Driven by the urge to mate, a male ground squirrel rouses himself from hibernation and tunnels up through half a metre of snow to greet our northern spring. With little fresh food available yet, he survives on what's left of his fat and on seeds stored the previous autumn.
With a mating season only three weeks long, male arctic ground squirrels start fighting for breeding territories as soon as they emerge from hibernation in April or early May. Some stay in their present colonies, others disperse to different ones up to a kilometre or more away.
To mark territories, males rub scent from glands on their cheeks and backs onto surfaces along boundaries. Encounters with other males may be of the nosing or pressing-against-each-other kind. Sometimes there's downright shoving that can turn into a chase or boundary brawl. Scratching and biting, fighters roll around in a ball and can receive serious wounds.
Territory winners earn the right to mate with the females residing inside their hard-won space. These females emerge onto the scene one to two weeks after males do, and are ready to mate within a few days. Receptive for as little as one afternoon, they mate not only with resident males, but may also mate with trespassers that slip by the territory owners' defences.
Fresh digging at a female's burrow in May is a good sign that she's making a small natal burrow in which she'll raise her young. Dug from below ground as an extension of her burrow, then blocked off from it, the natal burrow has a single entrance without any sign of the usual ground squirrel dirt mounds.
The young are born as leaf buds unfurl in May and early June. Blind and naked, they each weigh about the same as a couple of quarters. Within two weeks, they wear coats of tawny-grey fur with the characteristic white spots on their backs. At 20 days, their eyes open, and a short time later the young squirrels make their above-ground debut.
Female arctic ground squirrels produce a single litter of five to ten young each year. To protect their offspring, mothers move them to as many as four different natal burrows while they're below ground. Females defend small territories around the natal burrows. They try to hide the burrow entrances from other ground squirrels, and never enter these burrows when strange squirrels are around. A Yukon study has shown that male intruders from other colonies sometimes kill the young in their burrows and occasionally after they're active above ground.
Closely related females bring their young together in one burrow within a few days of emergence from the natal burrows. They share the responsibilities of spotting predators and of protecting young from marauding, non-resident males. Should a predator attack, each of these clustering females may lose fewer young than if only her own were exposed. And, if a female is killed, her relatives may protect her orphaned offspring.
Summer
Wild sweet pea perfume fills the summer air as young sik-siks mock fight and play hide 'n seek. They soon learn to cut plants with their teeth and hold them in both paws to eat. At six weeks they're weaned and already 50 times their birth weight. By late August, they'll be almost full grown, their rapid development reflecting the great productivity of the subarctic summer.
Although the summer sun never sets in parts of its range, this burrow-dweller sticks to a daytime schedule. On cold and rainy days it stays below ground, snug in its burrow. However, on warm days it's out and about, feeding and loafing in the sun as it puts on the extra grams of fat needed to fuel its furnaces through the long winter ahead.
Arctic ground squirrels eat the seeds, leaves, flowers, and berries of a variety of low-growing plants. Some of their favourites are sage, dryas, penstemon, moss campion, asphodel, lousewort, and members of the pea and grass families. In June, they also take to the trees, climbing up into willow bushes to stuff their cheeks with new leaf buds and catkins. Mushrooms and freshly killed animals (including other ground squirrels) are other foods enjoyed by this opportunistic eater.
With juveniles no longer below ground, summer is also a time of movement for sik-siks. Females are active over larger areas, no longer defending territories. Males change territory locations within the colony or emigrate to a different one.
Male offspring disperse from the home burrow, a risky business that increases their chances of being killed by predators or injured in territorial fights. But dispersal decreases their chances of inbreeding. Females, on the other hand, remain near their mothers and suffer lower mortality than males.
When on the move, ground squirrels are often exposed to predation due to lack of cover. They minimize detection by doing the "tundra glide": pressing their bodies close to the ground as they move along. If frightened, they scramble for their burrows and dive headlong into them. And, if caught too far from safety, they may fake a burrow-dive, landing in a thick plant patch instead of a tunnel, then lying still to escape notice. Ground squirrels suffer their greatest mortality in the first year of life, but after that may live to be eight or ten years old.
There are many predators in a ground squirrel's life, including hawks, owls, falcons, eagles, and every mammalian hunter from ermine to grizzly bears. Consequently, they are on constant alert when aboveground. And they have different alarm calls for earthbound and airborne hunters.
If a coyote is spotted, a threatened ground squirrel earns its native name by chattering "sik-sik-sik." Then, as the predator moves closer, the squirrel chatters faster, warning others not only of danger, but of its direction as well. However, should a golden eagle skim overhead, the alarm is a quick, high-pitched whistle that's hard for birds of prey to pinpoint.
Arctic Ground Squirrels and People
In the old days, nearly all Yukon First Nations snared or hunted arctic ground squirrels, enjoyed their tasty flesh, and used their skins to make robes. Southern Tutchone boys and men shot gophers with blunt arrows. Women set long lines of snares around their camps, first in mid-May for a taste of spring gopher, then again in late summer when the sik-siks were at their fattest. They used nooses made from the midribs of eagle feathers, and attached these to thongs of moose or caribou babiche. The skins of snared ground squirrels were peeled off and sewn into women's gopher-skin robes. Indian mothers even sang their babies to sleep with songs of gopher hunting.
Although little trapping is done today, ground squirrels are recognized as an important source of food for valuable furbearers. But to many Yukoners, the ground squirrel's most important role is as the long-awaited harbinger of spring. Its warning whistles and chattering from burrows amidst the snow carry the promise of life's renewal and warmer days to come.
Viewing Opportunities
Drive our roads and highways in summer and you're guaranteed to see arctic ground squirrels. Watch for them feeding, standing upright to scan for predators, or bouncing across the road with head and tail held high. Oh, yes -- be prepared for the daring but indecisive sik-siks to play roadway roulette in front of your vehicle!
For a more natural view of ground squirrel life, check out burrow mounds that you spot while hiking or driving. Listen for alarm calls and look for ground squirrels on watch or diving into their burrows at your approach. Sik-siks often sit on lookouts, such as rocks, brush piles, or burrow mounds. So keep an eye out for their small, upright figures.
Interesting Facts
- Arctic ground squirrels are found on the Yukon's Kaskawulsh nunatak, an isolated mountain separated from other mountains by at least a mile of glacier ice. The origin of this population remains a mystery.
- Grizzlies feast on fattened sik-siks, tearing up huge patches of tundra to dig them out of their winter dens in spring and fall, when green plants are not available.
- In certain parts of the southern Yukon, melanistic or unusually dark ground squirrels are more common than the normal colour phase.
- In a single day, an enterprising arctic ground squirrel was reported to carry away a kilogram of caribou meat.
- The arctic ground squirrel's generic name, Spermophilus, means "lover of seeds", and its specific name, parryii, is derived from that of the famous arctic explorer, Sir William Parry.
- In an old native story from Alaska, the sik-sik dashes into its burrow to escape the raven and calls sharply, "Sit-it!"
