Ground Squirrel
Kristee Summerford
Eastern chipmunks and 13-lined ground squirrels are both rodents. They have brown, grayish-brown or reddish-brown fur and are generally similar in size. Chipmunks are usually about 10 inches long, while ground squirrels range from 6 inches to 12 inches.
The most telltale difference between the two is the presence of stripes on their heads, or lack thereof. While both are striped, only 13-lined ground squirrels have stripes that extend to their heads. Only the bodies of eastern chipmunks are striped.
Their stripe pattern can also be used to differentiate them. Thirteen-lined ground squirrels are appropriately named for their 13 narrow stripes. The lines are actually alternating stripes, with seven dark brown stripes and six tan stripes, according to the University of Michigan's Animal Diversity Web. The dark brown stripes also usually have tan spots, giving them a dotted appearance. Chipmunks, on the other hand, have five wider stripes alternating between brown and tan.
Where you see them can also be telling of whether you are seeing a ground squirrel or a chipmunk. Ground squirrels prefer grassy areas such as yards, cemeteries, golf courses and pastures, and they generally avoid wooded areas. Chipmunks, on the other hand, prefer wooded areas and forests and are also often seen along the edges of wooded areas and in yards with plenty of trees and shrubs.
Both chipmunks and ground squirrels are active during the day, and both are busy at this time of the year as they prepare to hibernate for winter. But only the ground squirrel is a true hibernator, spending all but three to four months a year underground, according to the Missouri Department of Conservation. Chipmunks hibernate as well, but not in the truest sense. They spend most their time during winter underground sleeping in their burrows, but they wake to eat every few days.
Chipmunks and ground squirrels are both omnivores. Chipmunks eat primarily seeds, nuts and berries, while ground squirrels eat mainly seeds and plant material including agricultural plants like corn and wheat. Both occasionally eat insects and small animals.
One key difference between the two is that only chipmunks store food for winter. They'll gather nuts and seeds to store in their burrows to feast on during winter. Ground squirrels do not wake during their hibernation, so they have no need to create food stores. Instead, during the fall they double their body weight to increase their fat stores to live off during winter, the Missouri Department of Conservation reports.
While chipmunks and ground squirrels can be hard to tell apart, they are easy to distinguish from another common relative: tree squirrels. With their big, bushy tails, tree squirrels can be readily identified.
Illinois is home to several tree squirrel species, including eastern gray squirrels and eastern fox squirrels. The fox squirrels are the larger of the two, but you can most easily tell them apart by the fur on their bellies. Fox squirrels have reddish-brown underbellies, while gray squirrels have white underbellies, according to Wildlife Illinois.
Why it's awesome: Rumor has it that tufted ground squirrels, nicknamed "vampire" squirrels in a 2014 Science article, jump down from low branches onto the backs of deer and kill them by slashing the jugular vein with their razor-sharp teeth.
Local Dayak hunters report finding disemboweled deer carcasses and suspect the squirrels feast on their prey's stomach content, heart and liver. In villages close to the forest edge, tufted ground squirrels are also said to kill domestic chickens to eat their hearts and livers.
Uinta ground squirrels are sometimes mistaken for prairie dogs. They hibernate for most of the year, coming above ground in the spring and early summer to feed on lush vegetation. Duration: 2 minute 13 seconds
Arctic ground squirrels are the largest of the North American ground squirrel species, ranging from 524 up to 1,500 grams in weight, and 332 to 495 mm in length. They undergo seasonal changes in body mass and lose weight during hibernation. They exhibit sexual dimorphism, with males being larger than females. Body mass drastically varies seasonally, between summer foraging bouts and winter hibernation. They have tawny brown coloration with white flecks on the dorsal side of the pelage and a light tan or beige coloration on their undersides. Their undersides lighten during winter months.
Cylindrical in shape with short, strong forearms and hind legs, the arctic ground squirrel is built for burrowing and digging. They have sharp claws and soft pads on the undersides of the hands which aid them in manipulating food and dirt. Their heads and ears are rounded, and their tails are relatively short compared to other squirrel species.
Mating season for arctic ground squirrels occurs in late April to early May, after they awake from hibernation. Males aggressively defend territories with multiple females, displaying a polygynous mating system. Males seeking to expand or find new territory will often engage in infanticide. Females will group together after breeding in kin clusters which are thought to provide a higher level of protection from infanticidal males, in addition to protection from predators.
Males display a significant trade-off between survival rate and reproduction. Their aggressive territorial behavior produces raised stress levels that can result in up to 21 percent lowered body mass, and compromised immune systems. These compromises in body conditions result in a high mortality rate in male arctic ground squirrels after breeding season, and the ratio of females becomes much higher than males after breeding season.
Arctic ground squirrels are highly opportunistic feeders. They have a widely varied diet which includes vegetation such as stems and leaves, roots, fruits, seeds, flowers, grasses and sedges, and other green or woody plants, as well as mushrooms. Along with vegetation, arctic ground squirrels are known to eat eggs, invertebrates, and small vertebrates including juvenile snowshoe hares, collared lemmings, and even their own young. Food is stored or cached only by male arctic ground squirrels in burrows for arousal from winter hibernation.
As an adaptation for coping with the harsh, inclement weather of the winter months, arctic ground squirrels hibernate for about eight months out of the year. Their chosen hibernacula have coverage provided by vegetation, rather than open, windswept burrows. This vegetation coverage allows for a higher accumulation of snow and warmer soil temperatures.
The arctic ground squirrel ranges across northern, eastern, and southwestern Alaska at elevations ranging from sea level to well above mountain tree lines. It is the only ground squirrel species in its range. They occur in tundra, meadow, riverbank, and lakeshore habitats with loose soils that provide early vegetation.
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