Get Wild: A tale of two rodents
At a picnic area or campsite, you might see what appears to be a giant chipmunk but in fact is a golden-mantled ground squirrel. Both chipmunks and these ground squirrels are omnivores that eat plants, fruits, seeds, nuts and even insects or eggs of ground-nesting birds. Both are prey for hawks, owls, foxes, dogs, cats, raccoons and coyotes. Both carry food in cheek pouches to store in underground burrows for winter. The big differences are in their body sizes and stripes: Chipmunks are smaller, with white and dark stripes on their bodies and heads, and golden-mantled ground squirrels are considerably larger and have wider stripes only on their bodies.
Chipmunks (genus Tamias) and golden-mantled ground squirrels (genus Spermophilus) are members of the huge squirrel family of rodents Sciuridae. They are placed with marmots and prairie dogs in the Marmotini subdivision. These rodents share an ability to rise up on their hind legs and stand fully erect for some time, and they are rather short-tailed compared with other squirrels. Their habitats range from low elevations to above timberline, mostly coniferous or mixed forests, and they especially love areas with shelter, such as rocks, logs and shrubs. During winter hibernation, which can extend from October to May, both enter torpor periods, during which they have low body temperatures, heart rates and metabolic rates that are interrupted by periods of wakefulness.
The least chipmunk (Tamias minimus) is the most common in the Rocky Mountains, and they’re identifiable by dark and pale stripes on their sides, backs and heads. They are 6-9 inches long, weigh 2-3 ounces and live for two to three years. Sexual maturity occurs at one year, and females have litters of five or six offspring in their burrow in late spring. In preparing for winter, chipmunks accumulate fat and store nuts and seeds to consume in their wakeful periods. Chipmunks live mostly on the ground, but they can climb and may nest in hollow trees, too. They are social animals, and they sound alarms if they detect a predator: high-pitched chirps for ground predators and low-pitched clucks for aerial predators.
Golden-mantled ground squirrels (Spermophilus lateralis) are much larger than chipmunks and don’t have any stripes on their heads. They have white rings around their eyes and shorter tails. Most distinctively, the fur on their neck and shoulders is a russet to golden color. They are 9-12 inches long, weigh 6-12 ounces and live about seven years. They have a single litter of four to six offspring in early summer. This ground squirrel’s diet can include lizards, voles and even other small mammals like chipmunks. They are mostly asocial, with males and females inhabiting separate territories except for during mating season. Golden-mantled ground squirrels are usually silent, although they have been known to chirp or squeal to signal predators. They are reported to respond to alarms by marmots, as well. By late summer, with heavy deposits of stored fat, they move into hibernation. While they do arouse from torpor occasionally, they do not eat.
Chipmunks and golden-mantled ground squirrels both have positive impacts on ecosystems, as their digging can help aerate soils and spread seeds. These small rodents provide food sources for numerous larger predators, and golden-mantled ground squirrels may also help regulate the populations of the birds, lizards and small mammals they prey on. While some gardeners consider both rodents pests for eating food crops and bulbs, other people may entice them with feeders to enjoy their antics. However, even though they may provide amusement by begging for peanuts or morsels, please help keep them wild by not feeding them.
“Get Wild” publishes on Fridays in the Summit Daily News. Joan Betz is a board member of Eagle Summit Wilderness Alliance, an all-volunteer nonprofit that helps the U.S. Forest Service protect and preserve the wilderness areas in Eagle and Summit counties. For more information, visit EagleSummitWilderness.org.
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