Chipmunk

Working in my office upstairs one morning, I heard scratching from the fan in the adjacent bathroom. I couldn’t spot anything unusual. I hollered for Zell, who immediately suspected some critter had gotten into the fan vent. On the roof, he found that the plastic grill that covered the vent opening had been chewed through. Given the size of the opening and the likely suspects in our area, we figured that chipmunks were likely trying to nest in the fan vent. Geez—you’d think with 100+ nest boxes on the property, they’d choose something less problematic. But they hadn’t, so we needed to evict them ASAP. I held burning paper towels up to the opening of the fan in the bathroom to smoke them out while Zell parked himself on the roof by the vent to see when they left. (Very high-tech and cutting edge, I know.) It didn’t take long until several chipmunks emerged from the vent and scampered down the roof. Zell then replaced the ridiculously flimsy plastic grill with a heavy-duty metal grill. Except for the time they chewed through the Internet satellite cable on the roof a few years later, we’ve had no major chipmunk issues since then.

The smallest of the squirrels, chipmunks can be differentiated most easily from other striped squirrels (e.g., the thirteen-lined ground squirrel or the golden-mantled ground squirrel) by their striped faces, since other squirrels have unstriped faces. Aside from that distinction, chipmunks can be difficult to identify to specific species. Colorado hosts 5 species of chipmunk, all of which look pretty much alike as they scamper away from you. In our area, Colorado and least chipmunks are the most likely species. One characteristic suggested for differentiating these species is to watch an individual’s tail. Colorado chipmunks tend to move their tails from side to side when they are chattering or running; least chipmunks hold their straight up in those situations. Given this distinction, I’d guess that the chipmunks in the arid pinyon/juniper habitat around our house are Colorados. Depending on your habitat, your results may vary…

Unlike most other squirrels, chipmunks have internal cheek pouches for carrying food. Their diet consists primarily of vegetation: stems, buds, seeds, leaves, flowers, and fruits from a wide variety of plants. However, they’ll also eat insects, small invertebrates, and bird eggs and small nestlings if the opportunity arises. Chipmunks are members of the vast order of mammals called Rodentia, the largest and most diverse group of mammals on the planet. More specifically, the Sciuridae (squirrel) family includes marmots, prairie dogs, chipmunks, ground squirrels, and tree squirrels. As with all rodents, a chipmunk’s teeth grow continually throughout its life. (In fact, the word “rodent” derives from the Latin rodere, meaning “to gnaw.”) It has to chew constantly to both wear down and hone its front teeth into sharp little chisels. Hence our destroyed fan vent grill and satellite cable.

Chipmunks in Colorado have a single litter of 5 – 8, born in early summer after a 30-day gestation period. They typically make grass-lined nests in burrows, although I often find them nesting in our nest boxes, using strips of juniper bark instead of grasses. Raised by the female, the young are weaned and independent with 2 months after birth—right about now.

In autumn, chipmunks gather vegetation as a supply of winter food. Some species keep this stash in their burrows, which can be more than 10 feet in length. Chipmunks hibernate in winter. When a chipmunk is in the deep sleep phase of hibernation, its heart rate declines from about 350 beats per minute to perhaps 4. Its body temperature may drop from 94 degrees F to whatever the temperature of the burrow—as cold as 40 degrees F. But they wake every few days, raise their body temperatures to normal, feed on stored food rather than drawing on fat reserves (as hibernating bears do), and urinate and defecate (as hibernating bears do not, interestingly enough).

The Colorado chipmunk’s scientific name, Tamias quadrivittatus, derives from Greek “tamias” (“hoarder”) for its storing of seeds for winter use and Latin “quad” (“four) and “vitta” (“ribbon”)—perhaps referring to the 4 stripes on the side of its face. The common name is believed to come from the Ottawa language (“jidmoonh”), meaning “red squirrel.

An Iroquois legend offers a suggestion about how the chipmunk got its stripes. Chipmunk was persistently teasing Bear about one thing or another, when Bear grabbed him, trapping Chipmunk under his big paw. Chipmunk used his cleverness to escape before Bear could eat him—but not without Bear’s claw marks as a perpetual reminder of Chipmunk’s cheeky demeanor and narrow escape.

You can learn a bit more about chipmunks here.