Chipmunks and squirrels share a close biological connection, despite their differing appearances. While the term “squirrel” often refers to the tree-dwelling variety, a chipmunk is biologically classified as a type of squirrel. Both are members of the same overarching animal family, which explains their similar behaviors. Understanding the differences in their classification, physical traits, and daily routines illustrates how these two rodents diverged.
The Family Classification
Chipmunks and tree squirrels belong to the same scientific family, Sciuridae, commonly known as the squirrel family. This diverse group also includes groundhogs, marmots, and prairie dogs, all sharing characteristics of small to medium-sized rodents. The major distinction between chipmunks and tree squirrels occurs at the genus level.
Chipmunks are primarily categorized under the genus Tamias, which includes the Eastern chipmunk (Tamias striatus). Common tree squirrels, such as the Eastern Gray Squirrel, belong to the genus Sciurus. This difference in genus indicates a separate evolutionary path and specialization. The genus name Tamias is Greek for “storer,” referencing the chipmunk’s habit of collecting and hoarding food.
Observable Physical Differences
The most immediate difference is size; chipmunks are significantly smaller than most tree squirrels. The Eastern chipmunk typically measures between 6 and 12 inches long, including its tail, and weighs one to five ounces. Conversely, the Eastern Gray Squirrel often reaches lengths of 16 to 21 inches and can weigh up to one and a half pounds.
Chipmunks are easily identified by their striking pattern of five dark stripes running down their backs, separated by lighter stripes. They also feature distinct stripes across their faces, a pattern generally absent in tree squirrels. Tree squirrels, such as the Gray Squirrel, usually have uniformly colored fur (gray, brown, or black) without pronounced stripes. Most tree squirrels possess a long, bushy tail used for balance during climbing, while a chipmunk’s tail is shorter and less densely furred.
Chipmunks possess large internal cheek pouches, extensions of the mouth cavity. These pouches allow them to temporarily hold and transport a large volume of seeds and nuts back to their burrow. Tree squirrels lack these specialized pouches and instead carry food items one at a time or bury them in scattered locations.
Divergent Lifestyle and Habits
The difference in physical form corresponds to a divergence in how these animals interact with their environments. Tree squirrels are predominantly arboreal, spending the majority of their time in trees for foraging, escaping predators, and shelter. They construct nests called dreys high in the branches using leaves and twigs, or they use natural tree cavities.
Chipmunks are largely terrestrial, spending most of their time on the ground and relying on underground burrows for safety and sleeping. These burrows are complex structures that include separate chambers for nesting and storing large caches of food. This intense food hoarding prepares them for true hibernation, where the chipmunk enters a deep sleep state, occasionally waking to feed from stored supplies.
Tree squirrels also cache food but do not undergo true hibernation; instead, they enter shorter periods of torpor during the coldest weather. They remain generally active throughout the winter, relying on body fat and scattered food caches to survive. This difference in winter strategy and shelter highlights the separate ecological niches these two related members of the squirrel family have adopted.