Squirrels and chipmunks are often mistaken for each another. That shouldn’t be a surprise since the two are closely related. Squirrels and chipmunks are part of the order Rodentia which comprises over 1650 species; the biggest group of living mammals. There are over 365 species of squirrels and 25 species of chipmunks. They have many similarities. But that doesn’t mean they are exactly alike; they do have defining differences. The most common squirrel in the United States is the gray squirrel and the most common chipmunk is the Eastern chipmunk.
The Eastern chipmunk looks very different from the gray squirrel, and they can't be mistaken for each other. The Eastern chipmunk is a small mammal ranging in size from about 5 to 6 inches long and weighing up to 3 oz. The gray squirrel is much larger, ranging in length from 16 to 22 inches long and weighing up to 2.5 lbs.
Chipmunks are a brown-reddish color with distinct stripes; they have five black stripes on their backs and two white stripes on their heads and beneath the eyes. The gray squirrel ranges in color between light to dark gray and it has no stripes. They are easily distinguished by large bushy tails that are usually a paler white gray. The chipmunk has a small tail that sticks straight up like an antennae.
Eastern chipmunks and gray squirrels prefer different living environments. Chipmunks like to make burrows beneath the ground near rocks or along tree roots. The burrow is used to store food and is lightly padded with leaves for resting and nesting. Gray squirrels spend the majority of their time up in trees. The trees provide them with the nuts they enjoy eating and also protect their nests. You can find gray squirrels living in tree cavities that offer plenty of protection from predators.
One distinguishing characteristic between chipmunk and squirrels (not ground squirrels) are internal mouth pockets. A chipmunk has internal pockets in its cheeks. The chipmunk can store food within the pockets to carry back to its burrow. This allows the animal to forage and carry more food back to its home. Most squirrels do not have these pockets. They prefer to fatten up for the winter months instead of foraging for food like the chipmunks.