Colorado’s diverse landscape, spanning from the eastern plains to the high alpine peaks, supports a remarkable variety of the rodent family Sciuridae, commonly known as squirrels. This family includes the bushy-tailed tree squirrels, their terrestrial relatives, the ground squirrels, and the diminutive chipmunks. The state’s varied habitats, such as urban parks, high-altitude coniferous forests, and mountain meadows, allow different species to thrive in specialized ecological niches.
The Large Tree Squirrels
Colorado is home to three main species of arboreal squirrels, with the Abert’s Squirrel (Sciurus aberti) standing out due to its unique physical traits. This species is recognized by the long, distinctive tufts of hair on its ears. The Abert’s Squirrel is highly specialized and is almost exclusively associated with mature Ponderosa pine forests, using the trees for food, nesting, and shelter. Its fur color varies considerably, ranging from a salt-and-pepper gray to completely black, particularly along the Front Range.
The Fox Squirrel (Sciurus niger) is the largest and most commonly observed tree squirrel, especially in urban environments and riparian woodlands. Its robust body is covered in fur that is a mix of rusty-red and gray, often with a rusty-colored underside. Unlike the Abert’s Squirrel, the Fox Squirrel does not rely on a single tree species and is highly adaptable, often burying nuts and seeds for later retrieval, which aids in seed dispersal.
The Pine Squirrel (Tamiasciurus hudsonicus), also called the Chickaree, is noticeably smaller than both the Abert’s and Fox Squirrels, typically measuring about a foot in length. This species is highly vocal and often announces its presence with an insistent, chattering scold directed at intruders. Pine Squirrels inhabit higher-elevation coniferous forests, preferring areas with spruce, fir, and lodgepole pines. They are known for creating large caches of cone scales and debris, called middens, where they store cones for winter sustenance.
The Ground Squirrels
Colorado’s ground squirrels lack the large, bushy tail of their arboreal cousins and exhibit seasonal hibernation patterns. The Wyoming Ground Squirrel (Urocitellus elegans) is a medium-sized, brownish-gray species that is often found in open meadows and grasslands at elevations between 6,000 and 12,000 feet. This species is sometimes mistaken for a prairie dog, but it is considerably smaller, with a longer tail and more prominent ears.
Wyoming Ground Squirrels are strictly diurnal and spend a significant portion of their short active season foraging to build up fat reserves for a long hibernation. Adults typically disappear into their burrow systems to begin torpor by late July or early August, remaining underground until the following March or April. Their burrow entrances are often surrounded by a pile of debris, including sticks and rocks.
The Golden-mantled Ground Squirrel (Callospermophilus lateralis) is another common species, often inhabiting rocky areas near campgrounds and edges of woodlands in the mountains. This animal is frequently misidentified as a chipmunk due to the prominent black-bordered white stripes that run down its back. The key distinction is the absence of stripes on the head or face, a feature unique to chipmunks.
The Golden-mantled Ground Squirrel also has a distinct tawny or reddish “mantle” of fur across its neck and shoulders, giving the species its name. This species is found across a wide elevation range, from around 5,200 to 12,500 feet. Like the Wyoming Ground Squirrel, this species hibernates, storing food in its cheek pouches to transport back to its burrow for consumption before and during periods of torpor.
Identifying Colorado’s Chipmunks
Chipmunks are the smallest members of the squirrel family in Colorado and are separated from ground squirrels by a single defining characteristic. Chipmunks possess distinct dark and light stripes that extend forward across their faces, including the eyes. This facial striping is absent in all other striped ground squirrels, such as the Golden-mantled Ground Squirrel.
The Least Chipmunk (Tamias minimus) is the smallest and most widespread species in the state, inhabiting various habitats from low elevations to above the timberline. This tiny rodent has five dark stripes running down its back and sides, with the central stripe often extending from the head to the tail. The Uinta Chipmunk (Neotamias umbrinus) is slightly larger and is mostly limited to the central mountains, often seen in high-elevation coniferous forests.
Chipmunks, like ground squirrels, are burrowing animals and are active during the day, spending much of their time gathering seeds and nuts in their cheek pouches. They are not true hibernators but enter a state of torpor, waking periodically throughout the winter to feed on their stored food caches. Their small size and rapid movements make them a common sight along rocky trails.