There are eighteen species of squirrels in Rocky Mountain National Park. All are diurnal so they are seen frequently and are the best known of the small mammals in the park.

Least Chipmunk
Golden-mantled Ground Squirrel
Wyoming Ground Squirrel
Chickaree
Abert's Squirrel

NPS Photo

Least  Chipmunk

The least chipmunk is the smallest squirrel in the park ranging in length from less than seven inches to nine inches. They can be identified by a gray belly and nape of neck. The most apparent feature is the five stripes on the back and sides of their small bodies. Two of the stripes extend onto the head. Only the chipmunk has stripes on its face. If there are no stripes, it is a golden-mantled ground squirrel. It can also be identified by its rapid, nervous movements. They have large fur-lined cheek pouches that they use for carrying nuts and seeds.

This species of chipmunk has the largest range of habitat, living from the lowest elevations to timberline and above, primarily in rocky areas.  They burrow beneath rocks, logs, shrubs, and other such shelters.

Least chipmunks are not true hibernators. They are in a state of torpor from which they occasionally arouse to feed on stored food. Breeding takes place shortly after this period, and the gestation period takes four to five weeks. Typically there are five or six young which do not leave the nest until they are about four weeks old. 

Photo courtesy of Dave Herr

Golden-mantled Ground Squirrel

This ground squirrel is often mistaken for a chipmunk because of its resemblance. However it is larger and has no stripes on its head. The tail is also shorter. On its neck and shoulders is a russet to golden “mantle.” Also like the chipmunk, its habitat in Rocky Mountain National Park is from low elevations to well above treeline commonly among rocks near the edge of woodlands. They are quite brazen as they beg for peanuts and morsels from picnickers’ and hikers’ lunches.

By late summer, heavy deposits of fat have been stored on their bodies. With the first snows and cold temperatures they move into hibernation. They breed shortly after the period of hibernation. The gestation takes about four weeks giving birth to five young on the average. The stripes are evident after only about four days.

nps photo

Wyoming Ground Squirrel

The Wyoming ground squirrel is a medium-sized squirrel averaging between 10 and 12 inches in length. It is brownish gray with a belly that is whitish to buff. The lack of stripes on its body distinguishes it from the golden-mantled ground squirrel. It often sits in an alert upright pose. They are usually found in relatively open country where the soil is well drained so that there burrows remain dry. They often leave piles of debris downslope from their burrows. This also distinguishes them from the golden-mantled ground squirrel which does not leave such piles. They may range between 6,000 and 12,000 feet. In addition to their favored diet of foliage, they may feed on remains of other ground squirrels particularly those along roads and highways.

During mid-summer their food will begin to be converted to fat to sustain them through their period of hibernation. This begins when they have reached a critical amount of fat regardless of external environmental conditions. Usually this occurs in late August of early September.

Soon after hibernation, these ground squirrels breed. The gestation period is a little over four weeks with a brood of five to six on the average. They are weaned by five weeks and then appear above ground by early June.

nps photo

Chickaree

The pine squirrel or chickaree is the smallest tree squirrel with an average length of 12 to 13 ½ inches. Its coloration is rust red to grayish red, and its tail is outlined with a broad black band edged with white. It is an extremely vocal squirrel, chattering, stomping its feet, and scolding to get the visitor to leave.

It lives mostly in forests at middle elevations. It favors the spruce-fir, Douglas-fir, or lodgepole pine areas to that of the ponderosa pines. It requires cones for food and prefers damp and cool areas for its storage of the pine cones. The chickarees are very territorial and may defend the area by physical combat. They leave piles of litter which can reach ten yards across and 32 yards deep. Cones are stashed in this debris. Chickarees are active during the day and then retire to their nests at night time. Nests may be on the ground or in the crotch of trees or in hollow trees.

Chickarees mate in April usually. The gestation period is about 40 days and usually one to six young are born. They do not leave the nest until they are about 1/3 grown.

nps photo

Abert’s Squirrel

The most distinctive of the squirrels is the Abert’s squirrel with its conspicuous ear tufts and long, full tail. They are fairly large and heavy-bodied getting up to 23 inches in length. The majority of the individuals in the park are dark gray to black.

It is found principally on the eastern edge of Rocky Mountain National Park at elevations of approximately 8500 feet. It prefers ponderosa pine woodlands, but its population is sporadic. It feeds on the ponderosa pine cones but does not store them in appreciable amounts. It builds elaborate year-round nests in ponderosa pine trees. They are active during the day and return to their nests during the night. Their territories are much larger than that of other squirrels.

During the mating season of March to April, females may entice several males to conduct elaborate chases before choosing a mate. Litters of two to five young are born after a gestations period of about seven weeks. They are not weaned until almost 19 weeks in age.