James Taulman is a semi-retired wildlife biologist who travels observing wildlife in New Mexico and the southwest.
Also called the tassel-eared squirrel, this tree squirrel inhabits cool, dry ponderosa pine forests from New Mexico up through the Rocky mountains of Colorado and the Colorado Plateau, Utah, and northern Arizona. There are four separate populations of Abert’s squirrels across their range, all occurring in areas where Ponderosa Pine forests are present. This is one of three tree squirrels in Colorado, the other two being the Red squirrel and the Fox squirrel. The Abert’s squirrel may be identified by several features. First, its habitat is distinctive, being mature Ponderosa pine forests, which proliferate at elevations between 6000 and 8500 feet, often with Gambel oak, juniper and other understory hardwood species. It is a rather large squirrel, with a snout to vent length of 18-22 inches and a tail about 10 inches long. Both sexes have light to dark grizzled gray or black bodies with generally a white belly fur and bright white tail under surfaces. The race found on the eastern slope of the Rocky Mountains may be completely black. They have large ears with tufts of hair making the ears appear even larger. They also often show an orange fur patch on the back.
These squirrels eat a variety of plant foods, preferring pine seeds, but they don’t store food in caches like other tree squirrels. They are active during daylight hours year round, consuming the seeds from as many as 75 pine cones per day during the peak cone season from June to October. They also eat the male pollen cones. From December to May the squirrels’ diet heavily favors the tender inner bark of twigs and over the summer fungi and terminal buds are taken. Some carrion also supplements the diet. Like other tree squirrels, they will gnaw on bones and antlers, presumably obtaining needed calcium in that manner. They obtain water primarily from food items, but may also drink from standing water. The home range is widely variable, as in all tree squirrels, depending upon the distribution of required habitat resources like food and forest structure. But in normal conditions males will range within an area of 10-24 acres and females generally show a stronger attraction to a home base (philopatry) with a more limited range of activity.
Females build a spherical nest high in the forest canopy out on the branch of a pine tree, and after the spring mating season produce 2-5 offspring about the first week of June. The young are born naked and helpless (the altricial pattern), and after 6 weeks are fully furred and the eyes are open. By the seventh week they explore around the nest and by the 9 week they venture out and will reach the ground. The young are weaned by the 10th week and reach full size by the 4th month of age. While the age of sexual maturity is not known precisely, it is estimated that Abert’s squirrels are able to breed at about 12 months after birth. Natal nests are also used throughout the year as shelter during harsh weather and for rest periods.
The five most significant mortality factors affecting Abert’s squirrels are, in order of importance: 1) habitat destruction from logging of Ponderosa pine forests and the subsequent reduction in food and refuge resources, 2) the reduction in food availability due to winter snow cover, 3) predation, particularly by forest hawks, like the Northern goshawk, 4) sport hunting, and 5) vehicle collisions. Other natural predators besides raptors, such as bobcats, foxes and coyotes may also take some as they forage on the ground. The squirrels are very fast runners and climbers and the young and older adults are the most vulnerable to mammal predators. Normal life span in the wild is not documented but probably is in the range of 7-9 years.
The International Union for the Conservation of Nature considers the population of the Abert’s squirrel to be stable and of “Least Concern” for conservation.
Photos taken using the Nikon P900 camera. Most information in this summary was taken from: “The Abert’s squirrel (Sciurus aberti): A technical conservation assessment, by James O. Keith, Wildlife Ecologist, Prepared for the USDA Forest Service, Rocky Mountain Region, Species Conservation Project, 2003.”
