Summit Outside: The noisy pine squirrel
I was on my cross-country skis enjoying the peaceful woodland setting, and the quiet was suddenly broken by a loud “chit-chit-chit.” I looked up into the branches of a nearby pine and saw a chickaree. No, a chickaree doesn’t have feathers: It has fur and it was sitting on a branch fussing away. It was a pine squirrel also called a red squirrel, boomer or chickaree. Like the chickadee, the names denotes its vocal propensity. This little, very territorial pine squirrel will loudly scold anyone or anything that comes near its territory. How does such a little critter make such a loud noise? It’s only 14 inches long and weighs only about 9 ounces. The little chatter boxes have a routine call they repeat every minute or so, and they also have a chattering alarm which can be heard up to a quarter of a mile away.
The pine squirrel gray/brown to rusty red fur on their backs with pale orange chests and brownish legs and feet, but in the winter the fur on their backs turns browner and their under parts turn whitish to gray. The eyes have a conspicuous white eye ring, its tail is frosted with buff or white, and ear tufts are more conspicuous in the winter. Pine squirrels are found in mature pine, fir, spruce and mixed-wood forests in Colorado. They depend on trees for food and nests and are found in forests where trees produce quality tree seeds and provide shaded environments that facilitate foraging, maintain appropriate microclimates for middens, and provide cover from predators.
Middens are caches or larder hoards of food mixed in debris from previous year’s cones. (This term is used by anthropologists to look at refuge piles of early man to determine their life styles.) The pine squirrel also hoards large quantities of food in burrows in the ground, neighboring trees and in their nests. Their winter stores sometimes contain more than 150 pine cones! They also eat variety of tree tissues, including buds, flowers, fruits, sap, bark and fungi-like mushrooms. Animal foods are also consumed opportunistically, and these include insects, bones and antlers.
Pine squirrels are active during the day particularly at dawn and in late afternoon, and sleep at night. They nests are in tree cavities or in water-proof leaf nests high up in the trees, sometimes as high as 60 feet. Nest site selection is important for keeping warm, cone and fungal storage, and predator avoidance. Inactive periods are spent in nests or in subnivean tunnels. Subnivean means the space formed when latent heat from the ground melts a thin layer of snow. Subnivean animals move under the snow for protection from heat loss and from predators, and these tunnels are generally maintained at 32 degrees F no matter what the temperature is above the snow. On those really cold, windy days we are unlikely to be chattered at, because the little squirrels are scurrying around in their tunnels under the snow keeping warm. Pine squirrels do not hibernate; they remain active throughout the winter although activity is reduced, and short periods of torpor are known to occur. During prolonged periods of snow cover and cold, pine squirrels can spend the vast majority of their active periods in the subnivean environment.
Individuals live solitarily and vigorously defend territories. Mating occurs during a female’s single day of estrus. Numerous males congregate around the receptive female and compete vigorously for the female. Females may mate with more than one one male. Tree squirrels have two litters of two to five young, one litter in spring, the other in early summer. Males depart after mating and females have sole responsibility for raising the young. Gestation is about seven weeks, and babies are weaned by about eight weeks of age. The vast majority of young leave their nest territory, however many settle within half a mile. Squirrel populations are closely associated with cone crops of coniferous trees and related to food availability.
Pine squirrels are prey for weasels, ermine, fishers, martens, red fox, lynx and bobcat. Significant avian predators include owls and hawks. In some cases, predators can hear the squirrels running about in subnivean tunnels.
Pine squirrels or chickarees may serve as a keystone species in forests due to their larder hoarding behavior. Middens serve as storage areas of tree seed through the stored cones, and provide nutrient in the form of decaying matter (compost), and serve also to distribute pine seeds around their territory. They are actually believed to have influenced the evolution of pine-dominated forests in North America. They have not appeared to have disappeared from areas with high levels of insect infestation and tree mortality, as is occurring locally with the lodgepole pine. The pine beetle may actually serve as a food source for pine squirrels. Have new respect for this chatty, cute, little squirrel next time you hear one, although the noise can be somewhat grating!
Breckenridge resident Dr. Joanne Stolen is retired from teaching microbiology
Rutgers University, and has taught classes at CMC. She is now pursuing a career in art, specializing in nature and many of the animals she writes about. Her work can be seen locally.
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