By Tina Mitchell
It’s 8 a.m. at the wildlife rehabilitation center where I occasionally volunteer, and the place already bustles with activity. This particular morning, we have 66 orphaned or abandoned baby squirrels to weigh, 66 formulas to blend, 66 babies to hand-feed, 66 babies to clean up and settle back into their cages – all before 11 a.m., when the next round of feedings begins. After a quiet winter at the rehab center, everything kicks into gear with the beginning of breeding season – and the squirrels typically lead that parade. Indeed, in early February I spotted several Fox Squirrels engaged in courtship behavior: chasing, spiraling and chattering around a tree trunk, across the ground, and up another trunk. This can only mean one thing – the spring baby squirrel season arrives this month.
Few wild mammals share as close an association with us as these rodents do. Yes, that’s right – rodents. Squirrels belong to an order of mammals called Rodentia, the largest and most diverse group of mammals on the planet. More specifically, the Sciuridae (squirrel) family includes marmots, prairie dogs, chipmunks, ground squirrels and tree squirrels.
If you’ve been to the tropics, you probably noticed that the treetops there host a variety of mammals – monkeys, tree shrews and many groups of rodents, in addition to a tremendous diversity of tree squirrels. But in the cooler temperate forests of North America, tree squirrels alone rule the forest canopies and urban treescapes. Three species of tree squirrel call Colorado home. The black, tassel-eared Abert’s Squirrel depends on ponderosa pines from 7,000 to 8,500 feet in altitude. The diminutive Pine Squirrel populates pine and spruce forests at altitudes ranging from 6,000 – 12,000 feet. Introduced from its eastern range into western towns and cities, the non-native Fox Squirrel has adapted extremely well, spreading and thriving in woodlands and urban areas alike.
Tree squirrels have two breeding seasons: one in the spring, and one in the fall. Since tree squirrels don’t hibernate, the end of winter is a tough time. Food caches of seeds and nuts, which squirrels rely on to get through the winter, have been depleted. Spring brings a flush of new growth, but these buds, catkins and softer bark don’t offer much nutrition. As a result, spring litters tend to be small. Not all females breed in the spring and those that do have only two or three babies. But come late summer – with its ample supply of seeds, nuts, acorns, fruits, berries, pine cones and other nutritious goodies – stand back! Baby squirrels abound in the fall, with litters for some species numbering as many as five or six young.
Tree squirrels exhibit several interesting physical characteristics. Have you ever suffered a squirrel’s gnawing a wooden bird feeder or your wood siding? As with all rodents, its teeth grow continually throughout its life, up to six inches a year. (In fact, the word “rodent” derives from the Latin rodere, meaning “to gnaw.”) It has to chew constantly to both wear down and hone its front teeth into sharp little chisels. Ever seen a squirrel with its tail draped over its back? That bushy tail provides cooling and shade (as well as helping with balance and communicating with other squirrels). In fact, the family name Sciuridae means “shade tail.” Notice how differently a cat and a squirrel navigate a tree. Both can race straight up a trunk, but a cat has to carefully back down the trunk. A squirrel, though, can zoom headfirst down the trunk because its hind feet actually rotate 180 degrees, letting it easily hang upside down as it digs in with its sharp, curved claws.
While tree squirrels often offer a source of engaging entertainment, they – especially urban Fox Squirrels – can also act like hooligans as they destroy gardens, empty bird feeders, steal eggs and nestlings from bird nests, strip bark from trees, and damage all sorts of wooden structures. Some people who really dislike squirrels wonder why wildlife rehabilitators even bother to hand-raise and release these abundant rapscallions. Yet even if you don’t like squirrels themselves, you probably like, or at least appreciate, some of the many creatures that eat squirrels. Eagles, hawks, coyotes, bobcats, foxes – all relish “squirrel” on the menu. From plankton and vegetation to the largest meat-eaters, nature’s food chain depends on all of its links, even if that particular link may be wreaking havoc in your neighborhood.
Tina Mitchell watches nature with her human and canine family from their perch in the piñon/juniper habitat of western Fremont County. When she needs to pay the bills, she shows up as a research psychologist on the University of Colorado Anschutz Medical Campus in Aurora.
