squirrel on decka grey squirrel on our deck

February 19, 2019

You may think it is still the dead of winter, but some members of our wildlife community are already busy starting their families. Female squirrels are advertising for mates from the treetops, using duck-like “come hither” calls, and interested males have responded by racing through the branches after them.  After a female relents and accepts a suitor, she prepares a warm sheltered nest in a hollow tree if one is available, or builds a leaf nest if no cavity is handy. She generally gives birth to two or three kittens in this first litter, but the second pregnancy that takes place in late spring can often produce up to six young.

Wisconsin is home to ten species of squirrels. Besides the gray and red squirrels, we have the fox squirrel, two species of flying squirrels (Northern and Southern), two species of chipmunk (Eastern and Least), the 13 lined ground squirrel, the Franklin's ground squirrel and the woodchuck. Black squirrels are considered a color variation of the gray squirrel, and all squirrels are members of the rodent family.

Of the tree squirrels, the red is the smallest, only 11 to 14 inches long including a 4- to 6-inch tail. It is reddish to reddish-gray on top with a white or cream underside.  Red squirrels live in coniferous and mixed forests throughout northern Wisconsin where they feed primarily on pine seeds.  The fox squirrel is the largest species and has rusty brown fur with a pale yellow to orange belly. Its diet is made up of nuts, seeds and buds and although it is a tree squirrel, it spends a lot of its time on the ground.

Most commonly seen is the gray squirrel.  This has muscular hind legs that allow it to leap more than 20 feet, and long hind feet that are double-jointed and equipped with sharp claws to help it scramble head first down a tree trunk. If it should fall, it can land safely from heights of 30 feet and more, and we have seen one just drop to the ground rather than bother to climb down. When danger threatens a squirrel will sidle inconspicuously around the trunk of the tree, keeping just out of sight. When it remains motionless against tree bark, it can be very difficult to see.

The most notable physical feature of this squirrel is its large bushy tail. This acts as a rudder when the animal jumps from high places, as a warm covering during the winter, as a counterbalance when walking a telephone wire, as a signal to other squirrels, and as a distraction to a pursuing predator. If necessary, a squirrel can lose much of the skin and even some of the bones of its tail to escape a marauder’s grasp, and it is not uncommon to see one with only a partial tail.

The eastern grey squirrel’s diet varies with the seasons. In early spring, it eats the buds of hardwood trees, especially maple. During the summer, maple and elm seeds are major food items, as well as a wide variety of berries and wild fruits. Squirrels also eat insects, caterpillars, and will happily clean out a nest of birds’ eggs or young birds.  In the autumn, their most important foods are nuts, including acorns, hickory nuts, walnuts, and pine seeds.

The squirrel's front teeth continue to grow throughout life, so they can never be worn away by the animal's gnawing on such hard materials. Squirrels bury hundreds of nuts and seeds for the winter. They will wait out very cold weather in their nests, often with others of their kind for warmth, and then emerge to search for a larder. Contrary to popular myth, squirrels do not find buried nuts by memory but by their highly developed sense of smell. Not all hidden nuts will be found though, and some will germinate and grow into new trees.

Tree cavities, usually those formed by woodpeckers, often serve as nurseries.  If existing trees lack cavities, leaf nests known as dreys are built by cutting twigs and weaving them into warm, waterproof shelters.  The newborn kits are naked and blind but mature quickly and by 12 weeks they will be almost fully grown. An adult grey squirrel grows to about 18 inches in length, half of which is tail. It is usually grizzled salt and pepper with a white belly but can also occur in a black color phase. The average squirrel’s lifespan is normally less than six years, although some have been found to be as old as 13 years in the wild.

I think it somewhat ironic that although these little rodents cause limited damage in America, they were considered a major pest in England and Europe, much as the English sparrow is here. They were introduced there in the late 1800's from North America and their numbers reached the point where strong fears were being expressed for their effects on both the bird population and the general health of the forests. Bird enthusiasts were noting the rapid decline in songbird numbers and blaming it upon squirrel predation of eggs and the young chicks.

In addition, Great Britain’s inoffensive native red squirrel was being squeezed into isolated areas, not because the grey physically attacked the red, but because it competed for the food supply and carried a virus lethal to the reds. This situation seems to be improving with the protection and reintroduction of the pine marten in that country, because in areas where these predators now exist, the grey squirrel numbers are declining to everyone’s relief. 

When I was a youngster, a wild squirrel would come to our Chicago suburban backyard and accept nuts from my brother’s and my fingers, an experience that led to a lifelong passion for the outdoors and its inhabitants.  Fortunately, in our country, eastern grey squirrels are only nuisances when they invade an attic, dig up bulbs in gardens or drive birds away from feeders.  Balancing this is the pleasure they give to numerous city dwellers, campers, and everyone who enjoys the outdoors.  The woods would be a much lonelier place without their hustle and bustle and cheerful chatter.