Squirrels

Excuse me!  Your bird feeder is empty!  That’s what the squirrels in my backyard tell me every other day.  I have several feeders, some year round, and more in the winter months.  Squirrels are alert, always wary of their surroundings, yet show very little fear of humans  They are presumptuous, eager, intelligent, and fun to observe.  Unique adaptations allow some to scurry up and down tree trunks, and others to fly. 

Eastern Grey Squirrels, Sciurus carolinensis, seem to be everywhere, running up and down tree trunks, scampering across limbs, leaping from tree to tree, and planning new ways to get into the neighborhood bird feeders.  They are active year-round and are diurnal, active early in the morning and late in the afternoon, often resting during the middle of the day, but, even while resting, they must be constantly alert for predators.  Squirrels are shades of black and brown fur tipped with gray above with white bellies.  When looking up into the trees, the lighter colored underside blends with the sky making it harder to see.  For a predator flying overhead, the darker shades of the squirrel’s back blends in with the leaves, twigs and ground colors.  At this time of year, activity increases as squirrels cut, drop and bury nuts for the winter.  Each nut is buried separately under one to two inches of soil.  Squirrels do not have to remember where they buried their food because of their excellent sense of smell.  They can detect a buried nut from up to a foot away even through layers of soil.  Grey squirrels will find and eat about 85% of their cached food each season.

The Eastern Fox Squirrel, Sciurus niger, is the largest squirrel in northern Illinois.  It is similar in coloration to the Grey Squirrel, but with yellow undersides and no silver tipped hairs on its back.  Although not considered a social species, several individuals may den together in the winter to maintain warmth.  Fox Squirrels prefer winter dens in holes in trees, often using abandoned woodpecker holes.  If there are no holes available, they will build a leaf nest with a side entrance hole and line it with grass, leaves, and moss.  They also cache nuts for the winter, using tree cavities whenever possible.  Fox Squirrels may have four to six active dens at any time, switching between them.

The Red Squirrel, Tamiasciurus hudsonicus,  sometimes known as Pine Squirrel or Chickaree, is our smallest squirrel, not often seen in DuPage County, which is on the southern edge of its range.  Red Squirrels have rust-red to grey coats, brightest on their sides with white bellies.  In winter, a black line separates the red from white on the body and carries through the tail with the black band edged in white.  They are the most carnivorous of the species inhabiting this area  bird eggs and young birds in addition to nuts, berries, and seeds.  They cache pine cones for the winter.  Red Squirrels also feed on sugar maple and red maple trees, chewing into the xylem under the bark to start a slow flow of sap.  As the mixture of glucose and water oozes out, the squirrel will leave the patch to dry.  As it leaves the tree, wet sap is about 2% sugar.  As the water evaporates, the remaining mixture becomes almost 55% sugar, a high energy food.

The last of our acrobats, the Southern Flying Squirrel, Glaucomys volans, has a silky coat, brown on the back and white on the belly, with an extra fold of skin between the forelegs and the hindlegs.  This skin allows Flying Squirrels to glide from a high trunk to a lower one, traveling up to 80 yards in one leap.  Their wide, flat tails are used as rudders to turn or change the angle of descent in mid-air.  The tail also acts as an air brake, dropping to slow their descent as the forelegs are raised and the squirrel makes a soft landing.  Although active only at night, they immediately move to the other side of the trunk on landing in case there are any predators – owls – following their flight through the trees.  Flying Squirrels are agile climbers and gliders, but are clumsy on the ground, so they spend a majority of their time among the trees.  They prefer to live in large, mature forested areas where trees are spaced far enough apart to allow gliding without obstacles.  Preferred foods include nuts, berries, seeds and bird eggs.  These ravenous squirrels may store as many as 15,000 nuts in one season.

All squirrels move easily through the trees.  They have sharp claws for climbing and hanging onto vertical tree trunks.  Muscular legs allow them to jump between branches and from tree to tree.  In winter, feet and toes are covered with hair for extra grip on slippery surfaces.  Squirrels can go down a tree trunk head first, just as fast as they can go up, due to a unique adaptation that allows these animals to turn their paws 180˚ and provide just as much grip in either direction.  When observing squirrels, note their tail movements.  Tails are used for balance and communication, flicking movement indicates agitation from danger close by, and the faster the flick, the more dangerous the situation.  Squirrels also use calls to communicate.  A rapid kuk-kuk-kuk indicates immediate danger.  As the danger passes, the call will slow down.  Once the danger is gone, calls will stop and tails will be laid comfortably along backs.

Oak-hickory forests cover one fourth of all the forested areas east of the Mississippi River in the United States.  Winds carry some seeds long distances, others encased in tasty fruits, will be eaten and dropped far from the plant they grew on.  Acorns and nuts are relatively heavy, falling to the ground immediately underneath the parent trees.  Squirrels and oaks have a wonderful relationship, where one gets food and shelter, and the other gets its offspring spread across the forest.

As forested areas are overtaken by human development, they are cut up into smaller and smaller islands of habitat.  Many squirrels are well adapted to live in urban environments among humans and our dwellings.  They can easily switch to different food groups including berries, seeds, fruit, mushrooms and nuts.  All of these are plentiful in our gardens and bird feeders.  An urban environment can support up to 20 squirrels per acre compared to a forested acre that supports only one to two individuals due to competition for food.  Squirrels provide many ecological services from reforestation to providing a source of food for predators, as well as endless entertainment for us!