What's a Drey? A Peek into the Lives of Squirrels at Wellesley

Gray squirrels (Sciurus carolinensis) may be the most commonly recognized mammal on campus, skittering about snacking on fallen acorns or sheepishly nibbling an occasional tortilla chip or other human-derived treat. They seem to operate in a world of their own—while aware of surrounding humans, they are always busy as they scramble around, deftly moving from ground level to the tops of large trees. Their acrobatic movements in treetops impress onlookers, as they sometimes seem to barely avoid falling. Campus squirrels are so amusing and charismatic that they have inspired several instagram accounts including @wellesleycollegeboyz and @squirwelles.

Squirrel, recently spotted on iNaturalist, eating a tortilla chip found in nearby trashcan by the Lulu Chow Wang Campus Center.

But where do the squirrels go during frigid winter days like today, or during the night? Squirrels don’t hibernate, and can be seen foraging for seeds, berries, and nuts throughout the winter, but they do need refuge at night and when the weather gets particularly cold.

With Fall comes leaf senescence: leaves fall off trees, bringing to view the gray squirrel’s home: the drey, a large and cozy nest constructed in the crook of a branch at least 20 feet from the ground. Dreys look like a large haphazard sphere of leaves and sticks, yet they are in fact very complex, having central cavities of about 6-8 inches across to allow space for the squirrel. Rugged outer walls are lined with an inner layer of finer materials like pine needles and moss.

A squirrel drey by Simpson Hall.

To get ready for the winter’s bitter cold, squirrels begin to build and bolster their dreys in the summer or early fall, starting by gnawing small live branches, with leaves attached, off trees. Gathering the sticks before leaves begin to fall is key—the leaves simply dry on the sticks without falling, remaining intact to function as natural insulation for the squirrel’s winter refuge.

Many squirrels choose to make not just one drey, but two! They’ll use the second as a backup home, just in case their first is disturbed by a predator or parasites. It’s no wonder squirrels seem so busy. All the while, they are busy gathering mast—nuts like acorns and beechnuts—in large communal buried stores, which will help them survive the harsh winter.

Next time you go for a walk on campus, or even are simply walking from East Side to West Side, try to count how many dreys you spot. You might be surprised by just how many you see!