On our Arb Walk last Friday, we had the good fortune of a lot of eager visitors, and a blanket of fresh snow. Abbondanza! Because the snow had fallen only earlier that day, most of the tracks we saw were left by a common daytime ground-frequenter: squirrels! Don’t let their familiarity fool you, these are exciting wildlife creatures.
For starters, we have four different species of squirrel in the arb: Gray Squirrels (Sciurus carolinensis), Fox Squirrels (Sciurus niger), American Red Squirrels (Tamiasciurus hudsonicus), and Thirteen-Lined Ground Squirrels (Spermophilus tridecemlineatus). You wont be seeing the Ground Squirrel until March or early April—like other ground squirrels, they’re hibernating. But the other three species of tree dwellers are quite active in the winter months. They keep warm in large nests called dreys constructed in trees (often nut-bearing trees like walnuts and oaks) though they will also make homes in tree hollows as well. Gray Squirrels and Fox Squirrels build similar nests—a large conglomeration of twigs and leaves. Red Squirrels on the other hand will make a cozy nest of woven tree bark, moss, and grass.
The subtle distinctions continue: each species has its own unique way of cracking walnuts, and studying a pile of shells can tell you who’s done the eating. Red Squirrels will neatly break into each separate quadrant of the nut whereas Fox and Gray Squirrels will more or less tear the shell to pieces.
Other squirrel signs: their distinctive box-shaped track (careful! the front feet will be located behind the rear feet in their tracks), bark peelings for nests (red squirrels seems to prefer honeysuckle bark), and chews where squirrels have gnawed on bark to sharpen their teeth. Squirrel chews often look a lot like woodpecker activity, but closer inspection will usually reveal incisor marks in squirrel chews.
Learning about squirrels is useful tool for other naturalist pursuits. For example, squirrels will sound their alarm call if they see a potential predator (coyotes, hawks, etc.) and if you learn what it sounds like, you can use it to know if there is a predator in the area to watch for. Because squirrels are so ubiquitous, you can use this trick almost anywhere to spot coyotes and hawks and the like. So don’t forget squirrels!
Your Student Naturalists are Amy Alstad ’09, Jeremy Hayward ’09, Lindsey Nietmann ’09, David Smith ’09 (off-campus), Hannah Specht ’09, John Vigeland ’09, and Mira Alecci ’11. Please contact any of us (or Arb Director, Nancy Braker) with questions or suggestions!