Red squirrels can be easily distinguished from other North American tree squirrels by their smaller size, 1–14 in total length (including tail), territorial behavior, and reddish fur with a white underbelly. Red squirrels are somewhat larger than chipmunks. American red squirrels are widely distributed across the North American continent and most of Canada. To communicate, an American red squirrel makes a lengthy, descending trill and a chatter of assorted notes and chucks. American red squirrels mainly feed on the seeds and cones of evergreen trees. However, they will also eat bird eggs, berries, and fruit when they are available.

Red squirrels are territorial, and build nests which may be a hole in a tree trunk or a tightly constructed mass of twigs, leaves, mosses, and lichens in the densest foliage of a tree (making the nest almost completely weatherproof). A loose mass of twigs and leafy debris in a high tree is used as a “fair weather” nest. Their ground burrows, also known as middens, are used mostly for food storage. There is usually one large active midden in each territory with perhaps an inactive or auxiliary midden.