Gray squirrels are one of the most familiar creatures in North America, commonly seen even in major urban areas. Most of the time humans see them, grey squirrels are foraging for food--and keeping a sharp eye out for their many predators, which hunt them on land, in the trees and from the air.
Eastern grey squirrels are very common arboreal, or tree-climbing, rodents across much of North America, including areas well outside their native range. The more elusive western grey squirrel of the West Coast, beset by competition from introduced fox squirrels and eastern grey squirrels, is not flourishing. The versatile greys inhabit many ecosystems, from far-flung Appalachian forests to parks and green spaces in the biggest cities.
Most of the grey squirrel’s diet consists of plant foods. A favourite of eastern grey squirrels are the seeds and nuts of trees such as oaks, hickories, beech and chestnuts. Squirrels also ingest the flowers and buds of such species. Indeed, their hoarding and caching of mast (tree seeds) influences the reproduction and distribution of the trees in question, as obviously not all of the nuts they store away will be eaten. Bark, fungi (which are not plants) and cultivated vegetables like corn are other foods. In their conifer-heavy range, western grey squirrels consume the seeds of firs, pine, spruces and Douglas-fir.
Gray squirrels do not shun a minority of animal prey, either. Some, especially young squirrels, will feast on insects. In "American Wildlife & Plants: A Guide to Wildlife Food Habits," Martin et al. note that bits of weevil identified in grey-squirrel stomachs are probably the result of accidental swallowing while the rodents are eating acorns; the authors do observe, however, that other insect foods, from ants to cocoons, are eaten with some regularity. Gray squirrels sometimes consume the eggs and nestlings of birds, as well. Oregon State University notes that western grey squirrel consumption of aphids may help the Oregon ashes that the insects infest.
Small and common, grey squirrels face a huge variety of predators in American forests. Birds of prey are important threats; among the most committed of avian squirrel-hunters are great horned owls, which dispatch the squirrels under cover of darkness, and forest-dwelling hawks like red-shouldered and Cooper’s hawks. Mammalian hunters include a number of members of the weasel family, including the arboreal pine marten and fisher, as well as foxes, bobcats and Canada lynx. A species account for the eastern grey squirrel by the American Society of Mammalogists notes such cold-blooded predators as rattlesnakes and even largemouth bass.
Gray squirrels have long interacted with humans on a food-web level. Besides raiding agricultural plots on occasion, squirrels are hunted for consumption and sport. The University of Michigan Museum of Zoology’s Animal Diversity Website suggests a significant economic value from squirrel hunting in the state of Mississippi on the order of £8.1 million.