The Eastern Gray Squirrel (Sciurus carolinensis) is an adaptable, opportunistic omnivore whose diet reflects its environment and the seasons. It thrives in various habitats, from dense forests to urban parks. The gray squirrel is a dedicated scatter-hoarder, burying thousands of food items across its territory to ensure survival during leaner months. This behavior results in a diverse and constantly changing diet tied to the availability of natural food sources.
Primary Foraged Foods
The foundation of the gray squirrel’s diet is the hard mast produced by deciduous trees—fatty, high-calorie nuts and seeds that sustain the animal through winter. Acorns are the most important single food source, alongside black walnuts, hickory nuts, and beechnuts. These lipid-rich foods are stored in great quantities during the fall to build energy reserves for when fresh forage is unavailable.
The squirrel’s caching strategy is nuanced, particularly regarding acorns. White oak acorns, which are sweeter and lower in tannins, germinate rapidly and are generally eaten immediately upon collection. Red oak acorns contain higher levels of bitter tannins and exhibit delayed germination, making them the preferred choice for long-term scatter-hoarding and winter storage. If burying a quick-sprouting white oak acorn, the squirrel often excises the embryo first to prevent germination and spoilage in the cache.
Hickory nuts are also a favored food, supplying a significant percentage of the squirrel’s annual diet. Gathering and caching these hard-shelled items is a major activity, consuming up to 90% of the animal’s time outside its nest (drey) during the peak autumn season. Pine seeds and other mast-bearing gymnosperms supplement this primary diet, though hardwood nuts remain the staple.
Seasonal Foraging and Nutritional Supplements
When the autumn mast crop is depleted, the gray squirrel shifts its focus to other plant materials, which are important during late winter and early spring. They rely on readily available items like tree buds, bark, and flowers. Squirrels gnaw on the bark and cambial tissue of trees, such as maple and yellow-poplar, to access sugary sap and nutrients stored beneath the surface.
The squirrel’s omnivorous nature becomes apparent when primary food sources are scarce. They actively seek out various forest fungi, including mushrooms and truffles, which provide minerals and nitrogen. By consuming truffles, which grow underground, squirrels aid in the dispersal of fungal spores, playing a role in forest ecology.
Protein is obtained through animal matter, which is important for pregnant or nursing females needing additional nutrients for reproduction. Gray squirrels prey on insects, such as caterpillars and beetles, and consume bird eggs and small nestlings. They also gnaw on discarded bones or antlers to acquire minerals like calcium.
Urban Dining and Human Food Sources
In urban and suburban environments, gray squirrels adapt their foraging to include human-supplied food sources. Bird feeders are a common target, offering easy access to high-energy items like sunflower seeds, cracked corn, and suet. This reliable food supply allows urban squirrel populations to thrive at higher densities than their forest counterparts.
Gardens and cultivated areas also become part of the squirrel’s foraging range. They consume cultivated fruits and vegetables, including tomatoes and corn, and will dig up flower bulbs, particularly during the spring. This opportunistic behavior is a significant point of conflict with homeowners.
Scavenging from human refuse, such as trash bins and compost piles, introduces the animals to processed food waste. While they consume items like bread and starchy foods, these often contain high levels of sugar, salt, and fat. Dependency on these low-nutrient, high-calorie foods can lead to health issues and a loss of natural foraging skills, underscoring the risks associated with human interference.