The Eastern gray squirrel, Sciurus carolinensis, is a highly adaptable rodent recognized across North American forests and urban areas. Its success is tied to its varied and opportunistic feeding strategy, allowing it to thrive in diverse environments. As an omnivore, the gray squirrel consumes a wide array of plant and animal matter, adjusting its intake based on immediate availability and nutritional needs. This flexible approach is fundamental to maintaining the energy reserves required for year-around activity and reproduction.
Primary Energy Sources
The bulk of the gray squirrel’s diet, especially during the autumn, consists of high-calorie, hard mast crops such as nuts and acorns. Their high content of fats and carbohydrates allows the squirrel to build up fat reserves for surviving the winter months. Preferred sources include hickory nuts, walnuts, pecans, and beechnuts, which are richer in lipids and protein compared to acorns.
Acorns, while abundant, are often a secondary preference, especially those from red oaks, which contain higher levels of tannins. Squirrels prefer to consume lower-tannin white oak acorns immediately because they germinate quickly. They often cache the less perishable, higher-tannin red oak acorns for later use. An adult gray squirrel can consume about 80 grams of shelled nuts each day to sustain its high-energy lifestyle.
Seasonal Supplements and Protein
When the hard mast supply is depleted, gray squirrels depend on a wide range of soft mast and seasonal supplements. In the spring, they frequently feed on tree buds, flowers, and the shoots of deciduous trees like maple, tulip poplar, and black cherry. This consumption helps them acquire vitamins and minerals following the winter scarcity.
As omnivores, gray squirrels seek out protein sources to supplement their plant-based diet. They consume insects, including larvae found in goldenrod galls, as well as bird eggs and nestlings when the opportunity arises. This animal matter provides a concentrated source of protein, which is beneficial for lactating females and growing juveniles. Fungi, including various forest mushrooms, are also incorporated into the diet year-round, offering nitrogen and minerals.
Food Acquisition and Storage
The gray squirrel manages its food supply through a behavioral strategy called scatter hoarding. Individual food items are buried in numerous shallow caches across its territory. This prevents the loss of an entire food supply to a single competitor and aids in future forest regeneration when forgotten nuts germinate. To relocate these hidden caches, squirrels utilize a combination of spatial memory and their sense of smell (olfaction).
Licking an acorn before burying it leaves a scent signature that acts as an olfactory signpost, helping the squirrel detect the cache through snow and frost. Beyond food, squirrels seek out mineral supplements to maintain skeletal health and sharpen their incisors. This often involves osteophagy, or the consumption of bone, leading them to gnaw on shed deer antlers or bone fragments found on the forest floor. These bony structures are rich in calcium and phosphorus, which are important for females during pregnancy and lactation.