The Fox Squirrel (Sciurus niger) is the largest native tree squirrel in North America, known for its highly adaptable, omnivorous diet. This flexibility allows the species to thrive in a wide variety of habitats, from dense forests to suburban parks. The foods it consumes change significantly with the seasons. Understanding the fox squirrel’s diet requires looking at its primary sources of nutrition and the specialized behaviors it uses to find and secure food.
Staple Foods: Nuts, Seeds, and Acorns
The foundation of the fox squirrel’s diet is hard mast, which includes the nuts and large seeds produced by hardwood trees. These items are concentrated sources of fat and protein, making them the most valuable food for sustaining the squirrel through the winter and during reproduction. Preferred mast includes acorns from various oak species, as well as nuts from hickory, pecan, black walnut, and butternut trees.
Fox squirrels often begin consuming these items even before they are fully mature, starting with green acorns and hickory nuts in late summer. They use their continuously growing incisors to gnaw through the tough shells of these nuts, often opening them neatly by prying along the seams. The availability of these high-calorie foods is a primary factor determining the presence and health of fox squirrel populations in a given area.
Seasonal and Supplemental Plant Sources
When the autumn mast crops are depleted, fox squirrels turn to a variety of seasonal and supplemental plant materials. During the spring, the diet shifts dramatically to incorporate soft plant parts, such as elm and maple buds, flowers, and the newly developing seeds of trees like elm and silver maple. These items provide necessary moisture and vitamins that may be scarce during the late winter months.
In the lean period of late winter and early spring, they may strip and consume the inner cambium layer of tree bark, particularly from species like eastern cottonwood. They also consume various fruits and berries throughout the summer and fall, including mulberries, plums, cherries, and blackberries. Fungi, such as mushrooms and truffles, are also incorporated into the diet, serving as a supplementary resource that provides hydration and nutrients.
Non-Vegetarian Food Items
While the fox squirrel’s diet is predominantly plant-based, it is an opportunistic omnivore that consumes animal matter for a boost of protein. This protein intake is particularly important during the spring and summer breeding seasons when the demands of raising young are highest.
Insects are a common non-vegetarian food source, with squirrels eating grubs, beetles, and insect larvae found in the soil and on plants. They also opportunistically prey on the eggs and nestlings of birds, a behavior that provides a concentrated source of fats and protein. Although less common, fox squirrels may also consume small vertebrates or scavenge carrion.
Foraging Behavior and Food Caching
The fox squirrel’s primary foraging strategy involves searching both on the ground and within the tree canopy, particularly during the early morning and late afternoon hours. A highly developed sense of smell is crucial for locating food buried beneath the soil or snow, as well as for assessing the quality of a potential food item. When a squirrel finds a cacheable item, it engages in specialized assessment behaviors, such as “paw manipulation” and “head flicking,” which help it judge the item’s weight and perishability.
The species utilizes a strategy known as scatter hoarding, burying individual nuts and acorns across a wide area for later retrieval. This behavior reduces the risk of having a single food store pilfered by a competitor. Squirrels are more likely to cache items that are less perishable and higher in value, such as hard-shelled walnuts and hickory nuts, over softer, more perishable foods. The practice of burying seeds and nuts far from the parent tree also aids in the dispersal of seeds, making the fox squirrel an important factor in the health and regeneration of forest ecosystems.