Red squirrels (North American and Eurasian species) are small, energetic inhabitants of forested environments whose survival depends on a highly flexible and specialized diet. Their ability to remain active year-round, even in harsh boreal and temperate climates, is linked to an opportunistic feeding strategy that shifts rapidly with the seasons. This adaptability allows them to exploit whatever resources are most abundant in their territory, ensuring a consistent energy supply. Their preference for coniferous forests provides a consistent, high-energy food source that supports their year-round activity.
Primary Fuel: Conifer Seeds and Nuts
The primary caloric intake for most red squirrels comes from the small, energy-rich seeds found within conifer cones, such as those of pines, spruces, and firs. Squirrels exhibit selective foraging behavior, often harvesting cones from tree species that yield the highest seed energy per cone first. To access the seeds, a squirrel employs a distinctive technique, often described as eating “corn-on-the-cob,” meticulously stripping the cone scales from the base upward while twirling the cone in its paws. This action leaves behind a characteristic central core and a pile of discarded scales, which serves as a clear sign of their feeding activity.
In mixed or deciduous forests, hard nuts become a highly prized, energy-dense secondary staple. American red squirrels, for example, will readily select black walnuts over pine seeds when given the choice; populations in these areas have developed larger skulls to manage the tougher shells. The squirrels open nuts, such as walnuts or hazelnuts, by gnawing large, jagged holes from both ends to extract the kernel inside. These seeds and nuts are crucial for building the body mass necessary to endure the colder months, as red squirrels do not hibernate.
Seasonal Plant Foods and Buds
While conifer seeds form the bulk of the diet, the red squirrel’s menu expands significantly during periods when the seed crop is not yet mature or is depleted. In early spring, when other foods are scarce, the diet shifts to include soft vegetative matter like tree buds, flowers, and new shoots. They consume the terminal buds of conifers and the catkins of trees like poplar and willow, providing much-needed nutrients as winter stores dwindle.
Later in the year, particularly summer and autumn, the species supplements its diet with fresh fruits and berries, including species like bearberry. They also occasionally consume tree bark, scraping away the outer layers to reach the cambial tissue and phloem beneath, which offers moisture and carbohydrates. Red squirrels have even been observed “tapping” sugar maples by chewing holes in the bark, returning later to lap up the concentrated tree sap.
Fungi, Insects, and Other Protein Sources
Fungi are a significant component of the red squirrel’s diet, sometimes accounting for up to 80% of their food items in the autumn. They consume numerous species, including subterranean varieties like false truffles (Elaphomyces and Rhizopogon) and cap mushrooms like Boletus. Squirrels often bite off mushrooms and hang them on tree branches to dry, preserving them for later consumption during the winter months.
Red squirrels readily incorporate animal matter into their diet when protein is required or when plant food is limited. This includes consuming insects, insect larvae, and sometimes the eggs or nestlings of songbirds. In certain environments, they have even been known to prey on small mammals, such as young snowshoe hares. Additionally, squirrels chew on discarded bones and deer antlers, which provides a valuable source of calcium and other minerals often deficient in a seed-based diet.
Storing the Feast: Midden Behavior
Red squirrels rely on specialized food storage behavior, known as larder hoarding, which results in the creation of a midden. A midden is a large, centralized cache of cones and cone scales, often located at the base of a tree, under a log, or in a damp, shaded area. This location is chosen because the cool, moist conditions prevent the cones from drying out and prematurely opening, which would cause the seeds to scatter.
In the fall, a single squirrel may harvest and store over 15,000 green cones into its midden, providing a food supply that can last for one to two seasons. These large, resource-rich caches are rigorously defended by the resident squirrel, whose aggressive territoriality is focused on protecting its winter supply. Middens are often reused across multiple generations of squirrels, becoming substantial piles of debris that can measure several feet wide and deep.