The common perception of the squirrel as a small animal whose diet consists almost entirely of buried acorns and scavenged sunflower seeds is widespread. These familiar backyard rodents are indeed masters of foraging for plant matter, but their true dietary habits are far more flexible than their reputation suggests.
The Core Answer: Squirrels as Opportunistic Omnivores
The most accurate classification for many common squirrel species, including tree squirrels and ground squirrels, is opportunistic omnivore. While vegetation forms the largest part of their caloric intake, they readily consume animal matter when the opportunity arises or when their nutritional requirements change.
Squirrels require foods rich in protein, carbohydrates, and fats because they are unable to digest cellulose, the structural component of many plants. This need for concentrated nutrition means they will seek out animal-based sources when high-quality plant food is scarce.
Defining the Primary Diet: The Standard Menu
The foundation of a squirrel’s diet is firmly rooted in plant matter, providing the bulk of their energy and fat reserves. These animals consume a wide array of nuts, seeds, and fruits, which offer the high-fat and high-carbohydrate content they need. Acorns, walnuts, pecans, and pine nuts are frequently targeted for their caloric density and are often cached for later consumption.
Beyond nuts, squirrels consume fungi, tree buds, and the tender cambium layer of tree bark, especially during winter. They also eat various forms of green vegetation, including flowers and roots, when foraging on the ground.
The Protein Sources: What “Meat” Means to a Squirrel
When seeking protein, squirrels consume animal matter that is often lacking in their primary plant diet. Insects are a common and consistent component of their food intake. They readily consume grasshoppers, caterpillars, beetles, and grubs.
Squirrels are also known to raid bird nests, consuming eggs and nestlings. This behavior is driven by the high concentration of protein, which is beneficial for lactating females or during periods of rapid growth. They also consume small vertebrates, such as young snakes, lizards, and even mice.
Some species, like the California ground squirrel, are not merely scavengers but active hunters. Researchers have observed these ground squirrels pursuing, killing, and consuming voles, demonstrating flexible predatory behavior.