The typical image of a squirrel involves a bushy-tailed animal burying acorns or cracking open nuts. This common perception correctly places the Sciuridae family (tree squirrels, ground squirrels, and chipmunks) as primarily herbivorous. However, the reality of their diet is far more complex and adaptable than simply consuming seeds and plant matter. The quest for survival and specific nutrients can lead these familiar rodents to expand their menu.
The Standard Squirrel Diet
A squirrel’s diet is overwhelmingly composed of plant-based foods, supporting their high-energy, active lifestyle. Foraging focuses on readily available items like nuts, seeds, and fruits, which provide the bulk of their calories. They also consume fungi, tree buds, flowers, and the inner bark or sap from certain trees.
Caching is a defining characteristic of their feeding strategy, involving the storage of food for later retrieval. Tree squirrels, such as the Eastern Gray Squirrel, primarily engage in scatter-hoarding, burying individual nuts across a wide area. This behavior ensures survival during periods when food is scarce, such as hard winters or late spring before new growth appears.
Are Squirrels Omnivores?
Despite their preference for plant matter, squirrels are accurately classified as opportunistic omnivores, consuming both plant and animal material when the chance arises. This behavior confirms they eat rodents, as vulnerable young mice, voles, or small rats can become a food source. While not predators like a fox, they readily exploit prey they can overpower or find defenseless.
The animal matter consumed regularly includes insects, caterpillars, and other arthropods. Squirrels are also known to raid bird nests to eat eggs and nestlings, which provides a high-protein meal. The consumption of small, vulnerable mammals, especially baby rodents found near burrows, is a documented reality of their flexible diet.
Nutritional Drivers for Meat Consumption
The motivation for consuming animal protein and small rodents is rooted in the need for calcium. A diet composed almost exclusively of seeds and nuts, while calorie-dense, often has a poor calcium-to-phosphorus ratio. High phosphorus combined with low calcium can inhibit absorption, potentially leading to Metabolic Bone Disease (MBD).
Calcium is necessary during high-demand periods like gestation and lactation, when females require significant amounts of the mineral. Consuming animal tissue, eggs, or gnawing on bones and shed antlers is an instinctive mechanism to supplement this deficiency. This behavior ensures they maintain strong bone density and proper bodily function.
The protein in animal sources also offers a more complete amino acid profile than plant matter alone. This protein boost is valuable for growth, muscle repair, and overall health, especially for juveniles and breeding adults. Actively preying on a small rodent provides a complete source of high-quality protein and bone-building calcium.
Variations Across Squirrel Species and Environments
The extent of omnivorous behavior differs significantly depending on the species and environment. Tree squirrels, like the Eastern Gray Squirrel, typically limit animal consumption to opportunistic finds, such as insects or bird nest contents. Their forest canopy environment makes encounters with terrestrial rodents less frequent.
Ground squirrels, however, often exhibit more pronounced predatory tendencies. The California Ground Squirrel (Otospermophilus beecheyi), for example, has been observed actively hunting and killing California voles (Microtus californicus). This behavior is often triggered by environmental conditions, such as a high density of voles or a temporary scarcity of preferred plant-based foods.
This active hunting demonstrates behavioral flexibility that allows certain squirrel species to maximize available resources. When small rodents are abundant, squirrels adapt their foraging strategy to take advantage of the dense, readily available protein and calcium source.