Squirrels are familiar sights in many environments, often observed foraging for food. A common question is their dietary classification: are they herbivores, consuming only plants, or omnivores, with a more varied diet?
Understanding Dietary Classifications
Animals are broadly categorized based on their primary food sources. A herbivore is an animal that exclusively eats plants and plant-based materials for energy and nutrients. Herbivores possess specialized adaptations, such as flat teeth for grinding and complex digestive systems, to process fibrous plant matter efficiently.
An omnivore is an organism capable of feeding on both plant and animal sources. Omnivores derive nutrients from a wide range of materials, which can include fungi, plants, and other animals. Their digestive systems are often adapted to process this varied diet, and they may possess versatile teeth structures, including both flat molars for grinding plants and sharper teeth for tearing animal matter.
The Primary Plant-Based Diet of Squirrels
The vast majority of a squirrel’s diet consists of plant-based materials. Squirrels frequently consume nuts such as acorns, walnuts, pecans, hazelnuts, and hickory nuts. They also readily eat a variety of seeds, including pumpkin seeds and sunflower seeds. Fruits and berries, like apples, grapes, strawberries, blueberries, and raspberries, are significant components of their diet, particularly in summer and fall.
Beyond nuts and fruits, squirrels forage for other plant parts, including leaf buds, tree flowers, and young shoots. Fungi, such as mushrooms and truffles, also contribute to their nutrition. Their physical adaptations support this plant-heavy diet; squirrels possess strong jaws and continuously growing, sharp incisors suited for gnawing through hard shells and fibrous plant materials.
When Squirrels Diversify Their Meals
While plant matter forms the bulk of their diet, squirrels are opportunistic feeders and will diversify their meals with non-plant items, especially when typical food sources are scarce. For instance, squirrels are known to eat insects, including beetles, caterpillars, grasshoppers, crickets, and larvae. These animal additions can provide valuable protein, particularly when plant-based options are limited.
Squirrels have also been observed consuming bird eggs and even young nestlings. Specific species like flying squirrels may exhibit more carnivorous tendencies, eating bird eggs and nestlings. Recent studies have documented California ground squirrels actively hunting and consuming small mammals like voles, particularly when vole populations are high. This dietary flexibility, though not their primary mode of feeding, clarifies why squirrels are best classified as omnivores, rather than strict herbivores.