Common tree squirrels, such as the Eastern gray squirrel and the fox squirrel, are highly adaptable omnivores found across North America. Their diet is diverse and changes constantly, reflecting their need to forage and prepare for seasonal changes. As active, non-hibernating rodents, they require a consistent intake of high-calorie foods to maintain their energetic lifestyle and body temperature. Their survival hinges on their ability to find a variety of plant matter and, to a lesser extent, animal matter to meet their nutritional requirements.
The Primary Natural Diet
The foundation of a squirrel’s long-term diet is hard mast, which includes the large, energy-dense seeds of woody plants. Acorns from oak trees, along with nuts from hickory and walnut trees, are prized for their high caloric content. These foods are consumed immediately in the autumn and are also buried in thousands of separate caches, a behavior known as scatter-hoarding, to serve as the primary fuel source during winter.
Hard mast is supplemented by soft mast, which encompasses berries and wild fruits available in the forest. These softer foods, such as mulberries and wild cherries, provide carbohydrates and moisture, but they cannot be stored long-term. Fungi, including various mushrooms and even underground truffles, also form a regular part of the natural diet. The consumption of fungi provides squirrels with essential nitrogen and minerals like calcium and potassium, which are often less abundant in a purely nut-based diet. The high-fat and high-carbohydrate nature of this diet is necessary for building the fat reserves needed to survive periods of food scarcity.
Seasonal Variation and Opportunistic Sources
A squirrel’s diet shifts considerably as the seasons change and different resources become available. In early spring, when buried caches may be depleted and new nuts have not yet formed, squirrels turn to newly emerging plant material. This includes the carbohydrate-rich buds, flowers, and tender new shoots of trees like maple and elm, which provide a quick source of energy.
The summer months introduce a greater variety of food, including protein-rich animal sources. Squirrels will forage for insects, such as caterpillars, grubs, and insect larvae, to meet their increased protein demands, especially during breeding season. They may also opportunistically consume bird eggs or carrion, demonstrating their omnivorous nature when high-quality protein is scarce.
Squirrels living near human habitation become opportunistic feeders, supplementing their wild diet with easily accessible sources. They frequently raid backyard bird feeders for sunflower seeds and suet, which are high in fat and calories. They also forage in gardens, consuming bulbs, vegetables, and cultivated fruits, highlighting their ability to adapt their foraging strategies to urban and suburban environments.
Hydration and Water Consumption
Squirrels obtain the water necessary for digestion, temperature regulation, and metabolic function from both direct sources and the food they consume. They have a relatively low daily water requirement, with much of their hydration coming from metabolic water and the moisture content of their diet. Succulent plants, fruits, and fungi contribute significantly to their fluid intake.
When environmental conditions are dry or their diet consists mostly of hard nuts and seeds, they must seek external water sources. These include natural reservoirs like small puddles, streams, and dew that collects on leaves and grass. Urban squirrels frequently use man-made sources such as bird baths, pet water dishes, or condensation on outdoor equipment.
A healthy squirrel will generally exhibit a strong thirst drive, but in times of extreme heat or illness, dehydration can occur. Signs of severe dehydration include a lethargic appearance, sunken eyes, and dry or sticky gums. The small amount of water they require daily can increase dramatically in hot weather or for lactating females.
Unsafe and Toxic Foods
While squirrels are adaptable foragers, certain items are toxic or highly detrimental to their health, particularly those encountered in human environments. Chocolate and caffeinated products contain theobromine, a stimulant compound rodents cannot metabolize efficiently; even small amounts can cause seizures or cardiac issues. High-sodium foods like salted nuts, chips, and pretzels can quickly lead to severe dehydration and kidney stress.
Processed human foods, including bread, crackers, and sugary snacks, offer minimal nutritional value and can cause digestive blockages or nutritional deficiencies. A diet high in starches and simple sugars displaces the intake of nutrient-dense forage required for survival. Raw peanuts, which are legumes and not true nuts, may contain aflatoxin, a potentially toxic fungus that can cause liver damage.
Products meant for other species, such as commercial dog or cat food, are inappropriate due to their unbalanced nutrient profile. These items often contain improper ratios of calcium and phosphorus, which can lead to metabolic bone disease. Squirrels should avoid avocado pits and skins, which contain the toxin persin, as well as onions and garlic, which can damage red blood cells.