Squirrels are far more than just the acorn-obsessed acrobats of the animal kingdom. While the image of a bushy-tailed rodent clutching a nut is iconic, their actual diet is complex, opportunistic, and surprisingly varied. These animals are classified as omnivores, meaning they consume a strategic mix of plant matter and animal protein to survive the changing seasons. Understanding what squirrels eat requires a look beyond the bird feeder and into the intricate seasonal cycles of the forests and suburban landscapes they call home.

The Foundation: Nuts, Seeds, and Hard Mast

For most tree squirrels, such as the Eastern Gray Squirrel or the Fox Squirrel, the primary source of nutrition comes from "hard mast." This term refers to the hard-shelled seeds of woody shrubs and trees. These high-fat, high-energy foods are the backbone of a squirrel's survival, especially as they prepare for the lean winter months.

Acorns: The Golden Standard

Acorns from oak trees are perhaps the most critical food source. However, squirrels are selective about which acorns they consume immediately and which they bury. Oak trees are generally divided into two groups: white oaks and red oaks. White oak acorns tend to sprout quickly after falling, which uses up their stored energy. Consequently, squirrels often eat these immediately. Red oak acorns contain higher levels of tannins—bitter chemicals that act as a preservative—and don't sprout until spring. Squirrels recognize this and are more likely to cache red oak acorns for winter consumption.

Walnuts and Hickory Nuts

Walnuts and hickory nuts offer a significantly higher fat content than acorns. The thick, rugged shells of these nuts require the squirrel's specialized incisors to work through. A squirrel’s teeth never stop growing, and gnawing on these hard shells helps keep their teeth at a manageable length. When you see a squirrel seemingly "struggling" with a large walnut, it is actually engaging in a vital biological maintenance task while securing a calorie-dense meal.

Pine Seeds and Cones

Red squirrels, often found in coniferous forests, rely heavily on pine seeds. They often harvest green pine cones before they open, stripping the scales away to reach the seeds inside. These squirrels are known for creating "middens"—large piles of discarded cone scales that can accumulate over generations, marking a highly defended food territory.

The Omnivorous Side: Insects and Animal Protein

A common misconception is that squirrels are strict vegetarians. In reality, when high-energy plant foods are scarce or when a squirrel needs a boost of protein (such as during the breeding season), they turn to animal sources. This behavior is more frequent than casual observers might realize.

Insects and Larvae

Squirrels frequently consume caterpillars, beetles, grasshoppers, and various larvae. These provide essential amino acids that are difficult to find in a nut-heavy diet. Ground squirrels, in particular, spend a significant amount of time foraging in the soil for grubs and beetles.

Bird Eggs and Nestlings

While it may be distressing to bird watchers, squirrels are known nest predators. They may raid the nests of songbirds to consume eggs or even young nestlings. This typically happens in late spring and early summer when the squirrels' nutritional demands are high due to rearing their own young. The calcium found in eggshells is also a valuable mineral for lactating female squirrels.

Carrion and Small Vertebrates

In extreme circumstances or when the opportunity arises, some squirrels have been observed eating carrion (decomposing animal meat). There are even documented cases of larger squirrel species, like the Fox Squirrel, hunting small vertebrates such as frogs, toads, or even other smaller rodents. While not a primary food source, this flexibility ensures survival during periods of environmental stress.

Seasonal Delicacies: From Spring Buds to Autumn Berries

The diet of a squirrel is dictated by the calendar. They are masters of eating what is "in season," shifting their focus as different plants reach various stages of growth.

Early Spring: The Hunger Gap

Early spring is often the most difficult time for squirrels. The nuts they buried in the autumn have either sprouted (making them less nutritious) or have been stolen by other animals. During this "hunger gap," squirrels rely heavily on tree buds and flowers. Maple, oak, and elm buds provide a vital source of moisture and high-energy sugars. You may notice squirrels hanging precariously from the ends of thin branches in April; they are likely reaching for the tender new growth of red or sugar maples.

Summer: Fruits and Berries

As the weather warms, squirrels diversify into "soft mast." This includes a wide variety of wild fruits and berries. They are particularly fond of:

  • Wild Cherries and Mulberries: These provide quick bursts of energy through natural sugars.
  • Dogwood and Black Gum Fruits: These are often high in fats, helping the squirrel maintain its condition through the summer heat.
  • Apples and Pears: In suburban environments, backyard fruit trees are a prime target. Squirrels often take a few bites of a ripening fruit before discarding it, a habit that can be frustrating for gardeners.

Late Summer: Corn and Cultivated Grains

In rural areas, squirrels are known to visit cornfields. Interestingly, they often don't eat the entire kernel of corn. Instead, they use their precise teeth to remove the "germ" at the base of the kernel—the part richest in protein and fats—and discard the starchy remainder.

The Role of Fungi and Mushrooms

Squirrels are among the few mammals that can safely consume a variety of fungi, including some that are toxic to humans. They are often seen carrying large mushrooms up into trees, where they wedge them into the crooks of branches to dry. Drying the mushrooms prevents them from rotting and may also neutralize certain toxins.

Truffles and Underground Fungi

Flying squirrels have a particularly unique relationship with fungi. They often forage on the ground at night for truffles and other underground fungal bodies. By eating these fungi and then traveling through the canopy, flying squirrels play a crucial role in dispersing fungal spores across the forest floor, which in turn helps trees absorb nutrients more effectively. This symbiotic relationship is a cornerstone of forest health.

Species-Specific Dietary Habits

While there is much overlap, different squirrel species have evolved to exploit specific niches in their environments.

Eastern Gray Squirrel

As the most common species in North America, the Gray Squirrel is a generalist. It is a "scatter hoarder," meaning it buries thousands of individual nuts across a wide area. Because they fail to recover many of these nuts, Gray Squirrels are one of nature's most effective reforestation agents.

Red Squirrel

Red squirrels are more specialized towards coniferous forests. They are "larder hoarders," preferring to store a massive cache of food in a single location, such as a hollow log or a specific hole in the ground. They are also much more territorial and will vocally defend their food stores against larger squirrels.

Southern Flying Squirrel

Being nocturnal, the Flying Squirrel has a diet that includes more night-active insects and a higher proportion of fungi. They also have a notable fondness for tree sap. In the early spring, they may lick the sap that flows from wounds in maple trees, providing them with a much-needed mineral and sugar boost.

Squirrels in the Human Landscape

In urban and suburban settings, squirrels have adapted their diets to include human-provided resources. This brings both benefits and risks to the animals.

The Bird Feeder Conflict

Squirrels are notorious for raiding bird feeders. Sunflower seeds, peanuts, and suet are extremely high in calories, making them an irresistible target. While these foods are not inherently "bad" for squirrels, a diet consisting purely of birdseed can lead to nutritional imbalances, specifically a lack of calcium.

Garden Raids and Bulbs

If you find your spring tulips disappearing, squirrels might be the culprit. They are known to dig up and eat flower bulbs, which provide a starch-rich food source in the late winter and early spring. They may also target vegetable gardens, eating everything from tomatoes to squash, often just as the produce is reaching peak ripeness.

What You Should Not Feed Squirrels

If you enjoy feeding squirrels in your backyard, it is important to avoid certain items that can be harmful to their health:

  • Salted Nuts: High sodium intake is dangerous for small rodents.
  • Dairy Products: Squirrels are largely lactose intolerant.
  • Junk Food: Crackers, bread, and sugary cereals provide "empty calories" that can lead to obesity and poor bone health.
  • Raw Peanuts: Some raw peanuts can harbor Aspergillus flavus, a fungus that produces aflatoxin, which is toxic to squirrels. Roasted, unsalted peanuts are a safer alternative if fed in moderation.

Hydration: How Squirrels Drink

Squirrels require a consistent source of water, but they don't always need to visit a pond or stream. Much of their hydration comes from their food. Fungi, succulent buds, and fruits have high moisture content. In the winter, squirrels will eat snow to stay hydrated. However, during heatwaves or droughts, they will actively seek out standing water, including birdbaths, pet water bowls, and even dripping outdoor faucets.

The Survival Strategy of Food Storage

The way a squirrel handles its food is just as important as what it eats. The act of "caching" is a sophisticated survival mechanism. Squirrels use their keen sense of smell to relocate buried nuts, even under a foot of snow. Interestingly, research suggests they don't just rely on smell; they also use a form of spatial memory to remember the general areas where they have hidden their treasures.

By scatter-hoarding, Gray Squirrels reduce the risk of losing their entire winter supply to a single thief. Conversely, the Red Squirrel’s larder-hoarding strategy is high-risk but high-reward, allowing them to guard a concentrated wealth of resources in the dense cover of pine forests.

Conclusion: A Balanced Ecosystem Role

Everything a squirrel eats has an impact on the environment. By consuming seeds and burying them, they plant the forests of the future. By eating insects, they help control pest populations. Even their habit of raiding bird nests, while difficult to watch, is a natural part of the checks and balances within an ecosystem.

Whether they are nibbling on a maple bud in the spring or meticulously deconstructing a hickory nut in the fall, squirrels are highly efficient foragers. Their ability to adapt to diverse environments—from deep wilderness to city parks—is a testament to their flexible and opportunistic diet. Next time you see a squirrel in your yard, take a closer look at what it’s carrying; you might be surprised to see that it’s not just an acorn, but a complex piece of a much larger ecological puzzle.