What Do Squirrels Eat? Foods to Offer and Avoid

Squirrels are opportunistic omnivores whose diet spans nuts, seeds, fruit, fungi, plant buds, insects, and occasionally eggs or small vertebrates. If you’re thinking about putting food out for them, the best options mirror what they forage naturally: hard-shelled nuts, certain seeds, and vegetables, while processed human foods, salted snacks, and a few specific raw items can cause real harm. The details matter more than you might expect, because squirrels have specific nutritional needs that even well-intentioned feeding can miss.

What Wild Squirrels Actually Eat

The common backyard squirrel in North America is usually an eastern gray squirrel, but the broad dietary pattern holds across most tree squirrel species. Their staple foods are tree nuts and seeds: acorns, walnuts, hickory nuts, hazelnuts, pine seeds, and whatever mast (the collective term for tree-produced nuts and seeds) is available in their habitat. Beyond that, they eat fruit, flower buds, bark, mushrooms, and insects. They are not strict herbivores. Gray squirrels regularly eat insect larvae found inside acorns, and in one study, squirrels consumed weevil larvae from infested acorns in more than 76% of feeding trials.¹ Those larvae are a meaningful protein and fat supplement, not just an accidental snack.

Different squirrel species carve out slightly different dietary niches even when they share the same forest. Research comparing eastern gray squirrels, red squirrels, and flying squirrels using isotopic analysis found that gray and red squirrels had comparably broad diets, while flying squirrels had a much narrower dietary range.² Flying squirrels lean heavily on fungi, while gray and red squirrels are more generalist. If you’re feeding squirrels in your yard, you’re almost certainly dealing with gray squirrels or fox squirrels, both of which eat a wide range of foods.

How Their Diet Shifts With the Seasons

Squirrels do not eat the same things year-round. In autumn, when trees produce their mast crop, nuts and seeds dominate the diet. Squirrels cache thousands of acorns and nuts during this period, burying them individually across a wide area for retrieval over winter and into spring. By late winter and early spring, cached nuts start running out and fresh mast hasn’t been produced yet. During this lean period, squirrels shift to whatever is available: tree buds, bark, early flowers, and fungi.

A study of Eurasian red squirrels found that rural squirrels compensated for spring seed scarcity by eating more plant material, while urban squirrels continued eating seeds through the spring, likely because of supplemental food from bird feeders and people.³ This matters if you feed squirrels: you are effectively flattening out their seasonal diet, which can be helpful during genuine scarcity but may also reduce their motivation to forage naturally.

This seasonal cycle also explains some behaviors that puzzle people. Squirrels stripping bark from trees in spring isn’t random vandalism. The bark of certain species, particularly oak and beech, contains far more calcium relative to phosphorus than the nuts and seeds squirrels eat the rest of the year.⁴ Bark stripping may be a way to correct a mineral imbalance, particularly for younger, growing squirrels that need calcium for bone development.

The Calcium-to-Phosphorus Problem

This is one of the least appreciated aspects of squirrel nutrition, and it directly affects what you should offer. Nuts and seeds, the foods most people associate with squirrels, are generally low in calcium relative to phosphorus. Acorns, hazelnuts, and most other tree seeds have a calcium-to-phosphorus ratio that is inverted compared to what growing mammals need. Fungi and insects are similarly imbalanced, with one notable exception: woodlice (pill bugs) are unusually high in calcium.⁴

Wild squirrels compensate by eating bone fragments, antler sheds, bark, and soil. In captivity or heavy supplemental feeding situations, squirrels that only get nuts and seeds can develop metabolic bone disease, a painful condition where bones soften and fracture. If you regularly feed squirrels, including a calcium source helps. Cuttlebone (the same thing sold for pet birds), pieces of deer antler, or calcium-rich vegetables like broccoli and kale can fill the gap. Simply dumping out peanuts every day, as popular as that is, does not give squirrels a balanced diet.

Safe Foods to Offer

The best foods for squirrels are the ones closest to their natural diet. Here’s what works well:

Hard-shelled nuts: Walnuts, pecans, hickory nuts, and hazelnuts in the shell are ideal. The shell provides gnawing exercise that keeps their continuously growing incisors worn down, and the nut inside is calorie-dense and nutrient-appropriate.
Acorns: White oak acorns are preferred. Red oak acorns are higher in tannins, which reduce protein digestibility and can suppress food intake if eaten in large quantities.⁵ Squirrels in the wild handle this by eating a mix and caching red oak acorns for later rather than eating them immediately, but if you’re collecting acorns to offer, white oak is the better choice.
Vegetables: Broccoli, kale, squash, sweet potato, and zucchini. These offer vitamins and minerals that nuts alone don’t provide, and leafy greens contribute calcium.
Fruit in moderation: Apple slices, berries, grapes, and banana pieces. Fruit is high in sugar, so it works better as an occasional treat than a staple.
Mushrooms: Fresh button mushrooms, shiitake, and similar common edible fungi are safe and reflect what squirrels eat naturally.
Sunflower seeds and pumpkin seeds: Fine in moderation, though both are high in fat and low in calcium, so they shouldn’t be the only offering.

Peanuts deserve a separate mention because they’re what most people offer first. Peanuts are not actually tree nuts; they’re legumes, and they aren’t part of a squirrel’s natural diet. They’re not toxic, but they’re nutritionally inferior to tree nuts for squirrels. Raw peanuts can harbor a mold that produces aflatoxin, which is harmful. If you do offer peanuts, roasted and unsalted is the safer option, and they should be part of a broader mix rather than the sole food.

Foods to Avoid

Some foods that seem harmless can cause genuine problems:

Salted or flavored nuts: Squirrels can’t process large amounts of sodium. Salted peanuts, cashews, or other seasoned snacks can damage their kidneys over time.
Corn: Dried corn is extremely low in nutritional value for squirrels and fills them up without providing the protein and fat they need. It’s also prone to aflatoxin contamination. Fresh corn on the cob in small amounts is less problematic, but it shouldn’t be a regular offering.
Bread, crackers, and cereal: These processed carbohydrates offer almost nothing nutritionally. Squirrels will eat them readily, which is part of the problem: they fill up on empty calories and forage less for nutritious food.
Chocolate and candy: Theobromine in chocolate is toxic to squirrels, as it is to most small mammals. Sugary foods in general promote dental problems and obesity.
Raw red kidney beans: These contain phytohemagglutinin, a lectin that is toxic when uncooked. Other raw dried beans can cause similar issues.
Fruit pits and seeds: Apple seeds, cherry pits, peach pits, and similar stone fruit seeds contain amygdalin, which converts to cyanide during digestion. The flesh of these fruits is fine; the pits are not.

A general rule: if it’s processed, seasoned, or designed for human snacking, keep it away from squirrels. Their digestive systems evolved to handle raw, whole plant foods and animal protein, not refined starches and sodium.

How Squirrels Decide What to Eat and What to Bury

One of the more fascinating aspects of squirrel behavior is how carefully they evaluate food before deciding whether to eat it now or store it. Gray squirrels can distinguish between sound acorns and those infested with weevil larvae, and they handle each differently. In studies, squirrels cached 20 to 35% more intact red oak acorns than infested ones, and they carried those intact acorns significantly farther from the source tree before burying them.¹ Infested acorns, by contrast, were typically eaten on the spot, larvae and all.

This selectivity extends to the quality and species of acorn. Fox squirrels have been shown to preferentially disperse heavier, non-infested acorns over longer distances, while consuming lower-quality acorns close to the parent tree. Nutritionally richer acorn species were also carried farther and cached more carefully.⁶ The squirrel is essentially investing more effort in storing the food that’s worth retrieving later.

White oak acorns present an interesting wrinkle. They germinate soon after falling, which means storing them for months is pointless because the nut’s energy will have already gone into a sprouting root. Squirrels seem to know this, and research shows they eat significantly more white oak acorns immediately rather than caching them.¹ Red oak acorns, which lie dormant through winter and germinate in spring, are the ones squirrels invest in burying. Some squirrels even bite out the embryo of cached acorns to prevent germination while preserving the rest of the nut’s nutrients.

The practical takeaway: if you put out food for squirrels, they won’t just eat everything immediately. They’ll assess quality, eat some, and carry the rest away for caching. Offering nuts in the shell lets them exercise this natural behavior rather than simply consuming everything at the feeder.

The Tannin Trade-Off in Acorns

If you’re in an area with oak trees and thinking about gathering acorns to put out, the difference between red oak and white oak acorns is worth understanding. Red oak acorns contain substantially higher levels of phenols and tannins than white oak acorns. When gray squirrels were fed a diet of 100% red oak acorns in experimental conditions, they showed reduced protein digestibility and lower food intake, and their livers ramped up detoxification activity to handle the tannin load.⁵ White oak acorn diets caused some reduction in protein digestibility compared to a tannin-free reference diet, but didn’t suppress appetite or trigger the same detoxification response.

In the wild, squirrels manage tannin exposure by mixing their diet. They don’t eat only red oak acorns for days on end. But if you’re supplementing their diet with gathered acorns, offering predominantly white oak acorns and mixing in other foods is the more nutritionally sound approach. You can tell them apart visually: white oak acorns have rounded, bumpy caps and tend to be less pointed, while red oak acorns have flatter, tighter caps and a more elongated shape.

Feeding Squirrels and What It Means for Local Birds

Many people who feed squirrels do so through bird feeders, either intentionally or because the squirrels help themselves. This raises a real ecological question. A UK study found that gray squirrels were frequent visitors to filled bird feeders and that nest predation by squirrels, magpies, and jays was significantly higher near filled feeders compared to empty or absent ones.⁷ Concentrating food attracts predators, and squirrels will opportunistically raid bird nests for eggs and nestlings when they’re already in the area.

That said, the relationship between feeders and squirrel populations is more complicated than “feeders attract squirrels.” A study of urban American robins and northern cardinals found that the number of bird feeders in an area was not significantly related to the relative abundance of squirrels.⁸ Squirrel populations are driven more by habitat, den availability, and natural mast production than by the presence of feeders. But feeders do change where squirrels concentrate their activity, and that localized concentration near nesting birds is where the problem arises.

If you want to feed squirrels without increasing pressure on nesting birds, placing a dedicated squirrel feeder away from areas where birds nest is a reasonable compromise. Squirrel-specific feeders stocked with nuts and corn (as a lure, not a nutritional staple) can draw them to a particular spot. Timing matters too: during spring nesting season, keeping feeders farther from hedges and shrubs where birds nest reduces the overlap.

Fungi, Truffles, and the Forest Connection

One of the more surprising items on the squirrel menu is underground fungi. Red squirrels and eastern chipmunks eat truffles and other below-ground fruiting fungi regularly. A dietary survey in northwestern Ontario found remains from at least five genera of truffle fungi in squirrel scat, along with spores from above-ground mushrooms including boletes and other forest-floor species.⁹

This isn’t just a quirky food preference. Those underground fungi form symbiotic relationships with tree roots, helping trees absorb water and nutrients from the soil. When squirrels eat truffles and then defecate elsewhere in the forest, they spread fungal spores to new locations. In ecosystems where wind can’t disperse these spores (because the fungi fruit underground), animals like squirrels are the primary dispersal mechanism. Northern flying squirrels are especially dependent on this food source. Research in the Rocky Mountains found that flying squirrels preferred underground fungi over arboreal lichens in feeding trials, and they maintained a positive nitrogen balance on fungal diets but could not do so on lichen alone.¹⁰

You won’t be putting truffles out on your back porch, but this relationship illustrates something useful about squirrel nutrition more broadly. They evolved eating a wide variety of foods that fulfill different nutritional roles. Fungi provide bulk and some minerals. Nuts and seeds provide fat and energy. Insects provide protein. Bark and leafy material provide calcium and fiber. Any feeding strategy that narrows this down to a single food type, no matter how calorie-dense, is doing the squirrel a disservice. The most helpful approach is variety: rotate what you offer, include both high-fat and high-calcium foods, keep things raw and unseasoned, and let the squirrels sort out the rest. They’ve been making smart food decisions for millions of years.

1
Journal of Mammalogy. Caching and Feeding Decisions by Sciurus carolinensis: Responses to Weevil-Infested Acorns
2
Food Webs. Quantifying niche partitioning and multichannel feeding among tree squirrels
3
Journal of Mammalogy. Supplemental feedings affect diet seasonality and niche width in urban Eurasian red squirrels
4
Forest Ecology and Management. A novel causal mechanism for grey squirrel bark stripping: The Calcium Hypothesis
5
PubMed. Effects of tannins on digestion and detoxification activity in gray squirrels (Sciurus carolinensis)
6
PubMed. Tree Squirrels Selectively Disperse High-Quality Acorns Away From Tree Trunks
7
Ibis. Provision of supplementary food for wild birds may increase the risk of local nest predation
8
Ornithological Applications. Species-dependent effects of bird feeders on nest predators and nest survival of urban American Robins and Northern Cardinals
9
The Canadian Field-Naturalist. Consumption of Truffles and other Fungi by the American Red Squirrel (Tamiasciurus hudsonicus) and the Eastern Chipmunk (Tamias striatus) (Sciuridae) in Northwestern Ontario
10
Canadian Journal of Zoology. Nutritional value and diet preference of arboreal lichens and hypogeous fungi for small mammals in the Rocky Mountains