Several common foods can sicken or kill grey squirrels, including some that people regularly leave out thinking they’re helpful. The most dangerous fall into a few categories: foods containing natural plant toxins, mold-contaminated nuts and grains, and everyday human foods that overwhelm a squirrel’s small body.
Raw Peanuts and Corn
Raw peanuts are one of the most widely offered squirrel foods, and one of the riskiest. The problem isn’t the peanut itself but aflatoxin, a potent mold toxin produced by fungi that colonize peanuts in storage. An estimated 80% of stored peanuts develop aflatoxin mold beneath the shell, and the dust from this mold coats the nut. When a squirrel shells and eats the peanut, it ingests the toxin along with it.
Aflatoxins are known carcinogens that accumulate in the body over time. In squirrels, chronic exposure leads to organ dysfunction, internal bleeding, and eventually a painful death. A squirrel eating a few contaminated peanuts won’t drop dead on the spot, which is part of what makes the risk so easy to miss. The damage builds quietly. Raw corn carries similar aflatoxin risks. If you want to offer peanuts, roasted and unsalted varieties are safer because the roasting process reduces (though doesn’t eliminate) mold contamination.
Beyond aflatoxin, peanuts create a second problem when fed in large quantities. They have a poor calcium-to-phosphorus ratio, and squirrels that eat too many of them can develop metabolic bone disease, a painful condition where bones weaken and fracture. More on that below.
Fruit Pits and Seeds
The pits of stone fruits like apricots, peaches, cherries, and plums contain amygdalin, a compound that releases cyanide when digested. A squirrel’s small body weight means it takes far less cyanide to reach a dangerous dose than it would for a human. Mild exposure causes breathing difficulty, weakness, and lightheadedness. Severe exposure leads to seizures, cardiovascular collapse, and death. Apple seeds contain the same compound in smaller concentrations.
Squirrels in the wild occasionally encounter these fruits but tend to eat the flesh and discard the pit. The danger increases when people leave out bowls of cut fruit with pits intact, or when squirrels raid compost bins full of stone fruit waste. If you’re putting out fruit for squirrels, remove all pits and large seeds first.
Avocado
Every part of an avocado plant, including the fruit’s skin and pit, contains persin, a toxin that varies in severity across species. Rodents are especially sensitive to it, according to the ASPCA. In affected animals, persin causes vomiting, diarrhea, and potentially more serious organ damage. The flesh of a ripe avocado contains lower concentrations than the skin or pit, but the safest approach is to keep avocados away from squirrels entirely.
Nightshade Plants
If you grow tomatoes, peppers, potatoes, or eggplant, squirrels may encounter solanine, a toxic compound found in nightshade family plants. The highest concentrations appear in unripe berries and green plant tissue, with ripe fruit containing the least. In large doses, solanine slows the heart, drops body temperature, and causes trembling, convulsions, and potentially death. Lab mice fed nightshade fruit of varying ripeness showed gastrointestinal problems and behavioral changes.
Green potatoes and potato sprouts are particularly concentrated sources. Ripe tomato flesh is relatively low in solanine, but the leaves and stems of tomato plants are not safe. If squirrels are raiding your garden, the green, unripe produce poses more risk than the ripe fruit.
Chocolate and Caffeine
Chocolate contains theobromine, a compound that small mammals metabolize very slowly. The darker the chocolate, the higher the theobromine content and the greater the danger. A squirrel weighs roughly 400 to 600 grams, so even a small amount of dark chocolate delivers a proportionally massive dose. Caffeine poses a parallel risk. Research on squirrel monkeys found that some primates have a dramatically longer caffeine half-life (11 hours versus 2 to 5 hours in other species), illustrating how caffeine clearance varies widely across animals. Grey squirrels, with their tiny body mass, are similarly vulnerable to caffeine’s effects on heart rate and the nervous system.
Salty and Processed Human Foods
Chips, crackers, salted nuts, bread, and other processed snacks are common offerings that cause real harm. A squirrel’s kidneys are not built to handle concentrated salt loads. Excess sodium pulls water from cells and can cause dehydration, neurological symptoms, and organ stress. Beyond salt, processed foods are nutritionally empty for squirrels and displace the natural foods they need. A squirrel that fills up on bread or chips isn’t eating the nuts, seeds, and vegetation that provide essential minerals.
Foods That Cause Metabolic Bone Disease
This is the slow-motion danger that doesn’t look like poisoning but can be just as deadly. Metabolic bone disease (MBD) develops when a squirrel’s diet contains too much phosphorus relative to calcium. The ideal ratio is about 2 parts calcium to 1 part phosphorus. When the ratio drops below 1:1, the squirrel’s body starts pulling calcium from its bones to maintain blood calcium levels, and the skeleton gradually weakens.
Peanuts, sunflower seeds, and corn are all high in phosphorus and low in calcium. Fed as occasional treats, they’re fine. Fed as the main diet, they’re a recipe for MBD. Squirrels with this condition develop tremors, difficulty climbing, rubbery or deformed limbs, and eventually fractures from normal activity. Adequate vitamin D3 is also essential because it helps the body absorb calcium. Squirrels that spend time in sunlight generally produce enough on their own, but captive or heavily urban squirrels that rely on handouts may not.
If you regularly feed squirrels, balancing the calcium-to-phosphorus ratio matters more than any single food choice. Offering calcium-rich foods like broccoli, kale, almonds, or commercially available wildlife blocks alongside seeds and nuts helps prevent the slow mineral depletion that leads to MBD.
Signs a Squirrel Has Eaten Something Toxic
Squirrels that have ingested a toxin typically show a combination of lethargy, loss of coordination, and visible distress. Depending on the substance, you might notice labored breathing, trembling, an inability to climb or balance, or the squirrel sitting hunched and unresponsive. Gastrointestinal toxins often produce vomiting or diarrhea. Neurological poisons lead to confusion, circling, or seizures. A squirrel with MBD may drag its hind legs or have visibly swollen joints.
If you find a squirrel displaying these symptoms, contact a local wildlife rehabilitator rather than attempting treatment yourself. Many toxin exposures are survivable with professional care, especially if caught early.