While squirrels consume nuts, their natural diet is varied, and over-reliance on human-provided nuts can be harmful. The dangers fall into two categories: acute toxicity from specific compounds, and chronic health decline caused by long-term nutritional imbalance. Understanding this distinction is key to promoting a healthy environment for wild and captive squirrels.
Nuts That Pose Specific Health Risks
Certain nuts and their storage methods can introduce biological toxins that cause immediate, acute harm. The most significant concern is aflatoxins, highly toxic compounds produced by fungi that thrive in warm, humid conditions, often contaminating poorly stored peanuts and corn. Aflatoxin ingestion leads to severe liver damage and is considered carcinogenic. Roasting the nuts can significantly reduce the risk of aflatoxin contamination, but the safest practice is ensuring all stored food is fresh and free of mold or discoloration.
Chemical Hazards
Beyond mold, raw bitter almonds introduce chemical hazards. These almonds contain amygdalin, which the body metabolizes into hydrogen cyanide. While commercial sweet almonds are safe, raw bitter almonds must be strictly avoided. Furthermore, nuts prepared for human consumption (salted, candied, or seasoned) should not be offered, as the additives introduce excessive sodium and refined sugars that squirrels tolerate poorly.
Nutritional Imbalance from Nut-Heavy Diets
The greatest long-term danger of a nut-heavy diet is a systemic nutritional deficiency. Most nuts, especially peanuts and sunflower seeds, are high in phosphorus and low in calcium. This imbalance is measured by the calcium-to-phosphorus (Ca:P) ratio, which ideally should be around 2:1 (twice as much calcium as phosphorus) to ensure healthy bone structure. When a squirrel consumes low-calcium, high-phosphorus foods, the excess phosphorus actively blocks the absorption of the limited calcium available.
Metabolic Bone Disease (MBD)
To maintain calcium levels necessary for nerve and muscle function, the squirrel’s body leaches calcium directly from its bones and teeth. This systemic depletion results in Metabolic Bone Disease (MBD), a painful condition where the skeletal structure weakens and becomes brittle. Early symptoms include lethargy, reluctance to climb, and unusual aggression. As the disease advances, it can lead to spontaneous bone fractures, neurological symptoms, and hind-limb paralysis. MBD is a severe and often fatal outcome.
Foods Beyond Nuts That Are Dangerous or Toxic
Many common household foods pose immediate toxic threats to squirrels. Chocolate is highly dangerous because it contains the methylxanthine compounds theobromine and caffeine. Squirrels lack the necessary enzymes to metabolize theobromine quickly, allowing it to build up to toxic levels. The resulting poisoning can cause hyperactivity, tremors, increased heart rate, and ultimately seizures or cardiac failure.
Processed Foods and Other Toxins
Another item to avoid is the avocado, particularly its skin and pit, which contain the fungicidal toxin persin. Persin is toxic to many small mammals, potentially causing respiratory distress and myocardial damage. Highly processed human foods also present a hazard due to their extreme nutritional profiles. Foods high in sodium, such as chips, can quickly lead to electrolyte imbalances. Candy and baked goods containing processed sugars and artificial sweeteners offer no beneficial nutrients and contribute to poor health.
Promoting a Safe and Balanced Diet
The safest diet for wild squirrels is the one they forage for naturally, including acorns, seeds, bark, fungi, and insects. When providing supplemental food, the goal is to correct the nutritional imbalances found in commercial nuts and seeds. High-quality, nutritionally balanced rodent blocks should form the foundation of any supplementary feeding program for squirrels under human care.
Safe Supplemental Options
For wild squirrels, offering alternatives rich in calcium and low in phosphorus helps counter the effects of poor foraging choices. Safe options include dark leafy greens like kale, collards, and dandelion greens, along with vegetables such as broccoli and squash. Small pieces of calcium-rich fruits, such as apples, can also be offered as a treat, though sugar content should be monitored. It is helpful to provide these calcium-rich foods alongside a consistent source of fresh, clean water. Limiting the total amount of supplemental food encourages the squirrel to continue foraging for its natural, varied diet.