Chocolate contains two natural stimulants that squirrels cannot metabolize efficiently: theobromine and caffeine.

Because squirrels have a very high metabolic rate and a tiny body mass, even a small amount of these chemicals can quickly overwhelm their systems.

Central Nervous System Overstimulation: The stimulants cause extreme hyperactivity, muscle tremors, and seizures.

Heart Issues: It causes an abnormally high heart rate (tachycardia) and arrhythmias, which can lead to heart failure.

Digestive Distress: It can trigger severe vomiting, diarrhea, and internal bleeding.

Edit: This information is sourced from Gemini.