Capsaicin in cayenne pepper acts as a deterrent for most mammals

Cayenne pepper serves as a natural deterrent for many animals due to the presence of capsaicin, a chemical compound that triggers heat-sensing pain receptors. Most mammals, including rodents, deer, squirrels, dogs, and cats, find the spice unpleasant because capsaicin binds to the TRPV1 receptor, creating a perceived burning sensation.

However, birds possess a unique genetic advantage. They have a modified TRPV1 receptor that is significantly less sensitive to capsaicin, making them largely unaffected by the heat. This biological difference allows cayenne pepper to be used effectively in pest control, such as protecting bird feeders from squirrels without deterring the birds themselves.