Science Lesson Time: Caffeine is a type of organic chemical called an alkaloid. Plants make these chemicals to try and deter insects and small animals from feeding on them. In other words, alkaloids are some of nature's poisons. They are often particularly potent against small animals (because they can't take as much of a dose) and herbivores, because the evolutionary arms race is a son of a bitch. This is why the advice for giving pets caffeine is always going to be DON'T.