Garter snakes are carnivorous and prey upon insects, slugs, worms, lizards, amphibians, rodents and sometimes fish. Certain species of garter snake, such as the ribbon snake, are particularly fond of frogs. Common garter snakes eat many different kinds of small animals, including other snakes.
Garter snakes mostly eat live prey but sometimes eat eggs as well. They appear to be immune to the toxic secretions that protect frogs and toads from other predators and can consume those amphibians without harm. In fact, a large part of their diet in the wild is often made up of frogs and toads. In addition, the snake's saliva may be toxic to some of its prey, easing the snake's ability to swallow. Garter snakes are incapable of chewing or tearing their prey, so it is always swallowed whole.