The diet of frogs varies depending on the species; most consume insects, snails, spiders and worms, while the larger varieties consume small fish, moles, mice, and even other frogs. Frogs consume primarily organisms that are smaller and lower on the food chain: flies, worms, centipedes and other crawling insects are among their favorites.
Frogs of all sizes consume primarily meat, and will only eat food that they catch alive. Unlike most small organisms, frogs do not eat plants and vegetation. The smallest species of frogs feast on worms, larvae, mosquitoes and flies while larger varieties, such as bullfrogs, may eat mice, rats, moles and even small fish. Frogs, like snakes and some reptiles, lack teeth to chew their food. They rely on their strong tongues to pull food into their mouths; frogs' tongues extend and snatch victims within seconds, before retracting back into their cavities, food and all, to trigger the next phase of digestion. After retrieving food, frogs rely on their strong and highly elastic throat muscles to stretch wide enough to accommodate the passage of whole food items. Depending on the size of food item consumed, frogs may go for long periods of time between meals, or might graze throughout the day to keep their energy levels high.