Most species eat insects, spiders, worms, and slugs. However, some of the larger species are able to eat larger prey like mice, birds, and small reptiles. Their skin absorbs water so they don’t need to drink water. Frogs help keep a large part of the world’s insect population under control. Frogs vary widely in size and weight depending on species. For example, the West African goliath frog can grow to 15 inches and weigh as much as 7 pounds. Meanwhile, the Cuban tree frog grows to only half an inch and weighs approximately 2 ounces.