A few of the larger ones may eat other frogs

At the end of the tadpole stage, a frog undergoes metamorphosis in which its body makes a sudden transition into the adult form. This metamorphosis typically lasts only 24 hours, and is initiated by production of the hormone thyroxine. This causes different tissues to develop in different ways. The principal changes that take place include the development of the lungs and the disappearance of the gills and gill pouch, making the front legs visible. The lower jaw transforms into the big mandible of the carnivorous adult, and the long, spiral gut of the herbivorous tadpole is replaced by the typical short gut of a predator.[114] The nervous system becomes adapted for hearing and stereoscopic vision, and for new methods of locomotion and feeding.[114] The eyes are repositioned higher up on the head and the eyelids and associated glands are formed. The eardrum, middle ear, and inner ear are developed. The skin becomes thicker and tougher, the lateral line system is lost, and skin glands are developed.[114] The final stage is the disappearance of the tail, but this takes place rather later, the tissue being used to produce a spurt of growth in the limbs.[120] Frogs are at their most vulnerable to predators when they are undergoing metamorphosis. At this time, the tail is being lost and locomotion by means of limbs is only just becoming established
After metamorphosis, young adults may disperse into terrestrial habitats or continue to live in water. Almost all species of frogs are carnivorous as adults, preying on invertebrates, including arthropods, worms, snails, and slugs. A few of the larger ones may eat other frogs, small mammals, and fish. Some frogs use their sticky tongues to catch fast-moving prey, while others push food into their mouths with their hands. The tree frog Xenohyla truncata is a partly herbivorous exception, its diet including a large proportion of fruit.[121] Adult frogs are themselves attacked by many predators. The northern leopard frog (Rana pipiens) is eaten by herons, hawks, fish, large salamanders, snakes, raccoons, skunks, mink, bullfrogs, and other animals