Frogs are predators. A handful of species have been recorded eating plant material, including small fruits, but these are very much the exception. Ninety nine percent of adult frogs eat other animals. To be prey for a frog, the animal must be of a size that can be overpowered by the frog’s mouth alone. The front legs of the frog are not powerful and do not have claws. Their feet are of no use in capturing prey or in tearing it into bite size pieces. The absence of these supporting weapons thus places a lot of responsibility of the frog mouth. A frog must capture prey using only its mouth; the whole prey must fit inside of its mouth, and the frog must be able to swallow the sometimes large and actively struggling animal with its mouth alone. And what a mouth it is.

The great gape of most frog mouths enables them to take on surprisingly large prey and provides a base for their specialized long range weapon, the tongue. “Long-Range”, of course, is a relative term, and no frog’s tongue is comparable in length to a chameleon’s for example. The frogs tongue at rest folds on the floor of the mouth. It is normally attached to the front of the lower jaw rather than at the back, as in people and many other animals. This attachment gives the frog maximum range for launching the tongue to catch insects. As the tongue lies folded in the mouth, the sticky portion at the tip of the tongue faces up. When its prey is within range, the frog opens its mouth and flips its tongue at the target. The prey is stuck to the tongue, which is quickly flipped back into the mouth. The action is very fast, sometimes a matter of milliseconds, and a human observer might not even realize that the tongue was involved. Once inside the jaws, the prey is swallowed as quickly as possible, sometimes aided by contractions of the eye muscles, which help push the prey down the throat.

Most frogs employ one of two basic hunting strategies. The most common strategy is the sit and wait technique. This technique is straightforward; choose a site frequented by prey species, count on your coloration and immobility for camouflage, and ambush anything that passes close enough. If the prey is near but not close enough, the frog may slowly lean forward or take a cautious step or two close to the range.

Some frogs have appended refinements on to the sit and wait method. The horned frogs of the New World tropics use their toes as lures to draw prey close to their camouflaged mouths. Ornate horned frogs have bright yellow toes on their hind feet, which they lift above their hindquarters. From frog eye level and in front, the yellow toes may be mistaken for a small flower, fruit, or insect resting above a nondescript piece of the rainforest floor.

Frogs eat almost anything that fits into their mouth. For most frogs “anything” means insects and other invertebrates. Frogs generally locate their prey by sight, but some species clearly posses a sense of smell. There is also a species of frog that does not even posses a tongue, as weird as that is, the aquatic pipids have no tongues and basically suck in food. As a final footnote to the unique aspect of hunting, I must mention the story of fang. Fang was a gray tree frog, and was a pet of mine. When I would arrive with a container of moths, Fang would immediately become agitated and start scrambling along the branches in his terrarium. I would normally, remove the lid deposit the moths, and let the games begin. Fang would stalk the moths. I realized that he felt the same way about moths that I felt about pizza. He could simply not stop eating them no matter how his stomach was distended and sagging from the presence of three or four large moths. It was pathetic yet amusing to watch him try and haul himself within range of yet another moth, sometimes with a moth wing still protruding from his mouth. I was greatly impressed by his commitment.