During the night, when there is enough moisture in the air to keep them from becoming desiccated, spadefoot toads come out of their burrows to hunt for food. The adult diet generally consists of invertebrates, including beetles, snails, spiders, and caterpillars. The diets of spadefoot tadpoles are much more remarkable. Most anuran larvae eat vegetative matter, but spadefoot larvae include some of the few species that eat aquatic insects and small crustaceans as well. They also eat plant material, filtering particles from the water column. Spadefoot tadpoles sometimes group together in huge schools, which may help stir up settled plant material from the bottom of the pond. Schooling also may help protect against predation by insect larvae. Because spadefoots breed in relatively shallow, temporary waters, they are under constant stress from drying waters, increasing temperatures, reduced food densities, and crowding. If the density of tadpoles reaches a certain point, some of the larvae of certain species eat their fellow tadpoles. The cannibal morphs develop larger heads, sharp beaks, strong jaw muscles, and shortened intestines. Research indicates that cannibalism is adaptive in these species, because it allows for increased caloric intake, which, in turn, accelerates the rate of growth of the tadpoles. This ensures that the larvae reach the necessary size to metamorphose before the pond dries. Research also indicates that the cannibals use chemical cues to recognize related tadpoles and avoid eating their close relatives.