These are the spadefoot toads, amphibians, most occurring in and adapted to arid climates. But when it rains hard, they are out taking advantage in an orgy of chorusing, egg-laying, feeding, and rapid metamorphosis. In some areas, they may stay underground for several years encased in a hardened mucous to be dissolved by the next penetrating serious rains. One sequence of 3 pictures shows recently emerging spadefoot tadpole rapidly absorbing its tail into its body mass.
The sequence on Couch's Spadefoots shows tadpoles schooling and in feeding frenzy (within 7 days of egg laying), all designed to metamorphose before the pools dry up.