Among prolonged breeders

Like other amphibians, the life cycle of a frog normally starts in water with an egg that hatches into a limbless larva with gills, commonly known as a tadpole. After further growth, during which it develops limbs and lungs, the tadpole undergoes metamorphosis in which its appearance and internal organs are rearranged. After this it is able to leave the water as a miniature, air-breathing frog.

Reproduction

Two main types of reproduction occur in frogs, prolonged breeding and explosive breeding. In the former, adopted by the majority of species, adult frogs at certain times of year assemble at a pond, lake or stream to breed. Many frogs return to the bodies of water in which they developed as larvae. This often results in annual migrations involving thousands of individuals. In explosive breeders, mature adult frogs arrive at breeding sites in response to certain trigger factors such as rainfall occurring in an arid area. In these frogs, mating and spawning take place promptly and the speed of larval growth is rapid in order to make use of the ephemeral pools before they dry up.[103]

Among prolonged breeders, males usually arrive at the breeding site first and remain there for some time whereas females tend to arrive later and depart soon after they have spawned. This means that males outnumber females at the water's edge and defend territories from which they expel other males. They advertise their presence by calling, often alternating their croaks with neighbouring frogs. Larger, stronger males tend to have deeper calls and maintain higher quality territories. Females select their mates at least partly on the basis of the depth of their voice.[104] In some species there are satellite males who have no territory and do not call. They may intercept females that are approaching a calling male or take over a vacated territory. Calling is an energy-sapping activity. Sometimes the two roles are reversed and a calling male gives up its territory and becomes a satellite