Acoustic communication and reproductive behaviour in the aquatic frog Xenopus laevis (Pipidae), a field study

We studied the acoustic and reproductive behaviour of the clawed frog, Xenopus laevis, in a pond with clear water in South Africa over a period of two months. It contained 21 adult males and females. Each was marked with a transponder so that the behaviour of individuals could be tracked. The animals inhabited the bottom of the pond. They were active from dusk to midnight. Series of nights in which several males called alternated with series without calling. Simultaneous calls were not synchronised. On nights when males called, several of them established territories on the bottom of the pond that they defended against other males. They delineated the territory by calling along its borders. When meeting a male intruder they emitted an encounter call, followed by a fighting call if they fought. At the end of a fight the loser emitted a release call. Territories could remain constant over several weeks. They were abandoned on nights without calling, but re-established by the same individuals at the same locations on nights with calling. When a female entered a territory, the male approached, started the courtship call and attempted amplexus. The female usually rejected the male while emitting a release call. Females spawned synchronously on one or two nights, with weeks without oviposition in-between. Eggs were laid individually or in small groups on hard structures all over the pond. The adults preyed upon the tadpoles and only a few single tadpoles remained after two weeks. Raising the water level stimulated calling activity.