Phonotaxis and chorus organization in African frogs

Abstract

Detailed studies of the phonotactic behavior and chorus organization of several species of African amphibians were conducted from 1982–1992. A range of phonotactic experiments conducted in two- and three-dimensional arenas, using between one and four loudspeakers and a variety of different stimuli were carried out on the painted reed frog (Hyperolius marmoratus). These experiments revealed the remarkable ability of very small anurans (<30 mm, SVL) to accurately localize a sound source, in both the horizontal and vertical planes. Furthermore, females were able to discriminate between two sound sources that differed in intensity by only 5 dB and their ability was significantly impaired by the introduction of further sound sources. The confounding effect of multiple sound sources on female choice may explain the presence of nonrandom mating with respect to size in this species. The chorus organization of five species of African anurans was investigated by using playback experiments. These experiments revealed four distinct categories of chorus organization which can be plotted on a continuum, from random calling to very precise triggered responses. The type of chorus organization was found to be directly related to the length of the call and the delay in response to the playback stimulus.