Visual displays in a nocturnal rhacophorid frog (Buergeria japonica)

Abstract

Abstract We report a visual display, leg-stretching, in the nocturnal Ryukyu Kajika frog (Buergeria japonica) on Iriomote Island in southern Okinawa, Japan. This visual display is produced by males before, during, or after a vocalization and involves the extension of one or both hindlimbs outwards at substrate level. Leg-stretches in this species are performed during male-male agonistic interactions in choruses, and almost exclusively in concert with aggressive vocalizations. These observations are one of the first reports of visual displays for the Rhacophoridae family and provide insights into why visual displays evolve in frogs, especially in nocturnal species. We discuss our observations in the context of underlying mechanisms and selective pressures driving the evolution of anuran visual displays.