SEXUAL SELECTION IN THE LEOPARD TOAD, BUFO-PARDALIS

Sexual selection was investigated in the leopard toad, Bufo pardalis, on the Cape Peninsula in the south-western Cape Province of South Africa. Over three breeding seasons, male mating success was not dependent on either snout-urostyle length (size) or weight, when data were analysed on both a nightly and a seasonal basis. Males did not engage in active searching for females, or attempt to displace other males in amplexus. This is most unusual for an explosive breeder, in which spawning takes place at a specific site. It is suggested that the absence of patterns of behaviour normally adaptive for explosive breeders may be associated with the fact that a congeneric species with a different chromosome number, B. rangeri, overlaps in both distribution and breeding season with B. pardalis over part of its range. Active searching might therefore lead to males finding a mate of the wrong species, which would be maladaptive, as no male was successful in obtaining more than one mating over the three-year study period. Alternatively, the absence of scramble competition in this species may reflect predation pressure.