REPRODUCTIVE STRATEGIES IN A FEMALE-BIASED POPULATION OF NATTERJACK TOADS, BUFO-CALAMITA

The behaviour of male and female natterjack toads in an isolated population of about 100 adults in Hampshire, U.K. was investigated over a period of 5 years. Virtually all animals were individually identifiable (by toe-clipping and throat-spot patterns) during the study. Most males remained sexually active throughout the breeding season (April-June) but a significant minority (40-44%) of individuals, indistinguishable by size or survivorship from the population average, visited the ponds only for the first 2 weeks of the breeding seasons. The former group was more successful than the latter in amplexing with females. There was no general correlation between male body size and breeding success. Two distinct and about equally common spatial strategies were evident among breeding males: Residents visited just one pond and called from it throughout the breeding season, while switchers moved irregularly between several ponds. These strategies were highly conserved by individuals between years, and were not related to body size. Switchers were more successful in obtaining females, and did not suffer higher mortality rates than residents. There was a direct correlation between the amount of male calling activity at a pond and its attractiveness to females. In any one year only 44-64% of females spawned. After the breeding season, females spent more time hunting than males during summer and autumn nights. © 1993 The Association for the Study of Animal Behaviour.