Long-term field study of the behaviour of Xenopus laevis (Pipidae) in a small dam

ABSTRACT A study of the behaviour of Xenopus laevis in a small dam in South Africa was continued annually from 1992 until 1999. All individuals were tagged. The annual number of frogs varied between 22 and 109 by migration. The sex ratio remained balanced. Most subadults stayed for just one season, whereas half of the adults remained longer. Some individuals reappeared after one or more years of absence. Within a season, male activity was concentrated in series of nights between quiet periods. Higher population density did not result in more territorial, stationary, or roaming males, or more fighting, but mainly in a higher number of inactive males. Fighting was intense, however, at extreme low water in 1995. Territorial males might maintain their territory in subsequent years. The size of individuals did not differ between behavioural types and males of any behaviour could mate successfully. The rare matings aggregated in adjacent nights at peak calling. Female approach to males was not seen, but playback in silent nights caused some females to linger near the loudspeaker. Females that experienced no amplexus during our observations were found significantly more in the shallow areas of the dam where sound did not enter. For mating, females accepted only males larger than 65 mm SVL and repelled all smaller ones. Mating was not size assortative. In both sexes, maturation took years of gradual development before successful mating.