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This study focuses on the role of male-male vocal communication in the reproductive repertoire of the South African clawed frog, Xenopus laevis . Six male and two female call types were recorded from native ponds in the environs of Cape Town, South Africa. These include all call types previously recorded in the laboratory as well as one previously unidentified male call: chirping. The amount of calling and the number of call types increased as the breeding season progressed. Laboratory recordings indicated that all six male call types were directed to males; three of these were directed to both sexes and three were directed exclusively to males. Both female call types were directed exclusively to males. The predominant call type, in both field and laboratory recordings, was the male advertisement call. Sexual state affected male vocal behaviour. Male pairs in which at least one male was sexually active (gonadotropin injected) produced all call types, whereas pairs of uninjected males rarely called. Some call types were strongly associated with a specific behaviour and others were not. Clasped males always growled and clasping males typically produced amplectant calls or chirps; males not engaged in clasping most frequently advertised. The amount of advertising produced by one male was profoundly affected by the presence of another male. Pairing two sexually active males resulted in suppression of advertisement calling in one; suppression was released when males were isolated after pairing. Vocal dominance was achieved even in the absence of physical contact (clasping). We suggest that X. laevis males gain a reproductive advantage by competing for advertisement privileges and by vocally suppressing neighbouring males.

The marking of flowers with ephemeral scent is an underappreciated but vital element in the foraging behaviour of social bees. Using observational and experimental data, we tested whether a solitary bee (female Anthophora plumipes) uses scent marking while foraging on flowers of Cerinthe major in Portugal. Females used scent marks with at least two components that differed in their volatility and, furthermore, recognized the marks of different individuals. A very short-term component (<3 min) was attractive, resulting in the observed high level of immediate revisits: this component appeared to be adjusted according to the foraging needs of the moment. A longer-term component (<30 min) was initially repellent and matched the rate of nectar renewal; it, or the response to it, also appeared to be adjusted to the perceived level of nectar reward. There may be even longer-term effects associated with the specific foraging areas of individual bees. Observed differences in the way in which individuals responded to scent marks indicate that they may play a role as part of a dominance or exclusion mechanism among females. Copyright 2001 The Association for the Study of Animal Behaviour.

Copyright 1998 The Association for the Study of Animal Behaviour.