The impact of lekking on the spatial variation in payoffs to resource-defending topi bulls, Damaliscus lunatus

In mating systems research it is often ignored that the spatial relationship between individuals adopting alternative mating tactics may influence the intensity of their interactions and therefore also their tactical payoffs. I here take a novel approach to investigating the coexistence of lek territoriality and resource territoriality in male topi antelopes by including territorial distance from a lek centre as a continuous variable. Using the body size of territory holders as a proxy for territorial payoffs, I show that the attractive force of lek centres impact negatively on payoffs from surrounding territories only within an 1800 m radius. Thus, lek males are significantly larger than resource defenders inside, but not outside, this impact zone. The impact zones encompass the ranges during oestrus of 91% of the females mating on leks, and because female topi are highly promiscuous, the impact zone corresponds roughly to the area within which resource territorial males experience sperm competition with lek males. These results can be explained by a preference of oestrous females for mating with central males inside, but not outside, the 1800 m zone. The study illustrates how taking spatiality into account can reveal significant differences in tactical payoffs within behavioural categories that are traditionally regarded as uniform. (c) 2007 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.