Influence of Conspecific Attraction on the Spatial Distribution of Learning Foragers in a Patchy Habitat

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Animal Ecology. Summary 1. Individuals in many social species are attracted to feeding conspecifics. The profitability of conspecific attraction is negatively frequency-dependent and can be modelled as a producer-scrounger (PS) game for which the ESS solution predicts some mixture of producer (no attraction) and scrounger (attraction) tactics in the population. Current models for the spatial distribution of rate-maximizing foragers, which learn the quality of habitats as they exploit patches, ignore the possible effect of conspecific attraction on the stable distribution of foragers. 2. We used simulations of a population with ESS levels of attraction to investigate the effect of conspecific attraction on the spatial distribution of learning foragers which incur travel costs. In habitats where patches depleted slowly, ESS levels of attraction helped foragers which experienced no interference reach the expected ideal free distribution (IFD) by facilitating aggregation to the richest patches. Large aggregations also occurred with interference and thus reduced the fit to the IFD, which in this case predicts a scatter of foragers across patches of varying quality. In habitats where patches depleted rapidly, ESS levels of attraction preventedforagers from reaching the IFD, irrespective of interference levels. Foragers failed to learn habitat quality and thus often aggregated in poor patches, especially in large populations which depleted patches faster and had fewer opportunities to learn quality. 4. Predictions of the model in habitats where patches deplete slowly are supported by several studies. More work is needed for habitats where patches deplete more rapidly. We conclude that conspecific attraction can have important, and often disruptive effects on spatial distributions.When there is no interference between foragers, so that the rate of food intake of an individual is not influenced by the activity of conspecifics, foragers are expected to aggregate in the richest patches. However, as the level of interference increases, some foragers are also expected to occupy patches of lesser quality. If foragers have equal competitive ability, are free to move to all patches, and have perfect knowledge of food availability in the habitat, then at equilibrium the proportion of foragers in a patch should be equal to the proportion of resources in that patch, compensated for the level of interference. At equilibrium, foragers in all patches experience the same intake rate and cannot improve their payoffs by moving to a different patch. The spatial distribution of foragers at

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