Cognitive abilities of a central place forager interact with prey spatial aggregation in their effect on intake rate

When foraging in a landscape, predators choose travelling directions according to their immediate knowledge of prey distribution within their perceptual fields and, when appropriate, to their past foraging experience. A substantial part of foraging theory is based on patch use in spatially implicit domains, and rarely has it considered foraging paths involving directional choices driven by memory and perception. Using a model mixing directed and random movements of a predator, we investigated how perception range and duration of spatial memory influence the long-term intake rate of a central place forager depending on prey spatial distribution. We found that intake rate increased and eventually saturated with increasing perception range regardless of prey spatial distribution. In contrast, the effect of spatial memory duration was mediated by the level of prey spatial aggregation. Assuming that an increase in memory or perception abilities has a cost, we found that it was not beneficial to possess simultaneously a wide perception range and a long-term spatial memory when prey distribution was aggregated. Moreover, when looking at the functional response of predators with different 'cognitive strategies', we found that those relying mainly on memory were limited by the prey global densities while those relying mainly on perception were limited by the level of prey aggregation. These results suggest that cognitive strategies might have evolved as a response to the prey spatial distribution and that prey spatial aggregation, not only prey global density, should be considered an important component of the functional response. (C) 2009 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.