The evolution of spatial memory.

Models of foraging behaviour often assume either that animals are searching for resources, and therefore have no prior knowledge of resource locations, or that they are effectively omniscient, with a comprehensive knowledge of their habitat. By contrast, few attempts have been made to examine the actual conditions under which spatial memory will provide net benefits to foragers. To redress this balance, a model is developed that relates the sensory acuity of the forager and key indices of resource structure to the expected foraging efficiency via calculation of inter-patch distances. Efficiencies of 'ignorant' and 'prescient' foragers are examined in order to derive sets of conditions under which natural selection will favour the evolution of spatial memory capabilities. Results suggest that when resources are densely distributed or sensory acuity is high, spatial memory for resource locations provides no increase in efficiency over that of an 'ignorant' forager encountering resources at random.