  Scale-free foraging patterns are widespread among animals. These may be the
outcome of an optimal searching strategy to find scarce randomly distributed
resources, but a less explored alternative is that this behaviour may result
from the interaction of foraging animals with a particular distribution of
resources. We introduce a simple foraging model where individuals follow mental
maps and choose their displacements according to a maximum efficiency
criterion, in a spatially disordered environment containing many trees with a
heterogeneous size distribution. We show that a particular tree size frequency
distribution induces non-Gaussian movement patterns with multiple spatial
scales (L\'evy walks). These results are consistent with tree size variation
and Spider monkey (Ateles geoffroyi) foraging patterns. We discuss the
consequences that our results may have for the patterns of seed dispersal by
foraging primates.
