Self-organized asymmetries in ant foraging: a functional response to food type and colony needs

The dominant paradigm to explain asymmetries in the spatial distribution of foraging animals is that they track the spatial heterogeneity of their environment. However, in social insects, endogenous spatial asymmetries can emerge within a uniform environment as an outcome from the self-organizing process of trail recruitment. We studied how self-organized asymmetries contribute to the exploitation of different food sources (carbohydrate or proteins) in colonies of the aphid-tending ant Lasius niger varying in their nutritional needs (presence or absence of brood). Colonies with brood fed on sucrose sources exhibit a higher mobilization of foragers than the other experimental groups. Foraging patterns differ greatly according to food type: colonies strongly focus their activity on only one droplet of sucrose, whereas they show a rather homogeneous distribution of foragers between proteinaceous sources. In addition, the presence of brood in the colony enhances the asymmetry of collective foraging for both types of food. These spatial differences in self-organized foraging patterns allow efficient exploitation of natural resources and play a role in the competitive strategy of this widespread palearctic ant. Copyright 2002.