Socially stable territories: The negotiation of space by interacting foragers

This article presents a theory of territoriality that integrates optimal foraging and conflict resolution through negotiation. Using a spatially explicit model of a sit-and-wait forager, we show that when resources are scarce, there is a conflict between foragers: there is not enough space for all individuals to have optimal home ranges. We propose that a division of space that solves this conflict over resources is the outcome of a negotiation between foragers. We name this outcome the socially stable territories (SST). Using game theory we show that in a homogenous patch occupied by two interacting foragers, both individuals receive identical energy yields at the socially stable territories; that is, there is economic equity. Economic inequity can arise in a heterogeneous patch or from asymmetries in fighting abilities between the foragers. Opportunity costs play a role in reducing economic inequity. When the asymmetry in fighting abilities is very large, a negotiated division of space is not possible and the forager with lowest fighting ability may be evicted from the habitat patch. A comparison between territories and overlapping home ranges shows that energy yields from territories are generally higher. We discuss why there are instances in which individuals nevertheless overlap home ranges.