Foraging Strategies of Ants in Response to Variable Food Density

Abstract

Foraging strategies of three species of desert ants were studied along gradients of altitude and season, both of which affect food density. When food density was low, colonies foraged in long, narrow columns extending linearly outward from the nest entrance. The columns rotated around the nest, and, in time, a circular area was covered. Both the length of the column and the rate of rotation increased with decreasing food density. Under conditions of relatively high food density, the foragers searched for seeds individually, without apparent behavioral cohesion. Each of the three species decreased intraspecific competition by regular spacing of colonies. Interspecific competition was reduced by partially distinct population distributions along the altitudinal gradient. For two species, colonies had a constant foraging area size regardless of altitude or season. For these colonies, time spent searching for food is a good indication of available food. As food density increases, colonies of species with smaller foraging areas become more abundant.