DENSITY-DEPENDENT FORAGING IN THE HARVESTER ANT MESSOR EBENINUS - 2 EXPERIMENTS

Harvester ants are important seed predators in many xeric environments , and their foraging choices can influence the composition of plant co mmunities. Seed abundance has been cited as an important factor in det ermining such foraging preferences, Three seed types (sesame, millet, and flax) were experimentally introduced in differing proportions near nests of the ant Messor ebeninus near the Dead Sea, in territory admi nistered by the state of Israel. Two experiments were designed to inve stigate the effects of this density conditioning on two stages of the ants' subsequent foraging behavior: recruitment to seed patches and se lection of seeds from within a patch. When seeds were presented in sma ll, single-species patches, experimentally common seeds were discovere d and exploited significantly faster than rare seeds, especially among less preferred seed types. When seeds were presented in large, mixed patches, however, no consistent effect of density was observed.