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.