Density-dependent foraging in the harvester ant Messor ebeninus: two experiments.

Area of Science:

• Ecology
• Behavioral Ecology
• Entomology

Background:

• Harvester ants are key seed predators in xeric environments.
• Ant foraging behavior significantly influences plant community composition.
• Seed abundance is a primary driver of ant foraging preferences.

Purpose of the Study:

• To investigate how seed density conditioning affects harvester ant (Messor ebeninus) foraging behavior.
• To examine the impact of density on ant recruitment to seed patches.
• To analyze the effect of density on seed selection within patches.

Main Methods:

• Experimentally introduced three seed types (sesame, millet, flax) in varying proportions near Messor ebeninus ant nests.
• Conducted two experiments focusing on recruitment and seed selection stages of foraging.
• Varied seed patch size and composition (single-species vs. mixed-species).

Main Results:

• In small, single-species patches, ants discovered and exploited experimentally common seeds faster than rare seeds.
• This density-dependent effect was more pronounced for less preferred seed types.
• No consistent density effect was observed when seeds were presented in large, mixed patches.

Conclusions:

• Seed density significantly influences harvester ant foraging decisions, particularly in simple patch structures.
• The context of patch composition and size modulates the impact of seed abundance on foraging.
• Findings contribute to understanding ecological interactions between seed predators and plant communities in arid ecosystems.