Foraging Ecology of the Leaf-Cutter Ant, Acromyrmex subterraneus (Hymenoptera: Formicidae), in a Neotropical Cerrado Savanna

Abstract

AbstractFungus-farming ants cultivate a fungal symbiont inside the nest that serves as a food source. Leaf-cutter ants are distinctive among fungus-farmers because they forage for fresh plant material to nurture the fungus. Here we investigate the foraging ecology of Acromyrmex subterraneus (Forel) in the Brazilian cerrado savanna. We examined the species activity pattern, forage material collected, and the relationship between load mass and forager size. Ant activity peaked at night and was negatively related to temperature but positively related to relative air humidity. The majority of the items collected by ants was plant material: dry and fresh leaves, flowers, and fruits. Trunk trails ranged from 0.7 to 13 m and colony home ranged from 2 to 28 m2, indicating that ants collect material nearby the nest. Total load mass was positively associated with forager size, especially in the case of leaves. The negative relationship between ant size and burden suggests that ants might optimize their delivery rate by collecting lighter substrates more frequently. Given their pest status, most studies on leaf-cutters are undertaken in human-altered environments. Information on A. subterraneus in native cerrado is imperative given the threatened status of this vegetation. Leaf-cutters thrive in disturbed cerrado and severe seedling herbivory may hinder vegetation recovery. Our fieldwork may provide insights for management techniques of Acromyrmex colonies in agroecosystems, as well as for restoration programs of degraded cerrado areas.