Leafcutter Ant Hitchhiking: The Behavior’s Impact on Forager Velocity and Implications for Foraging Models

Abstract

Leafcutter ant hitchhiking – in which small workers ride on top of leaf fragments that larger foragers carry – is an important part of leafcutter ant foraging, as hitchhikers fulfill several functions while riding on leaves. However, hitchhiker presence also imbalances laden foragers, and thereby slows them considerably. To date, research into these impacts that hitchhikers have on foragers is limited. This thesis, after reviewing the literature on hitchhiking, presents new research on the effects of hitchhikers on forager velocity and efficiency, on both horizontal (the forest floor) and vertical (on the tree) surfaces. The results suggest that foragers especially struggle to maintain balance on vertical surfaces, but that a hitchhiker’s effects on forager velocity are determined more so by the hitchhiker’s behavior than the gradient upon which its transporter travels. At the same time, hitchhikers are found to have minimal effects on transport and provisioning rates – how much leaf material foragers return to the nest per unit time. However, after applying optimal foraging models to the study’s foragers, it was found that leafcutter ants forage at rates far below the proposed definition of optimality. The implications of this discrepancy for leafcutter ant foraging models are discussed, as well as avenues for future research outlined.