Walking through uneven terrains: unraveling worker dynamics in foraging activity

Abstract

During foraging, leaf-cutting ant workers are faced with many challenges in the external environment, such as physical obstacles and uneven terrain, which can hinder their movement and potentially compromise foraging efficiency. The foraging efficiency must be maintained since it is crucial for the development and survival of the colonies. Under this strong selective force, we can expect that the behavioral flexibility of the workers and the mechanism of task allocation will be the tools used to allow them to overcome the difficulties. This study investigated the strategies adopted by Acromyrmex subterraneus workers, focusing on how trail unevenness impacts the workforce allocation, the forager worker velocity, and thus the overall foraging efficiency. We used three 3D-printed foraging trails to simulate different degrees of unevenness on which workers traveled between the colony and foraging arena. We measured the foraging flow, density of workers considering their size classes, occupancy rate (estimated area occupied by a worker), burden, worker speed, and body area ratio of workers (estimated measure of worker leg spreading). Our study demonstrates that trail unevenness significantly influenced worker density, flow, and transport efficiency. Transport efficiency decreased on more uneven trails due to reduced worker speed rather than load adjustments, suggesting that workers carried optimal loads but had to modify their stride to walk a higher unevennes surface trail. These findings highlight how physical trail conditions impact foraging coordination, emphasizing the importance of well-maintained foraging trails for optimizing worker efficiency.