The role of trunk trails in the scouting activity of the leaf-cutting antAtta cephalotes

Abstract

We evaluated the relationship between the trail system and the scouting activity of the leaf-cutting ant Atta cephalotes (L). We counted the number of scout ants in 11 nests at different positions along the trail, before and after tree access was prevented. A. cephalotes tends to search only at limited distances from the end of major trails, suggesting that this leaf-cutting ant employs an area restricted search. We suggest that by scouting mainly at the end of trails, A. cephalotes can concentrate on palatable patches reducing the cost of trail building and minimizing competition with neighboring colonies. This pattern also provides evidence to explain both the conservational grazing and optimal foraging hypotheses postulated for this leaf-cutting ant.Résumé: Nous avons évalué la relation existant entre le système de pistes et les activités de reconnaissance de la fourmi coupe-feuille, Atta cephalotes (L.). Nous avons dénombré les fourmis éclaireuses de 11 nids situés à divers endroits le long d'une piste, avant et après avoir bloqué l'accès aux arbres hôtes. A. cephalotes a tendance à limiter ses recherches près de l'extrémité des pistes principales, suggérant ainsi que cette fourmi coupe-feuille utilise une méthode de recherche à aire restreinte. Nous proposons, qu'en limitant leurs activités de reconnaissance à l'extrémité des pistes, A. cephalotes peut se concentrer sur les îlots de ressources adéquates réduisant ainsi les coûts de construction de pistes et la compétition avec les colonies voisines. Ce patron comportemental est en accord avec les hypothèses de pâturage conservationniste et d'exploitation optimale postulées dans le cas des fourmis coupe-feuille.

Allometric scaling of foraging rate with trail dimensions in leaf-cutting ants

“…Resources conveyed along these transport paths determine the economic activity and ultimate productivity (population growth or economic output) of the societies they serve. Although the geometry of transportation networks is more decentralized in cities than in Atta colonies or organismal vascular systems [30], traffic volume is highly concentrated on a small portion of the total road length in cities [31], much as the traffic of Atta foragers is concentrated on permanent, central trunk trails, while smaller, peripheral trails to particular foraging sites change over time [16,18]. Road length scales below isometry (i.e.…”

“…Instead, they make physical transportation corridors as long as 200 m by cutting and clearing debris and vegetation along paths to foraging sites, and they maintain these pathways in the face of a rain of leaf litter [14]. These trails direct and restrict a colony's searching and foraging effort [15,16], so that essentially all resource movement occurs along these transportation corridors. Trails carry the traffic of workers to and from leaf sources where ants harvest leaf tissue that is used as a substrate for their mutualist fungal gardens in the nest [14,17].…”

Trail Pheromones: An Integrative View of Their Role in Social Insect Colony Organization

“…On their second visit, they use the number of times they cross their own pheromone trail to estimate the area of the nest site (92). Pheromone recruitment to battlegrounds occurs (16,64) during raids on other colonies (65,68) or to avoid competitors and partition territories (42,63,98). Termites, and perhaps ants, may use pheromone trails as templates around which they construct tunnels and galleries (110).…”

Fallen Branches as Part of Leaf‐Cutting Ant Trails: Their Role in Resource Discovery and Leaf Transport Rates inAtta cephalotes

“…Consequently, several ant species preferentially use pathways that are relatively free of debris where their speed can increase when searching for resources and foraging (Fewell 1988, Farji-Brener & Sierra 1998, Denny et al 2001). For instance, ants exploring and carrying resources to the nest through dense vegetation and abundant litter reduce their velocity as the threedimensional distance increases.…”

“…These studies address the performance of workers using trails (Rudolph & Loudon 1986, Burd 1996, the use and design of trails in exploiting resources (Shepherd 1982, Rockwood & Hubbell 1987, Wetterrer 1990, Wirth et al 2003, the cost of trail construction and maintenance (Lugo et al 1973, Howard 2001, and the role of trails in discovering new resources (Shepherd 1982, Therrien & McNeil, 1990, Farji-Brener & Sierra 1998. These studies address the performance of workers using trails (Rudolph & Loudon 1986, Burd 1996, the use and design of trails in exploiting resources (Shepherd 1982, Rockwood & Hubbell 1987, Wetterrer 1990, Wirth et al 2003, the cost of trail construction and maintenance (Lugo et al 1973, Howard 2001, and the role of trails in discovering new resources (Shepherd 1982, Therrien & McNeil, 1990, Farji-Brener & Sierra 1998.…”