Dimensões das trilhas de forrageamento e o tamanho dos ninhos de Atta sexdens (L.) (Hymenoptera: Formicidae)

Abstract

Leaf-cutting ants make foraging trails to collect fresh vegetation, used to cultivate the fungus on which they feed on. Several factors can influence the foraging of these insects and, consequently, their trails, such as weather conditions and colony size. Understanding the relationships between these factors and trails dynamics is important for the ecology and management of this important Neotropical herbivore. The objective of this work was to evaluate the relationships between the dimensions of foraging trails and the size of Atta sexdens nests, during the dry and rainy season. In eucalyptus trees in the Atlantic Forest biome, 60 nests of different sizes were selected and categorized into six size classes, with ten nests each. For each nest, the number and length of chemical and physical trails, width of physical trails, and distance from feeding hole to the nests were obtained. Data were analyzed with gamlss and glmmtmb modeling using R software. The number and length of chemical and physical trails and the width of physical trails used by Atta sexdens increased with the size of their nests, because larger colonies have greater capacity to expand their foraging areas. Atta sexdens used more physical trails than chemical ones. It is known that the use of physical trails increases the foraging capacity, with more leaves being transported in less time. The distance from the feeding hole to the nest and the foraging area increased with the nests size. Larger nests have more workforce to dig longer tunnels, through which they forage with greater safety in relation to desiccation and they are more apt to use a wider trail system. The number and length of trails, the distance from hole to the nest and the foraging area were greater in the dry season, as colonies demand more food in the pre-flight phase and the resources are scarce. Atta sexdens used wider physical trails in the rainy season, as it needs to ensure the efficiency of the search for food at this time of greater rainfall, which reduces foraging time. These results allow us to understand the dynamics in the use of foraging trails by Atta sexdens and the impact of its herbivory on native and commercial vegetation, which can contribute to improving the management strategies of this important herbivore.