The effect of anthropogenic disturbance on Attine foraging

Products of the dominant herbivores of Panamanian tropical forests, foraging trails of the leafcutter ant Atta colombica are prevalent at low altitudes. Furthermore, it has been shown that leafcutter ant nest density is higher in anthropogenically disturbed areas than in undisturbed interior habitat, due to the increased colonization effort in the disturbed regions. Although it has not been determined whether the disturbed habitat is beneficial to the leafcutters, it has been suggested that disturbed habitat significantly alters the foraging trail structure for nearby colonies (Vasconcelos et al., 2006). This study outlined basic characteristics of the leafcutter foraging trail structure by mapping 16 mature Atta colombica colonies located in both disturbed and undisturbed habitat. Alterations in foraging trail structure due to disturbance were ascertained by identifying emergent visual patterns as well as by quantitative comparisons and statistics. The majority of observed changes were consistent with the maximization of foraging efficiency by utilizing low-maintenance foraging trails on disturbed surfaces. Additionally, the study proved consistent with the palatable foraging hypothesis, as mature colonies adjacent to roads preferred to forage in the disturbed area where more pioneer species are present. Comparisons of the colonies in undisturbed environments versus disturbed environments concluded that the benefits of increased palatability of plant species and lower costs of foraging trails in disturbed areas outweighed the traditional forces shaping the circular foraging areas in undisturbed areas.