ASPECTS OF FORAGING DYNAMICS IN COSTA RICAN LEAF-CUTTER ANTS

Krista McDonald, University of North Georgia
Kyle Mobley, University of North Georgia
Paris White, University of North Georgia

Description/Abstract

Leaf-cutter ants (Atta spp.) are eusocial hymenopterans in the neotropics and neosubtropics with a complex caste system. The ants cut leaves from forests surrounding the ant nest and transport leaf fragments back to the nest. There, leaf fragments are processed and provisioned to mutualistic fungi that, in return, provide food to the ants. The leaf-cutter ant worker caste exhibits size polymorphism and is divided into size-based subcastes that perform specific duties. We investigated aspects of foraging behavior in two worker subcastes (small workers, or minims, and larger foragers) in the cloud forest near San Luis, Puntarenas, Costa Rica in late June 2015. Foragers transporting leaf fragments in six foraging columns were captured and their head size and the size of the transported leaf fragment were measured. We also counted the number of minims occasionally riding (hitchhiking) on each transported leaf fragment. Mean leaf fragment wet mass was 3.17x greater than the mean wet mass of the forager transporting the fragment (mean fragment wet mass = 16.4 mg; mean forager wet mass = 5.17 mg), and the surface area of transported leaf fragments increased linearly with increased forager size (F1,176 = 24.2, P = 0.000002). The number of minim hitchhikers on leaf fragments varied from 0-4 ( = 0.5), and the number of hitchhikers increased linearly with increased fragment size (F1,4 = 12.49, P = 0.039). Mean leaf fragment surface area was 52.9 mm2, and foragers transported smaller leaf fragments during windy conditions than in less windy conditions (t = 3.53, df = 175, P = 0.0005). Our results will be compared to those reported previously for leaf-cutter ants in other tropical forests.

 
Mar 25th, 9:00 AM Mar 25th, 10:15 AM

ASPECTS OF FORAGING DYNAMICS IN COSTA RICAN LEAF-CUTTER ANTS

Nesbitt 3217

Leaf-cutter ants (Atta spp.) are eusocial hymenopterans in the neotropics and neosubtropics with a complex caste system. The ants cut leaves from forests surrounding the ant nest and transport leaf fragments back to the nest. There, leaf fragments are processed and provisioned to mutualistic fungi that, in return, provide food to the ants. The leaf-cutter ant worker caste exhibits size polymorphism and is divided into size-based subcastes that perform specific duties. We investigated aspects of foraging behavior in two worker subcastes (small workers, or minims, and larger foragers) in the cloud forest near San Luis, Puntarenas, Costa Rica in late June 2015. Foragers transporting leaf fragments in six foraging columns were captured and their head size and the size of the transported leaf fragment were measured. We also counted the number of minims occasionally riding (hitchhiking) on each transported leaf fragment. Mean leaf fragment wet mass was 3.17x greater than the mean wet mass of the forager transporting the fragment (mean fragment wet mass = 16.4 mg; mean forager wet mass = 5.17 mg), and the surface area of transported leaf fragments increased linearly with increased forager size (F1,176 = 24.2, P = 0.000002). The number of minim hitchhikers on leaf fragments varied from 0-4 ( = 0.5), and the number of hitchhikers increased linearly with increased fragment size (F1,4 = 12.49, P = 0.039). Mean leaf fragment surface area was 52.9 mm2, and foragers transported smaller leaf fragments during windy conditions than in less windy conditions (t = 3.53, df = 175, P = 0.0005). Our results will be compared to those reported previously for leaf-cutter ants in other tropical forests.