FORAGING BEHAVIOR AND MORPHOLOGY - SEED SELECTION IN THE HARVESTER ANT GENUS, POGONOMYRMEX

Optimally foraging animals can be behaviorally or morphologically adap ted to reduce the energetic and time costs of foraging. We studied the foraging behavior and morphology of three seed harvester ant species. Pogonomyrmex barbatus, P. desertorum, and P. occidentalis, to determi ne the importance of behavioral strategies and morphological features associated with load carriage in reducing the costs of foraging. We fo und that none of five morphological features we measured had a signifi cant impact on seed selection. Also, body size did not influence runni ng speed, an important variable in time costs of foraging. Temperature had the largest effect on running speed in these species. Our results show that these species have foraging strategies which minimize the t ime costs of traveling with seeds. we also describe a patient where th e running speed in individual-foraging species is less affected by inc reasing seed size than in trunk-trail foragers. when temperature and b ody mass are held constant. These results support previous work which showed that lime costs are most important in seed selection for Pogono myrmex, and suggest that central place foraging theory may need to acc ommodate variation in foraging strategy to more accurately predict opt imal seed size selection in harvester ants.