Leaf Toughness Affects Leaf Harvesting by the Leaf Cutter Ant, Atta cephalotes (L.) (Hymenoptera: Formicidae)

Abstract

Old leaves were found to be nearly four times tougher than younger leaves within a single tree canopy (Rubiaceae) exploited by leaf cutter ants (Atta cephalotes). Ant workers cutting old leaves had significantly greater head capsule widths than those choosing to cut the young leaves; nontheless, the cutting rates for all workers were significantly slower on older leaves. We found no significant preference for young leaves in choice tests using precut leaf disks; this suggests that toughness may be the most important selection criterion in this case. We propose that the differences in cutting rates explain differential harvesting rates of young and old leaves, and that the apparent inability of the majority of workers to cut older leaves would make young leaves more valuable to a nest.