Removal of seeds from vertebrate faeces by ants: effects of seed species and deposition site

Abstract

We investigated the removal of seeds of three species (Philodendron corcovadense and Philodendron appendiculatum (Araceae) and Aechmea sp. (Bromeliaceae)) from the faeces of capuchin monkeys (Cebus apella) by ants in a lowland Atlantic rain forest in southeast Brazil. We examined seed removal by ants in the understory and in treefall gaps, which probably differ greatly in microclimatic conditions. We examined whether seed removal varied among seed species, between understory and gaps, and also among five gaps that differed in size and age. We recorded 17 ant species (4 subfamilies, 9 genera) on the faeces, 8 of which were observed removing seeds. On average, 68% of the seeds had been removed from faecal portions containing 15 seeds each after 24 h. For both the understory versus gap and the among-gap comparisons, seed species significantly affected the proportion of seeds removed, while deposition site (i.e., understory versus gaps or among gaps) had no effect. We interpreted these results as a consequence of the equalizing effect of three myrmicine species (Pheidole sp. 1, Pheidole sp. 3, and Pheidole sp. 7) upon seed removal. These ant species were the most frequently recorded on faeces (63 and 44% in understory and gap sites, respectively, for all three Pheidole species combined) and are among the most abundant litter-foraging ants in the understory and gaps. Because of the high abundance of ants in Neotropical forests, and the flexibility of some ant species in the microclimatic gradient they use, seed removal is likely to be less affected by differences in microclimatic conditions between understory and gaps than by the seed species involved.