Small rodents as significant dispersers of tree seeds in a Neotropical forest

Through seed dispersal and predation, terrestrial mammals should be an important component of the mechanisms that determine patterns of tree recruitment in tropical forests. Despite their great abundance and ubiquity in Neotropical forests, small rodents as seed predators and dispersers remain largely forgotten. To investigate the fates of seeds in a hunted primary forest in Belize, we tagged seeds of Astrocaryum mexicanum (Palmae), Ampelocera hottlei (Ulmaceae), and Pouteria sapota (Sapotaceae) and placed them into open plots, exclosures accessible only to small mammals, and exclosures accessible to medium-sized and small mammals. The exclosure experiments and fates of the seeds show that the spiny pocket mouse, Heteromys desmarestianus (Heteromyidae), was the dominant handler of seeds of the first two species and also removed a significant proportion of the very large-seeded Pouteria. Most of the seeds were killed immediately upon removal, but many of the seeds (3 - 18 %) of the first two species were scatterhoarded (dispersed and buried in the soil) by Heteromys. Some of the scatterhoarded seeds (29 %) remain buried and therefore protected from predation by other animals. Agoutis (Dasyprocta punctata), a caviomorph rodent, buried 13 % of the seeds of Pouteria, and Heteromys consumed and dispersed but did not bury Pouteria seeds. Results of this study support predictions by some researchers that small rodents are dominant terrestrial granivores in Neotropical forests. The role of small rodents as seed dispersers, however, has never been fully appreciated.