a1 Laboratório de Genética e Biologia Reprodutiva de Plantas, Coordenação de Pesquisas em Botânica, Instituto Nacional de Pesquisas da Amazonia, Caixa Postal 478, Manaus, Amazonas State, Brazil
a2 Norwegian University of Life Sciences, Department of Ecology and Natural Resource Management, P.O. Box 5003, 1432 Ås, Norway
a3 Centre for Ecology, Evolution and Conservation, School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, UK
We know surprisingly little about the fate of seeds of the Brazil nut tree (Bertholletia excelsa) under natural conditions. Here we investigate seed removal, predation and caching of Brazil nuts by scatter-hoarding rodents in the wet and dry seasons, based on an experimental approach using 900 thread-marked seeds. We tracked the fate of seeds handled by these animals to examine how seasonal food availability may influence caching rates, dispersal distances and cache longevity. Most seeds exposed to dispersal trials were removed by scatter-hoarders during the first week in both seasons and seeds were generally buried intact in single-seeded caches within 10 m of seed stations. Seeds were removed significantly faster and buried at greater distances during the dry season. The proportion of seeds buried intact was considerably higher in the wet season (74.4%) than in the dry season (38.2%). Most (99.4%) of the 881 primary caches monitored were recovered, but these had a significantly shorter lifetime in the dry season. Our results show that rodents are highly skilled at retrieving buried Brazil nuts and that caching behaviour appears to be affected by seasonal resource abundance. Reduced seed availability due to intensive harvest could potentially create a dry-season scenario where most seeds succumb to pre-dispersal predation, thereby adversely affecting the natural regeneration of Brazil nut trees.
(Accepted January 06 2010)