Assessing Vertebrate Abundance and the Effects of Anthropogenic Disturbance on Tropical Forest Dynamics

Abstract

The Madre de Dios river basin in southeastern Peru is one of the largest and most diverse forest ecosystems on the planet. Though conservation zones with strict protection do exist in the basin, human population growth and development are having a considerable effect on forest dynamics. One major threat is the hunting-induced reduction or local extinction of large-bodied vertebrates. Vertebrate fauna contribute substantially to the maintenance of biodiversity and ecosystem processes – most notably through the dispersal of seeds by frugivores – and their loss may have disastrous consequences both to forest community composition and to the human populations which rely on ecosystem health and functioning. On the basis of 300km of standardized line-transect sampling, I documented the current densities of vertebrate frugivores across three forest sites under varying degrees of hunting pressure. I compared results across sites and interpreted them in terms of current pressures as well as site-specific trends in seedfall and tree recruitment. Increasing hunting pressure reduced large-bodied frugivores, corresponding with distinct shifts in vertebrate community composition and seedfall patterns. In response to these results, future efforts should promote strict protection of large-bodied vertebrate frugivores, with continued expansive multi-taxa forest monitoring across ontogenetic stages.