Effects of Hunting and Fragmentation on Terrestrial Mammals in the Chiquitano Forests of Bolivia

Abstract

In recently fragmented landscapes, hunting pressure increases because hunters can access previously remote habitats. Yet fewer than 0.5% of fragmentation studies with mammals have also assessed the impacts of hunting. Herein, by means of camera-traps and track-plots, we analyzed the impact of hunting and forest fragmentation on species richness and relative abundances of twelve species of large and mediumsized mammals. With both methods we found fewer species in hunted sites than in control sites, but the effect was inconsistent in fragmented habitats with hunting. Hunting negatively affected the indices of abundance for five of the 12 species and never had a positive effect. Contrary to the hypothesis that the combination of fragmentation and hunting would lead to the largest decrease in abundance, we found that the addition of fragmentation in hunted landscapes negatively affected only two species (red brocket deer [Mazama americana] and margay cat [Leopardus wiedii]) and positively affected three smaller species (crab-eating foxes [Cerdocyon thous], coatis [Nasua nasua], and agoutis [Dasyprocta spp.]). We also found a significant relationship between body mass and the effects of fragmentation (smaller species positively affected), but no relationship between body mass and the effect of hunting. Had we only compared results from the control with fragmented sites, we would have found a negative effect of fragmentation on five species abundance indices, a negative effect on species richness, and a positive effect on three species abundance indices. These results indicate that a failure to explicitly incorporate the effects of hunting into the design of fragmentation experiments can lead to widely different conclusions.Keywords: camera-trap, track-plot, multimodel inference, relative abundance, species richness Resumen En paisajes recientemente fragmentados, la presión de cacería aumenta porque los cazadores pueden acceder a hábitats antes remotos. Sin embargo, menos del 0,5% de los estudios de fragmentación sobre mamíferos ha evaluado también el impacto de la cacería. Por medio de trampas-cámara y parcelas de huellas analizamos los impactos de la cacería y la fragmentación sobre la riqueza y abundancia relativa de doce especies de mamíferos medianos y grandes. Con ambos métodos encontramos menos especies en el sitio bajo cacería, pero el efecto fue inconsistente cuando sumamos la fragmentación. La cacería afectó negativamente los índices de abundancia de 5 de las 12 especies, y nunca tuvo un efecto positivo. Contrario a la hipótesis de que la fragmentación y cacería combinadas llevarían a la mayor disminución de la abundancia, encontramos que la adición de la fragmentación sólo afectó negativamente a dos especies (un venado [Dasyprocta spp.]). Encontramos una relación significativa entre masa corporal y efecto de fragmentación (especies menores afectadas positivamente), pero no entre masa corporal y efecto de la caza. Si hubiéramos comparado sólo los resultados del control y sitios fragmentados, habrí...

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