Predicting the unpredictable: Mammalian responses to fragmentation

Habitat fragmentation is a major cause of species losses. When habitats are anthropogenically fragmented, hunting pressure increases because hunters can more easily access previously remote habitats. This correlation of fragmentation and hunting hinders our ability to understand the impact of each on wildlife within fragmented habitats. As a result, the effects of fragmentation could be inflated or we may fail to find significant synergistic impacts. To disentangle the relative effects of hunting and fragmentation, we studied medium and large mammals within the Chiquitano forests of southeastern Bolivia with camera-traps and track-plots. We found that hunting negatively affected the abundances of seven species and never had a positive effect. Fragmentation negatively impacted two species and positively affected the abundances of four species. Previous research has demonstrated that the effects of hunting and fragmentation on abundances can be predicted by body mass. We found a significant relationship between body mass and the effects of fragmentation (smaller species positively impacted), but the same relationship with hunting was not significant. Thus the abundances of many large mammals declined with hunting, and the addition of fragmentation caused further negative effects on only two species, and had a positive impact on the abundances of smaller mammals. These results indicate that the greatest threat to large and medium mammal survival may be hunting alone.