Mammal depletion processes in a UNESCO biosphere reserve: an integrative analysis of population viability

Abstract Many tropical biosphere reserves face the problem of overexploiting biological resources, which is a major cause of biodiversity loss. We used an integrative approach, combining camera trapping and bat trapping in diverse habitats over multiple surveys in Yangambi Biosphere Reserve, Democratic Republic of the Congo. We investigated whether species-level traits of volant and nonvolant mammals, as well as key features of their habitats, can predict effects on species detectability and occupancy, and thus on community-level species richness. We applied single-season occupancy models using multi-species data for camera trap and bat trap datasets. We found a positive effect of denser woodlands on occupancy estimates over 6480 camera-days. Average adult body weight and whether species were group-living negatively influenced species detection estimates. Species richness and body size assemblages approximated marginal rainforest diversity. This included small-bodied, generally high-hunting-resilient arboreal and terrestrial species. During 324 trap-nights, site location was the main determinant of habitat occupancy at the community level. Occupancy estimates were not, however, directly linked to variables measured in different stands. This may be a consequence of habitat patterns at larger spatial scales, which require additional data to clarify. Species-level characteristics that might influence detection estimates were not, however, included in the parsimonious output of the model used. Our findings indicate specific mechanisms triggering mammalian impoverishment above a critical size that may drive ecological changes. Thanks to certain life-history traits, bats can compensate for some of the lost services previously provided by large mammals, thus contributing to the maintenance of biodiversity dynamics.