Mammal richness and diversity in a Himalayan hotspot: the role of protected areas in conserving Bhutan's mammals

More than 51% of Bhutan is in a protected area (PA) network and our study demonstrates its effectiveness in conserving large and medium mammal species. We conducted camera trapping in Bhutan’s PAs, biological corridors (BCs) and intervening non-protected areas (NPAs) to investigate the richness and diversity of mammals, and assess the network’s efficacy in protecting mammals. 1858 camera traps were deployed within 1129 5-km × 5-km grids over 536 days between 2014 and 2015, resulting in 148,598 trap-nights (mean = 80 traps-nights/camera) which yielded nearly 10 million photos (mean = 5368 photos/camera trap). Fifty-six mammal species (65% of Bhutan’s 86 medium and large terrestrial mammal species) representing 18 families within seven orders were identified, of which, 18 (32.16%) are listed as threatened by the International Union for Conservation of Nature. There was a significant difference in mammal diversity between PAs, BCs, and NPAs (PERMANOVA test; p < 0.001; Pseudo-F = 6.40; unique perms = 9921), with the strongest difference between PAs and NPAs. Additionally, Hill’s numbers q = 0 (species richness), q = 1 (Shannon’s entropy index) and q = 2 (Simpson’s concentration index) revealed a higher mammal diversity in PAs compared to BCs and NPAs. Higher mammal diversity in PAs can be attributed to the added presence of threatened species, including the tiger Panthera tigris, red panda Ailurus fulgens, Asian elephant Elephas maximus, and golden langur Trachypithecus geei. However, BCs and NPAs share similar patterns of mammal diversity, and globally threatened species such as the Chinese pangolin Manis pentadactyla and Indian pangolin Manis crassicaudata were only detected in NPAs. Although Bhutan’s PA network is effective in conserving much of the country’s mammal diversity, realignment of some protected areas and biological corridors would ensure the long-term protection of several threatened mammal species.