Using terrestrial haematophagous leeches to enhance tropical biodiversity monitoring programmes in Bangladesh

1. Measuring mammal biodiversity in tropical rainforests is challenging, and methods that reduce effort while maximizing success are crucial for long-term monitoring programmes. Commonly used methods to assess mammal biodiversity may require substantial sampling effort to be effective. Genetic methods are a new and important sampling tool on the horizon, but obtaining sufficient DNA samples can be a challenge. 2. We evaluated the efficacy of using parasitic leeches Haemadipsa spp., as compared to camera trapping, to sample biodiversity. We collected 200 leeches from four forest patches in northeast Bangladesh, and identified recent vertebrate hosts using Sanger sequencing of the 16S rRNA gene extracted from each individual leech's blood meals. We then compared these data to species data from camera trapping conducted in the same forest patches. 3. Overall, 41.9% of sequenced leeches contained amplifiable non-human mammal DNA. Four days of collecting leeches led to the identification of 12 species, compared to 26 species identified in 1,334 camera trap nights. 4. Synthesis and applications. After assessing the cost, effort and power of each technique, there are pros and cons to both camera trapping and leech blood meal analysis. Camera trapping and leech collection appear to be complementary approaches. When used together, they may provide a more complete monitoring tool for mammal biodiversity in tropical rainforests. Managers should consider adding leech collection to their biodiversity monitoring toolkit, as improved information will allow managers to create more effective conservation programmes.