Influence of Agricultural Expansion and Human Disturbance on the Encounter Rates of Nocturnal Mammals in Tropical Hill Forests in Bangladesh

Agricultural expansion has had a detrimental effect on tropical forests and the animal communities that depend on them. Agroforestry systems, however, with their more complex tree and plant communities, have been shown to be important habitats for a range of globally threatened species, including nocturnal animals. Here, we present novel data on the encounter rates of seven species of nocturnal mammals in relation to agroforestry systems within four national parks and associated plantations in Bangladesh to examine if encounter rates were influenced by the human population density, presence of plantations, and human access as represented by a Human Influence Index of anthropogenic disturbance. We walked 70.3 km of transects with only semi-natural forest, 26.9 km of transects with semi-natural forest and gardens, and 21.7 km of transects with semi-natural forest and monocultures over 55 nights from 2017-2019. Of the seven species of nocturnal mammals we detected, all were present in Satachari National Park, whereas six occurred in Lawachara National Park, Rajkandi Forest Range, and Rema-Kalenga Wildlife Sanctuary. Within these national parks, three species (Bengal slow loris, large Indian civet, particolored flying squirrel) were more frequently recorded in areas with human disturbance, especially agroforestry plantations. With declining forest cover in Bangladesh, we highlight here the potential of agroforestry systems as emerging important habitats for these species. We encourage long-term studies of these lesser-studied taxa to understand fully the capacity of agroforestry systems in order to support their long-term conservation.

Automated summary

Agricultural expansion has negatively impacted tropical forests and their dependent animal communities. However, agroforestry systems have been found to be important habitats for globally threatened species, including nocturnal animals. This study examined the encounter rates of seven nocturnal mammal species in relation to agroforestry systems in Bangladesh and found that human population density, presence of plantations, and human access influenced the encounter rates. With declining forest cover in Bangladesh, the study highlights the potential of agroforestry systems as crucial habitats for species conservation.