Expanding habitat suitability under changing climate and land use may drive rapid expansion of Russell’s viper (Daboia russelii) in Bangladesh

Eco-climatic and other environmental gradients significantly influence the geographic distribution of reptiles. In Bangladesh, the known range of Russell’s viper ( Daboia russelii ) has expanded extensively in recent decades. Using species distribution modelling, we analysed habitat suitability, dispersal pathways, interspecific competition, and population dynamics to explore the drivers behind this phenomenon. Our findings indicate a five-fold increase in climatically suitable area (76,716 km²) since 2015, attributed to higher cold-season temperatures and increased dry-season precipitation, facilitating the viper’s spread into previously unoccupied regions. The rapid dispersal of these snakes may have benefited from the strong currents of rivers, channels and seasonal waterways, and flat floodplain terrain. Additionally, the extension of agricultural and grassy habitats in new regions has provided abundant rodent prey and minimal predator or competitor pressures, creating ideal conditions for population growth. We also observed a female-biased population structure and large clutch sizes which may have further accelerated reproduction, contributed to rapid population expansion. In rural Bangladesh, where clinicians face multiple problems with the management of Russell’s viper envenoming, increasingly frequent human encounters with this highly dangerous snake have caused great public concern. Despite the observed range expansion, the species also faces challenges such as unsuitable temperature fluctuations, reduced precipitation in some regions, and anthropogenic threats, including anti-snake attitudes and killings. Given the increasing risk of human-snake conflicts, implementing effective snakebite management plans and conservation strategies is crucial to safeguard public health while ensuring the survival of this ecologically and economically important predator of rodents.