At a Crossroads: Impacts of a Major Highway on Mammal Occurrence in a Biodiverse Tropical Forest

Roads strongly impact wildlife movement, spatiotemporal activity patterns, species interactions, and habitat relationships. Roads can thereby affect larger ecological processes, with long‐term consequences for wildlife and ecosystems. We investigated how roads shape mammal behavior, testing two key hypotheses: (1) Mammals avoid areas close to roads due to their sensitivity to traffic, and (2) The impact of roads varies between herbivores and carnivores. We collected mammal occurrence data along a 40‐km‐long National Highway, NH 765, which cuts through Nagarjunasagar‐Srisailam Tiger Reserve, India's largest tiger reserve, and a nearby undisturbed forest trail (Peddarutla Trail) using camera traps. We recorded 16 mammal species, including endangered tigers, leopards, and dholes, using roadside habitats. Contrary to our first hypothesis, our findings revealed that mammal density overall was higher on the NH, largely due to a higher abundance of herbivores. However, carnivore richness was significantly higher on the Peddarutla Trail than on the NH, confirming our second hypothesis that herbivores and carnivores respond differently to roads. When traffic stopped, even elusive and threatened species such as tigers, leopards, and sambar were found to frequent roadsides, clearly indicating that vehicular traffic impedes the movement of mammals. This study provides clear evidence of road avoidance by carnivores and road tolerance by herbivores, and shows how roads can potentially alter mammal behavior. Our results provide first insights into the impacts of roads on mammals within a highly protected tiger reserve in India's Eastern Ghats, and underscore the urgent need for wildlife‐conscious infrastructure planning, as roads increasingly threaten forests worldwide.