Influence of traffic volume on mammal beta diversity within the road effect zone

Disturbance from vehicle noise and human activity extends into nearby habitat, creating a road effect zone characterized by changes in wildlife community structure and species behavior. This can affect conservation efforts along roads, such as wildlife crossing construction. To ensure that conservation efforts are effective, it is important to understand how mammals use road areas. We aimed to assess how traffic volume and distance to highway influenced mammal beta diversity within the road effect zone. We placed camera traps along a low-traffic and high-traffic highway in Texas, USA, between May 2022 to April 2023. We placed camera traps using a randomized block design with transects set perpendicular to the roadway. Starting 50 m from the road, seven camera traps were set at 200 m intervals in each of seven transects. We assessed how traffic volume and distance from road affected mammal beta diversity. We detected nearly all known mammal species larger than rodents (24 species) in the study area, including all known carnivores (10 species). We detected fewer species around the high-volume road, which contributed to a significant difference in beta diversity between the low and high-volume roads. Additionally, community composition tended to be more variable around the high-volume road than the low-volume road. Our study provides insights into the impacts of vehicle traffic on mammal use of road effect zones. Traffic volume is an important indicator of mammal community composition around roads, and road mitigation structures for wildlife will need to account for and mitigate potential effects of traffic volume.