Roads can have many harmful effects on wildlife. Disturbance from vehicle noise and human activity extends into the nearby habitat, creating a road effect zone characterized by changes in the wildlife community structure and species’ behavior. This can impact conservation efforts designed to reduce the direct impacts of roads, such as wildlife crossing construction. Therefore, to ensure that conservation efforts are effective, we must understand how vehicle traffic impacts the mammal community living around roads. We are working with private landowners in South Texas to assess how traffic volume affects the size of the road effect zone for the mammal community. We set up camera traps in transects along a low-traffic highway (State Highway 186) on the East Foundation’s El Sauz Ranch in Willacy County and along a high-traffic highway (US Highway 77) on a private ranch located in Kenedy County starting in March 2022. We set up cameras using a randomized block design along seven transects set perpendicular to the highway. Seven cameras were set up in each transect, at 200 m intervals, starting 50 m from the highway. We used univariate and multivariate methods to assess how traffic volume and distance from highway affected mammal diversity, richness, and community composition. We have detected ocelot, bobcat, coyote, badger, raccoon, nilgai, white-tailed deer, Virginia opossum, eastern cottontail, javelina, and feral hog on camera traps. Species richness and diversity were greater further from roads, especially on the high-volume highway. Our study will provide information on how carnivores, ungulates, and other mammals use these road effect zones and how vehicle traffic impacts use. By comparing a low-traffic road to a high-traffic road, we will be able to provide key information to private landowners and the Texas Department of Transportation about how changes in traffic volume could impact management practices of working lands around highways and future highway mitigation efforts for ocelots and other mammals.
road effect zone