Roadside Activity and Behavior of White-Tailed Deer and Other Wildlife near Unfenced Underpasses

More than 1.2 million deer–vehicle collisions (DVCs) occurred in the United States in 2014. U.S. highways have thousands of bridges and culverts large enough to facilitate safe passage of large animals beneath the road. Because these structures were built for drainage or other purposes unrelated to wildlife passage, they are typically spaced miles apart and have no fencing. This study was the first in the United States to evaluate deer activity and behavior at unfenced underpasses and adjoining sections of Interstate roadside. Although black bear activity and other wildlife activity were not a primary focus, they were also evaluated. Thirty-eight cameras were installed beneath a large bridge underpass and a box culvert and along the adjoining 0.5-mi roadside on both sides of the underpass and culvert. There was frequent use of the underpass and culvert by deer to cross the highway (1,187 per year) and high deer activity along the roadside (1,181 per year) despite deer access to the underpass and culvert. A statistically significant relationship was found between roadside deer activity and DVCs. Predominant behaviors were feeding and walking along the roadside, and roadside walking was significantly correlated with DVCs in October and November. Although highway crossing attempts were a low proportion of deer behaviors, crossing attempts resulted in 7.5 DVCs per year on 1-mi highway segments adjacent to the unfenced underpasses. The findings support the installation of fencing along the roadside adjacent to existing large underpasses and culverts used by deer, to mitigate DVCs.