An Evaluation of Roadside Activity and Behavior of Deer and Black Bear to Determine Mitigation Strategies for Animal-Vehicle Collisions

About the report:

Virginia is consistently among the top 10 states with the highest number of deer-vehicle collisions (DVCs), with more than 56,000 DVCs per year since 2007. The Virginia Department of Transportation has targeted a section of I-64 on and near Afton Mountain for safety and mobility improvements because of a high number of crashes and traffic stoppages. DVCs are a primary driver safety concern in the area, and vehicle collisions with black bears are also relatively frequent. Mitigation strategies are needed to address this issue.

The purpose of this study was to evaluate white-tailed deer activity and behavior along (1) an interstate roadside adjacent to unfenced isolated underpasses used by deer and (2) a stream corridor / highway intersection with no viable underpass for deer. Although not a primary focus, black bear and other wildlife activity was also evaluated. Two years of camera data and animal carcass removal data were analyzed to gain a better understanding of deer and black bear activity and behavior relative to the two road and landscape features.

Cameras were installed at a large bridge underpass and a box culvert (both used by deer to cross beneath the highway) and along the adjoining 0.5-mile roadside on both sides of the underpasses. Despite frequent use of the underpasses by deer (1,187 per year), there was high deer activity along the adjacent roadside (1,182 per year). A statistically significant relationship was found between roadside deer activity and DVCs (i.e., as deer activity increased, DVCs increased), and this relationship was strongest in October and November.

Although highway crossing attempts comprised a low proportion of deer behavioral responses (n = 100 crossing attempts), crossing attempts resulted in 7.5 DVCs per year on the 1-mile highway segments adjacent to each unfenced underpass. Deer along the roadside exhibited relatively low responsiveness (or vigilance) to the interstate; predominant behaviors included walking along the roadside and feeding. At the stream corridor / highway intersection, cameras were installed at the intersection and extended along the adjoining 0.25-mile roadside on both sides of the intersection. Bear were more active along the roadside near the stream corridor than at the underpass sites.

The stream corridor and associated topography were found to concentrate deer movement toward a relatively short section of highway; deer activity was statistically higher nearest the stream corridor / highway intersection and decreased farther away from this intersection. DVCs were statistically correlated with roadside deer activity and were significantly higher during October and November than during the other months of the year.

Study recommendations include (1) the installation of fencing along the roadside adjacent to existing large underpasses, and (2) an animal advisory message on the dynamic message signs along I-64 in the Afton Mountain area. Messages should be displayed from dusk through dawn from October through November (to correspond with periods of higher deer activity and DVCs). Fencing both sides of just one underpass is expected to result in a savings in costs associated with DVCs of $501,473 over its service life. A planned post-mitigation study may find that these low-cost forms of mitigation could have a substantial impact on drivers and wildlife, particularly if implemented on a larger scale.

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