A behavior‐based framework for assessing barrier effects to wildlife from vehicle traffic volume

Abstract

Roads, while central to the function of human society, create barriers to animal movement through collisions and habitat fragmentation. Barriers to animal movement affect the evolution and trajectory of populations. Investigators have attempted to use traffic volume, the number of vehicles passing a point on a road segment, to predict effects to wildlife populations approximately linearly and along taxonomic lines; however, taxonomic groupings cannot provide sound predictions because closely related species often respond differently. We assess the role of wildlife behavioral responses to traffic volume as a tool to predict barrier effects from vehicle‐caused mortality and avoidance, to provide an early warning system that recognizes traffic volume as a trigger for mitigation, and to better interpret roadkill data. We propose four categories of behavioral response based on the perceived danger to traffic: Nonresponders, Pausers, Speeders, and Avoiders. Nonresponders attempt to cross highways regardless of traffic volume. Pausers stop in the face of danger so have a low probability of successful crossing when traffic volume increases. Hence, highway barrier effects are primarily due to mortality for Nonresponders and Pausers at high traffic volumes. Speeders run away from danger but are unable to do so successfully as traffic volume increases. At moderate to high volume, Speeders are repelled by traffic danger. Avoiders face lower mortality than other categories because they begin to avoid traffic at relatively low traffic volumes. Hence, avoidance causes barrier effects more than mortality for Speeders and Avoiders even at relatively moderate traffic volumes. By considering a species’ risk‐avoidance response to traffic, managers can make more appropriate and timely decisions to mitigate effects before populations decline or become locally extinct.

Birds and Roads: Reduced Transit for Smaller Species over Roads within an Urban Environment

“…Moreover, Jacobson et al (2016) proposed a species susceptibility to road barrier effects to be related to their ability to recognize and respond to potential predators and threats. "Nonresponders" failed to recognize the threat and crossed irrespective of traffic conditions; "Pausers" stopped in the face of danger; "Speeders" fled in the face of danger; while "Avoiders" were able to recognize traffic as potential predators and began to avoid roads at lower traffic volumes.…”

Roadkill distribution at the wildland‐urban interface

“…High traffic volume may deter observers from being able to make observations in these areas, where driving may take more vigilance or parts of the road and shoulder are more likely to be obstructed from view by other vehicles (Collinson ). Additionally, some species may be deterred from attempting to cross roadways that have high traffic flow and vehicle speed (Jacobson et al ). Overall, we found that the effect of traffic was the least important variable in predicting roadkill presence.…”

Wildlife Deterrent Methods for Railways—An Experimental Study

“…This follows both a similar diurnal pattern to road accidents with most collisions occurring during dusk and dawn, and a similar seasonal pattern with most accidents reported during autumn and winter (Neumann et al 2012;Borda-de-Água et al 2014;Rolandsen 2015). Likewise, as on roads (Seiler and Helldin 2006;Jacobson et al 2016), WTCs were more frequent on railways with intermediate traffic volumes (50-150 trains per day) and less frequent on both calmer and busier tracks.…”