Safe Passage

The I-40 Pigeon River Gorge Wildlife Crossing Project

research

Research results unveiled for Safe Passage project area, providing framework for wildlife–vehicle collision prevention

The burden imposed by I-40 on wildlife habitat connectivity and transportation safety makes the Pigeon River Gorge a national priority site for wildlife–vehicle collision mitigation.

On June 29, two partners of the Safe Passage Fund Coalition — Wildlands Network and the National Parks Conservation Association — released their official report, Road Ecology Research and Mitigation Strategies to Improve Wildlife Connectivity and Human Safety along I-40 in the Pigeon River Gorge.

The much-anticipated report details the findings of more than three years of roadside research in the I-40 Pigeon River Gorge project area combined with analysis of 20 years of historical data. The study was one of largest road ecology research projects ever completed in the eastern United States.

The report was authored by a team of cooperating researchers and scientists:

  • Liz Hillard – Ph.D., Senior Wildlife Biologist, Wildlands Network
  • Steve Goodman – Conservation Biologist, National Parks Conservation Association
  • Ron Sutherland – Ph.D., Chief Scientist, Wildlands Network
  • Jeff Hunter – Southeast Regional Program Manager, National Parks Conservation Association

Based on the research findings, the report provides 20 detailed mitigation recommendations for improvements to existing structures or creation of new structures throughout the Gorge, and calls for installation of a system of strategically placed wildlife fencing. Additionally, through consensus, the report’s authors provide seven “top priority” recommendations, including key opportunities to construct wildlife overpasses and install larger culverts under the highway.

Click here to read the executive summary of the report, and click here to read the report in full.

READ THE SUMMARY

The research provides the framework for mitigation strategies to both improve existing structures and construct new wildlife-specific structures to reduce wildlife–vehicle collisions (WVCs) and increase wildlife habitat connectivity.

Science Blog: Do animals behave differently around busy roadways? Yes, observation shows.

Observations in the Safe Passage study area and beyond have begun to show that wild animals are keenly aware of the threats associated with roadways.

Safe Passage researchers have observed what appears to be heightened bear vigilance near the highway (see Figures 1A-1C). Researchers in other parts of the country have shown that GPS-collared black bears approaching roads, especially high-volume highways experience increased heart rates (Ditmer et al. 2018) and higher movement speeds (Zeller et al. 2020). 

Roads sometimes serve as barriers and, other times, as mortality traps. It is an ongoing practice in risk/reward evaluation — for food needs, breeding opportunities, etc. — that bears and other wildlife must make when traversing landscapes infused with roads.

Bears observe and approach Interstate 40 with caution

Figure 1A. An adult black bear observing Interstate 40 one hundred feet away.
Figure 1A. An adult black bear observing Interstate 40, from 100 feet away.
Figure 1B. A young black bear observing Interstate 40 one hundred feet away.
Figure 1B. A young black bear observing Interstate 40, from 100 feet away.
Figure 1C. Bear approaching and returning from Interstate 40 seventy feet to the right.
Figure 1C. Bear approaching and returning from Interstate 40, from 70 feet to the right.

Though data collection is not complete, near the highway, Safe Passage has so far observed fewer sows with cubs, fewer sibling-and-adult interactions and fewer of other normal behaviors. This sharply contrasts with observations made at a distance from the highway, where less stressful and less human-disturbed environments show bears being bears — playing or showing aggression, climbing trees and marking surroundings with their scent (see Figures 2A-2C). 

Farther from the highway, bears relax and play

Figure 2A. Bears wrestling in Great Smoky Mountains National Park two miles from Interstate 40.
Figure 2A. Bears wrestling in Great Smoky Mountains National Park two miles from Interstate 40.
Figure 2B. Adult male black bear sitting just before dusk 700 feet from Interstate 40.
Figure 2B. Adult male black bear sitting just before dusk 700 feet from Interstate 40.
Figure 2C. Juvenile black bear climbing tree 1000 feet from Interstate 40.
Figure 2C. Juvenile black bear climbing tree 1000 feet from Interstate 40.