Road Ecology Center
Wildlife Use of Open and Decommissioned Roads on the Clearwater National Forest, Idaho
- Author(s): Switalski, T. Adam
- Broberg, Len
- Holden, Anna
- et al.
The impacts of roads on wildlife are extensive and can be especially harmful on U.S. National Forest lands where ecosystems are relatively intact. Access allowed by wildland roads can increase poaching, over-hunting, and over-trapping. Roads also increase negative edge effects, cause fragmentation, and facilitate or hinder wildlife movement. Forest Service managers are removing some roads to mitigate these impacts on wildlife, but few studies have addressed the effectiveness of this strategy.
In this study, we tested if wildlife were using decommissioned roads more than adjacent open roads. The study was conducted on the Clearwater National Forest in the Bitterroot Mountains of north-central Idaho where they have removed and revegetated more than 500 mi of roads. From May to October 2006 we monitored wildlife use on open and decommissioned roads using remotely-triggered cameras and baited track plates. Wildlife monitoring was part of a larger citizen monitoring program where a trained volunteer coordinator lead trips into the field each week to collect data on decommissioned roads. Using t-tests, we compared the number of detections and rates of detection between open and decommissioned roads.
Remotely-triggered cameras detected mammals at a higher rate on decommissioned roads than open roads for all species. However, on track plates there were about the same number of detections on open and decommissioned roads. Overall, we could not statistically distinguish the rate of detection between open and closed roads for white-tailed deer, elk, moose, and coyotes. Black bear, however, had a significantly higher rate of detection on removed roads than open roads (p<.01). This finding is consistent with several studies that have found that bears avoid open roads.
While the sample size was small, this study is the first to demonstrate with statistical significance that road decommissioning is restoring habitat for bears. This summer we will increase our sampling efforts to help reduce variability and test if the level of security influences rates of detection. More research is needed to fully understand the effects of road removal on wildlife and their habitat.