Efficacy of road removal for restoring wildlife habitat: Black bear in the Northern Rocky Mountains, USA

by T. Adam Switalski and Cara R. Nelson

Abstract

Forest roads reduce habitat quality for wildlife, in part by increasing susceptibility to hunting and poaching.  Road removal is an increasingly common strategy for restoring habitat; however, little is known about responses of wildlife to road removal versus other methods of road closure.  We assessed effects of different types of road closure (gated, barriered, and recontoured) on black bear (Ursus americanus) frequency and habitat on 18 open and closed road pairs in the western USA.  Over four years, 44 bears were photographed during 3545 camera-trap days.  Bear frequency was significantly higher (2.4 vs. 0.6/100 days, respectively) and human frequency was significantly lower (2.4 vs. 361.6/100 days, respectively) on closed than on open roads.  Additionally, abundance of fall foods was higher (23.9 and 12.8%, respectively) and line-of-sight (a measure of habitat security) shorter (54.9 vs. 69.4 m, respectively) on closed compared to open roads.  Bears were detected on closed but not on open roads during daytime, suggesting avoidance of humans.  Among-road-treatment differences included significantly higher frequency of bears on recontoured than on gated or barriered roads (4.6, 1.6, and 0.5/100 days, respectively), and significantly higher cover of fall bear foods on recontoured than on gated or barriered roads (39.3, 12.1 and 16.4%, respectively).  Frequency of bears was negatively correlated with frequency of humans and line-of-sight distance and positively correlated with abundance of fall foods and hiding cover.  Results suggest that while all types of road closure benefit sensitive wildlife, removal by recontour may be the most effective strategy for restoring habitat.