Crossing structures reconnect federally endangered flying squirrel populations divided for 20 years by road barrier

Abstract

In the Unicoi Mountains of southwestern North Carolina, USA, a 2 lane scenic byway created a barrier to dispersal for the federally endangered Carolina northern flying squirrel (Glaucomys sabrinus coloratus). Unable to glide across the road, squirrels in the divided subpopulations faced reduced access to mates, den sites, and foraging grounds. We installed 3 pairs of modified wooden utility poles as crossing structures to enable gliding over the road in both directions. Using wildlife cameras, we monitored use of the crossing poles by northern flying squirrels for 15 months. Additionally, we tracked movements of 4 radiocollared northern flying squirrels between habitat patches and checked nest boxes for evidence of squirrels crossing the road. Cameras recorded 5 still images and 25 videos of northern flying squirrels on the crossing poles, with flying squirrels leaping across the road in 56% of videos. Crossings increased from 0 crossings in a previous study to 14 crossings in this study. For the first time since crossing-pole installation, squirrels used dens on the opposite side of the road from where they were initially captured and tagged. We believe that these structure-assisted road crossings in the Unicois are the first observed in a North American gliding mammal. Although northern flying squirrels used crossing poles to glide over a rural, low traffic, 2-lane road, further research should be conducted to determine whether this technique is applicable to different road types and other types of linear barriers in North America. © 2013 The Wildlife Society.