Road Ecology Center

We used integrated, four-camera video surveillance systems to assess and compare wildlife use of five openspan bridged wildlife underpasses along a 30-km stretch of reconstructed highway in central Arizona. We determined passage rates (proportion of animals approaching and crossing through underpasses) and categorized behavioral responses exhibited during underpass approaches and crossings. Two underpasses have been monitored for over 2-1/2 years; both open into the same meadow/riparian complex, are only 225 m apart, but have different below-span characteristics and dimensions, providing an excellent opportunity to compare use by wildlife. Four underpasses, in place for 18 months, have been monitored for over one year; two of these allowed for monitoring before ungulate-proof fencing was erected in association with the underpasses. This allowed us to record pre- and post-fencing passage rates and behavior to assess the role of fencing in funneling animals to underpasses and influencing passage rates. At the two adjacent underpasses monitored over 2-1/2 years (December 2002-June 2005), we recorded eight species of wildlife totaling 3,914 animals, including 3,548 elk (Cervus elaphus nelsoni), 216 white-tailed deer (Odocoileus virginianus cousei), and 6 species of carnivores including 4 mountain lions (Puma concolor). Overall, elk passage rates averaged 0.62, while only 15 deer crossed the underpasses (0.075 passage rate). We detected significant differences in passage rate and behaviors indicative of resistance to crossing. One underpass with earthen 2:1 sloped sides has been used more by elk (1,908 elk) displaying less resistant behaviors and delay in crossing compared to one with concrete walls (598 elk). This information was used in an adaptive management context to minimize concrete walls and pursue alternatives to soil stabilization at a wildlife underpass currently under construction. At the three recently completed underpasses, monitored February 2004-June 2005, we recorded 10 species of wildlife totaling 1,703 animals, including 860 elk, 367 white-tailed deer, 194 mule deer (O. hemionus), and 7 species of carnivores. Elk passage rates to date averaged 0.35, with the passage rate at two underpasses exceeding 0.50 and two below 0.27. Both white-tailed and mule deer regularly used the newer underpasses with passage rates of 0.40 and 0.29, respectively. Ungulate-proof fencing was completed through the underpasses in December 2004, and we continue to monitor wildlife response and changes in passage rates since this fencing was erected. Video surveillance constitutes a valuable tool in quantifying wildlife use of underpasses and assessing the effectiveness of underpasses and fencing. Continued monitoring will allow us to assess long-term use of passage structure.