Factors associated with use of wildlife underpasses and importance of long‐term monitoring

Abstract

We evaluated use of 6 wildlife underpasses (UP) using video camera surveillance along State Route 260 in Arizona, USA. We documented wildlife use and compared successful UP crossings by various species and among UP. From 2002 to 2008, we recorded visits by 15,134 animals of 21 species (16 wildlife, 5 domestic) resulting in 72.4% crossing through UP. Elk (Cervus elaphus) accounted for 68% of recorded animals, white-tailed deer (Odocoileus virginianus) and mule deer (O. hemionus) accounted for 13% and 6%, respectively. As elk and white-tailed deer were the only species adequately represented across all UP, we used logistic regression to further evaluate factors associated with successful use of UP. To evaluate habituation over time we limited this analysis to 5 UP monitored for !4 yr. For elk, structural attributes and placement, season, time of day, and months monitored were associated with successful elk UP crossing in year 1, however, by year 4 only structural attributes and placement were significant, suggesting that UP structure and placement likely were of primary importance for successful elk passage. By year 4, probabilities of crossing at 4 of 5 UP converged on >0.70, indicating that given sufficient time to allow habituation, most UP we evaluated appeared to be effective for elk, regardless of structural attributes or placement. For deer, only structural attribute and placement were significant, and aside from one structure did not increase in probability of a successful crossing over time. The overall number of animals and species that crossed SR 260 via UP underscores efficacy of UP in promoting multi-species permeability. Long-term monitoring allows wildlife and highway managers to evaluate adaptation to wildlife crossing structures by different species. Results from this study add to our knowledge of mitigating the impact of highways on wildlife. ß 2011 The Wildlife Society.

Context‐dependent effects on spatial variation in deer‐vehicle collisions

“…These results are consistent with theoretical models that consider how animal body size, movement speed, traffic volume and road width influence DVC (Van Langevelde and Jaarsma 2004). Mitigation measures along roads characterized by high traffic volume should therefore focus on deterring wildlife access to the road surface, i.e., with exclusion fencing (Clevenger et al 2001, Olsson and Widen 2008, McCollister and Van Manen 2010, Gagnon et al 2011.…”

A remarkably quick habituation and high use of a rope bridge by an endangered marsupial, the western ringtail possum

“…Gagnon et al (2011) found that elks (Cervus elaphus) adapted and habituated to terrestrial crossing structures over years, and some factors, such as season, time of the day and length of monitoring, that influenced the crossing frequencies in the first year of monitoring, became insignificant after four years. Given the remarkably quick habituation shown by our study species, we may be able to identify the factors influencing their long term crossing behaviours even in less than four years.…”

“…In previous studies, animals have been observed to show reluctance towards wildlife crossing structures for a certain period of time before they habituated to them and started using them regularly (Gagnon et al 2011). For example, possums and gliders in eastern Australia started using rope bridges after 7 to 17 months of bridge constructions, and the number of crossings increased over time until it reached asymptotes (Weston et al 2011, Goldingay et al 2013, Soanes et al 2013.…”

Effects of Road Density and Pattern on the Conservation of Species and Biodiversity

“…Overall, many studies were in agreement that the effectiveness of crossing structures, fencing, deterrents, and traffic calming measures, was species-specific [96,98,105,121]. A generic "one-size fits all" crossing structure or deterrent does not exist.…”

“…Overall, many studies agreed that crossing structures alone where not as effective as expected [98][99][100][101][102], and those studies that reported road mortality rates more often saw reductions ranging from 10 to 20% [103,104]. Nevertheless, two studies speculated that crossing structures were still biologically effective as low crossing frequencies may be enough to maintain functional connectivity [105,106].…”