Performance of Arch-Style Road Crossing Structures from Relative Movement Rates of Large Mammals

Abstract

In recent decades, an increasing number of highway construction and reconstruction projects have included mitigation measures aimed at reducing wildlife-vehicle collisions and maintaining habitat connectivity for wildlife. The most effective and robust measures include wildlife fences combined with wildlife underpasses and overpasses. The 39 wildlife crossing structures included along a 90 km stretch of US Highway 93 on the Flathead Indian Reservation in western Montana represent one of the most extensive of such projects. We measured movements of large mammal species at 15 elliptical arch-style wildlife underpasses and adjacent habitat between April and November 2015. We investigated if the movements of large mammals through the underpasses were similar to large mammal movements in the adjacent habitat. Across all structures, large mammals (all species combined) were more likely to move through the structures than pass at a random location in the surrounding habitat. At the species level, white-tailed deer (Odocoileus virginianus) and mule deer (O. hemionus) used the underpasses significantly more than could be expected based on their movement through the surrounding habitat. However, carnivorous species such as, black bear (Ursus americanus) and coyote (Canis latrans) moved through the underpasses in similar numbers compared to the surrounding habitat.

Iran’s roads: mitigating the most serious threat to the critically endangered Asiatic cheetah Acinonyx jubatus venaticus

“…There are many different types of wildlife crossing structures, but of the designs available to them, pumas ( Puma concolor ) appeared to have a preference for open-span bridge underpasses over other types (Gloyne and Clevenger 2001). The location of wildlife crossing structures may, however, be more important than their design (Andis et al 2017). Crossing structures should be constructed where they would have maximum impact, such as at the hotspots identified, or in areas frequently crossed by cheetahs, or along roads that bisect areas with high cheetah utilization, density or occupancy (Smith et al 2015), following best practice guidelines (Trocmé 2015).…”

“…Crossing structures should be constructed where they would have maximum impact, such as at the hotspots identified, or in areas frequently crossed by cheetahs, or along roads that bisect areas with high cheetah utilization, density or occupancy (Smith et al 2015), following best practice guidelines (Trocmé 2015). Crossing structures are commonly used by large carnivores (Grilo et al 2008, Andis et al 2017) so it is reasonable to expect that Asiatic cheetahs will also use them, although confirming this would require monitoring. While wildlife crossing structures are successful at reducing road mortality, they do not keep animals off the road: to achieve this fencing is also required.…”

“…Based on this brief review of potential mitigation strategies we recommend a strategic shift in efforts to reduce road mortality of the Asiatic cheetah. The focus of mitigation should move away from wildlife warning signs, and centre on constructing wildlife crossing structures in conjunction with fencing, as these are likely to be much more effective (Andis et al 2017). It is important to evaluate and monitor the effectiveness of mitigation strategies (Smith and van der Ree 2015).…”

“…If monitoring demonstrated that the initial wildlife crossing structures and fencing were used as anticipated by cheetahs, this scheme could be expanded to a broader scale. Tools such as camera traps or microchip readers could be used to demonstrate their use by multiple individuals, a crucial step in demonstrating their use at a population level (Andis et al 2017; Marnewick et al 2008). Camouflaging and securing camera traps to fixed objects may help to reduce theft, which can be common as poor availability in Iran makes them a target for theft (Parchizadeh 2017a, b).…”

Crossing Corridors: Wildlife Use of Jumpouts and Undercrossings Along a Highway With Wildlife Exclusion Fencing

“…In Southern California, bobcats and coyotes tended to use passages in areas surrounded by less human development (Ng et al 2004). Andis et al (2017) compared large mammal movement between arch-style underpasses and the surrounding habitat. They found that mule deer used the underpasses significantly more, while black bear and coyote were detected as expected based on movement through the surrounding habitat.…”