Road mitigation is a demographic filter for grizzly bears

Abstract

Crossing structures (i.e., underpasses and overpasses) are becoming a widespread approach to promote movement of wildlife across roads. Studies have shown that species select for different crossing structure designs, yet little is known about intraspecific variation (i.e., differences among demographic classes) in crossing structure preference. Using data on grizzly bear (Ursus arctos) movement in Banff National Park (AB, Canada), we focused on selection by family groups (adult females travelling with young) and singleton (adult male or female) bears for 5 crossing structure designs distributed among 44 sites. Using data from the world's longest running monitoring program (1997-2014) on wildlife crossing structure use, we created an economic model to estimate demographic-specific cost-effectiveness for each crossing structure design. We found that all grizzly bears selected larger and more open structures (overpasses and open-span bridges). Use of these structures has generally increased with time at a rate that exceeds estimates of population growth. Family groups were more selective than singletons and strongly selected overpasses. In spite of singletons' selection for overpasses and open-span bridges, box culverts were comparable in costeffectiveness. Our results suggest that structure designs targeting the selection of grizzly bear family groups are effective at restoring population connectivity, but a systematic approach to designing highway mitigation also would consider the role of lesser used structures in reducing intraspecific predation and multispecies connectivity targets. Ó 2017 The Wildlife Society.

Wildlife mortality on roads and railways following highway mitigation

“…, ) that simultaneously examine multiple species and demographic classes of predators and prey (Ford et al. ), for which changes in abundance are also assessed (Teixeira et al. ).…”

“…If wildlife managers are to meet the challenges of expanding global transportation networks, which are projected to be 60% higher by 2050 (Dulac 2013), they will need more studies that address the multi-faceted complexity of transportation mitigation. These studies must pair accurate reporting of collisions (Child et al 1991) with powerful BACI (before-after-controlimpact) designs (van der Grift et al 2013, Rytwinski et al 2015) that simultaneously examine multiple species and demographic classes of predators and prey (Ford et al 2017), for which changes in abundance are also assessed (Teixeira et al 2017). Railways must reach the level of study, understanding, and mitigation that has long been applied to roads (Dorsey et al 2015, Popp andBoyle 2017).…”

Genetic tagging in the Anthropocene: scaling ecology from alleles to ecosystems

“…The use of family triads (or limited pedigrees) is an emerging direct genetic method that overcomes the inability to detect dispersers in well-mixed populations and allows the identification of both apparent and realized connectivity (Cosgrove et al 2017, Cayuela et al 2018see Proctor et al 2018a for an example). The use of family triads in connectivity studies will ultimately provide insight into the assumed link between apparent and realized connectivity (Cayuela et al 2018), and perhaps more importantly, the efficacy of mitigation efforts (Sawaya et al 2014), like sex-specific wildlife crossing structures across highways (Ford et al 2017).…”

The Use of Fiber-Reinforced Polymers in Wildlife Crossing Infrastructure

“…Since FRP bridges are corrosion resistant and hold their structural properties over time, owners of the bridge can benefit by reducing costly and time-consuming maintenance over its lifetime. Adapting FRP bridges for use as wildlife crossing structures can contribute to the long-term goals of improving motorist and passenger safety, conserving wildlife and increasing cost efficiency, while at the same time reducing plastics in landfills.Sustainability 2020, 12, 1557 2 of 15 connectivity for particular species [8]. Although usually more expensive than underpasses [3], overpasses are also frequently chosen by some species [9].The length and the width of overpasses continue to challenge engineers, architects and ecologists.…”

“…Sustainability 2020, 12, 1557 2 of 15 connectivity for particular species [8]. Although usually more expensive than underpasses [3], overpasses are also frequently chosen by some species [9].…”