Document: ANT-3-83-12

Factors affecting the permeability of wildlife passages in Banff National Park, Alberta, Canada.

WALTHO, N.* ¹, A.P.CLEVENGER ², K.GUNSON ³ and B.CHRUSZCZ ³

York University, York, Ontario, M3J 1P3, Canada ¹
University of Calgary, Calgary, Alberta, T2N 1N4, Canada ²
Parks Canada, Banff, Alberta, T0L 0C0, Canada ³

Abstract:
Mitigation passages such as wildlife overpasses and underpasses have been designed to perforate road barriers and maintain horizontal natural processes across the landscape. Nonetheless, few studies attest the efficacy of these structures and of those studies all were limited to single species analyses. No study considers the effectiveness of wildlife overpasses and underpasses at multi-species scales equitable to the large mammal community or as a function of time in operation. Species performance ratios (i.e., observed crossing frequency / expected crossing frequency) were evaluated for four large carnivore and two ungulate species to mitigation structures in Banff National Park, Alberta, Canada. Observed crossing frequencies were collected from year-round passage monitoring. Expected frequencies were developed from independent models based on data from radiotelemetry, pellet counts, and habitat suitability indices. A null model was tested to determine whether wildlife crossing structures serve species equally, or whether such structures limit habitat connectivity across roads in species-specific ways. In a two-tiered analysis, we first modeled species responses to 15 variables associated with 11, 12-year old structures. Variables encompassed mitigation structure, landscape features, and human activity attributes. In the second tier, we conducted a broader scale analysis that included an additional 12, 2-year old structures. The null model showed that species responded to structures differently. The first analysis showed that at the older structures, levels of human activity consistently ranked high as a significant factor affecting crossings for individual species, species groups, and large mammal community. Carnivores avoided structures close to town or with high levels of human activity and preferred structures close to major drainages. For ungulates the structural attributes were more important than human ones. When the newer structures were included in the analysis the time in operation was the strongest factor determining passage and was positively correlated. Our results suggest that individuals require time to adapt to mitigation structures and only once this has occurred, evaluations can be carried out to identify the factors influencing passage rates.

Keywords: Banff National Park, Large carnivores, Mitigation, Permeability, Wildlife passages, Ungulates

This abstract is being presented at: 4:30 PM in session:
Oral Session #51: Disturbance Ecology: Harvesting, Grazing and Roads.