Wildlife crossing structures (CS) in combination with wildlife fences are human-created (engineered) features along roads designed to reduce wildlife-vehicle collisions, maintain or restore animal movements, and provide connection between fragmented habitats. In the last decade there has been a growing interest by transportation agencies to implement CS in combination with wildlife fences as a mitigation tool. For decades, research on CS has largely focused on factors affecting the rate of individual species’ passages. However, few studies have looked at a multi-species or community-level response to CS design. Further, after nearly 20 years of research, surprisingly little is known regarding effective monitoring durations and whether passage rates are indicators of population abundance and trends. This gap in knowledge is particularly important in light of the need to perform rigorous evaluations in a time of limited agency budgets and cutbacks in funding.

Crossing structures in Banff National Park and along US Hwy 93 North in Montana, have been monitored for many years, starting as early as 1996, forming the richest database on CS monitoring in the world. These data provide a unique opportunity to assess long-term changes in CS use by a large mammal community. These datasets come from areas with an intact community of large mammals ranging from rare carnivores like wolverine to more common ungulates like white-tailed deer. It is also characterized by mixed landscapes with agriculture and dispersed houses and roads with high traffic volumes. This combination of a relatively intact wildlife community in an area with substantive variation in human disturbance (Banff relatively low human presence and disturbance; Montana relatively high human presence and disturbance) creates a unique ‘reference’ condition to understand how highways and large mammals interact. As large carnivore populations recolonize many parts of their former range, understanding how these species interact with CS in such a reference area will provide critical information to planning mitigation measures in a cost effective and ecologically meaningful manner across North America.

This project is sponsored by a multi-fund pooled study led by the Nevada Department of Transportation.

Using these datasets, the research team will explore the following questions:
1) What is the effect of different covariates on species use over time?
2) What are the effects of design and function of CS on community level metrics?
3) Can CS monitoring (counts) be used as an indicator of population abundance?