Management of carnivores in the Western United States is an important conservation objective. Several carnivores, such as Canada lynx, grizzly bear, Mexican gray wolf, Northern Rocky Mountain wolf, jaguar, San Joaquin kit fox, and ocelot are listed under the Endangered Species Act. Others such as wolverine, American marten, swift fox, and fisher receive special status due to rarity or conservation concerns. Even relatively common carnivores such as black bear, mountain lion, bobcat, coyotes, and raccoons are of great interest and concern to the public.

Carnivore populations exhibit several traits that can render them particularly vulnerable to habitat fragmentation and highway impacts. Because of the their large home-range sizes, carnivores often have to cross one or more highways to fulfill their food or water requirements, find mates, or disperse into unoccupied habitats. Carnivore populations can be at risk when mortality rates rise because of their low population densities and reproductive rates.

Highways are one of several important components to consider when managing carnivores and other wildlife species. Highways often result in serious unintended impacts such as direct and indirect losses of habitat, habitat fragmentation, population fragmentation, and increased mortality of wildlife and humans. Over the last twenty years, highway departments, land management agencies and wildlife agencies have worked together to develop management practices that reduce impacts to carnivores and other wildlife species. Simultaneously, research is increasingly available to assist agencies and the public in understanding how to reduce the impacts highways have on wildlife. This research has been directly applied to improve highway safety and mitigation through wildlife habitat linkage analysis, development of effective wildlife and fish crossing structures, fencing, and land purchase or conservation easements, to protect important wildlife habitats.

Growing scientific research shows the importance of wildlife crossings and restoring wildlife habitat connectivity. In Banff National Park, a series of 22 underpasses and two overpasses, tied together with fencing, have decreased total roadkills by 80 percent. Monitoring has documented approximately 75,000 crossings of wildlife using these structures including wolf, grizzly bear, elk, lynx, mountain lion, and moose. It is also known that large, interconnected wildlife populations are more “viable” or “persistent” than isolated small populations (Noss et al 1996; Noss 1987; Noss and Harris 1986; Noss 1983). Reducing or minimizing mortality is important for many species, particularly those that are rare, have low fecundity, or exist in small populations. Carnivore populations often fit within these categories.

An important benefit of fencing and wildlife crossings is a reduction in animal-vehicle collisions with large carnivores and other species like elk, deer, and moose. Such mitigation measures are as important to human safety as they are to wildlife conservation. Collisions or near collisions with these large animals are serious highway safety hazards. Human deaths and injuries are common when vehicles collide with large wildlife, or swerve off roadways to avoid collisions. In many rural situations, collisions with large animals, particularly deer, are the most common cause of highway collisions. A recent study by the Western Transportation Institute calculated the average total costs associated with an animal-vehicle collision for three species: $7,890 for deer, $17,100 for elk, and $28,100 for moose (Huijser 2006).

On December 6, 2005 the Southwestern Carnivore Committee held a “Carnivores and Highways” conference to address these issues. Biologists, engineers, and conservationists came together to recommend a suite of best management practices for small, mid-sized, and large carnivores. Those recommendations are the basis for this document.

Safe Passage was written for engineers, biologists, and conservationists in the Western United States and Canada who are working in the field on a day-to-day basis to address the technical aspects of creating the most ecologically effective and economically efficient wildlife crossings structures. In the following pages, you will find practical information on tools for connectivity planning, types of wildlife crossings, and design guidelines for carnivores and other wildlife.