Evaluation of Wildlife Crossing Structures and Fencing on US Highway 93 Evaro to Polson Phase I: Preconstruction Data Collection and Finalization of Evaluation Plan

Abstract

The US 93 reconstruction project on the Flathead Indian Reservation in northwest Montana represents one of the most extensive wildlife-sensitive highway design efforts to occur in the continental United States. The reconstruction will include installations of 42 fish and wildlife crossing structures and approximately 15 mi (24 km) of wildlife exclusion fencing for a total investment of over $9 million. This report documents the success of using a context-sensitive approach to collaboratively redesign a rural highway within a multiple use landscape that accommodates the needs and concerns of different institutions, cultures and priorities. Further, this report introduces baseline field data collection methods and results that are being used to evaluate how the wildlife crossing structures and wildlife fencing affect deer- and bear-vehicle collisions and movements in a multiple-use rural landscape. The preconstruction data summarized here, and in combination with complementary post-construction data, will address the following goals of the evaluation study: (1) determine what effect US 93 wildlife crossing structures and fencing have on the frequency of animal-vehicle collisions and successful animal highway crossings; (2) document the design decision-making processes and lessons learned as a “case study”; and (3) identify best management practices and further research. These issues are addressed via a literature review of important considerations related to locating, designing, and evaluating the effectiveness of wildlife crossings and exclusion fencing; a case study and project history; summary and synthesis of field data collection efforts; overview of other relevant and repeatable field studies; and a discussion about the measures of effectiveness and post-construction data collection recommendations. The ultimate value of the information in this report will be realized when the reconstruction is complete and post-construction field data is collected to comparatively assess the effect of the wildlife mitigation on the parameters of interest identified in the goals. Perhaps one of the most important insights gained from the preconstruction research is that, due to the myriad sources of unquantifiable variation in the environment, many years of monitoring are necessary to make valid inferences. Given the paucity of long-term, before-after field studies assessing the effects of wildlife exclusion fencing and crossing structures on wildlife and driver safety, the US 93 wildlife mitigation evaluation, when completed, will provide useful results, lessons learned, and best management practices to guide other wildlife mitigation efforts in the future.