Strong Scientific Study Design Creates Solid Results: Colorado’s SH 9 Research Delivered

Strong scientific design of research evaluating transportation-wildlife mitigation can yield definitive results that assist agencies in adaptive management and building future infrastructure. Study results can also help determine if wildlife connectivity goals or performance measures were achieved. This presentation will provide guidance through the example of research on Colorado’s SH 9, on how the science of transportation and linear infrastructure ecology can use standardized methods of placing camera traps and analyzing data to evaluate the efficacy of mitigation to reduce collisions with wildlife and its ability to provide connectivity for multiple species of wild animals. In this study we placed 62 camera traps on multiple sites to evaluate the efficacy of wildlife underpasses, overpasses, 14 escape ramps, and 13 wildlife guards (deterrents). Colleagues collected wildlife-vehicle crash and carcass data. The six year study, while just a small sample of crossing structures, had multiple samples of the same underpass dimensions (n=5) and overpass dimensions (n=2), and other infrastructure. It included a year pre-construction with camera traps at future wildlife crossing sites to determine the species present that would be expected to use the future structures. A camera trap was placed at the wild side of the fence near an entrance of every crossing structure to evaluate what species were nearby but not approaching the structures. While the sample size of infrastructure was small, the repeats of these components allowed for statistical analyses to evaluate several factors important to wildlife use of wildlife crossing structures, escape ramps, and deterrence at wildlife guards. Statistical testing of crash data in the study area and at two controls pre and post construction helped to solidify that crash reductions were almost certainly due to the mitigation. The overall results allowed the researchers to determine:

1. How wildlife that were present at sites pre-construction were either using or avoiding the new structures;
2. The effect of landscape variables on mule deer and other wildlife use of and success rates at the different crossing structures;
3. Teasing out species preferences for structure types versus placement on landscape;
4. The time for acceptance of a structure by elk, and examining preferences;
5. The most effective wildlife guard design;
6. The effective escape ramp designs that intercept wildlife, and that encourage animals to ascend and escape;
7. Through BACI analysis, the reduction in wildlife crashes that could be attributed to the mitigation.

The statistical analyses of various factors were able to show strong results, however, the small sample size ensured all recommendations came with the caveat that this may not be representative of other areas or over time. The goal of this presentation is to encourage others to use similar methods to allow for study comparisons of results.