A sampling of wildlife use in relation to structure variables for bridges and culverts under I-90 between Alberton and St. Regis, Montana
Habitat fragmentation, habitat loss, and human caused mortality are the major factors contributing to wildlife decline throughout the world. High-speed, heavily-used highways can divide formerly contiguous blocks of habitat and isolate wildlife populations. Underpasses and culverts have the potential to mitigate the negative impacts of roads on wildlife populations by maintaining connectivity between wildlife populations and decreasing wildlife collisions with vehicles. Using heat and motion sensitive cameras, we monitored seven underpasses and three culverts for ten months along Interstate 90 in western Montana. We documented the type and frequency of wildlife use and compared the level of use to variables associated with the structures. Wildlife use was most frequent at underpasses and limited in culverts. Ungulates were the primary users of underpasses with limited use by medium and large carnivores. We found no significant relationships between wildlife use and structural variables. This is partly due to a small sample size but could be the result of animals using structures opportunistically.