Masters Thesis

Evaluating the Effect of Moisture in Wildlife Crossing Tunnels on the Migration of the California Tiger Salamander, Ambystoma californiense

Expanding road networks cut through ecosystems causing habitat fragmentation, genetic isolation, and wildlife mortality. Wildlife crossing structures are often used as a solution to overcome this growing problem, but are frequently installed without further study on the features that can influence their efficacy. We addressed this issue by investigating the effect of moisture levels inside road tunnels on the movement of California tiger salamanders (Ambystoma californiense) during their annual migration. Specifically we studied the effects of moisture on the rate of tunnel completion and the speed at which individuals traversed a tunnel. Sixty-four individuals were used in this study, and 28 completed the tunnels regardless of moisture levels. Our results showed that moisture levels had no effect on the probability of tunnel completion or rejection, but had an effect on the speed of movement, resulting in individuals spending 33% less time traveling through wet tunnels. Stronger precipitation increased the probability of completions and decreased the speed of movement through tunnels. Our findings suggest that internal moisture levels have little effect on the use of road tunnels and the migration of A. californiense. Rather, external precipitation drives tunnel usage and migratory behavior. Nonetheless, our study demonstrated the successful use of wildlife crossing structures in safely facilitating A. californiense under a hazardous roadway.

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