Compensatory behavior of Ensatina eschscholtzii in biological corridors: a field experiment

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Abstract
Despite the general lack of theoretical or empirical support, biological corridors are assumed to mitigate the detrimental effects of habitat fragmentation by increasing landscape connectivity. To test the hypothesis that mechanisms which affect immigration rates from a source to a target patch are affected by the presence of a corridor in an otherwise unsuitable matrix, we created two strongly contrasting pathways in replicated field experiments. One pathway type included only bare mineral soil, the other included a potential corridor. We conducted these experiments with Ensatina eschscholtzii, a salamander in the family Plethodontidae. Pathways with surface organic material removed provided a harsh environment for E. eschscholtzii, which was reflected by lower selection, shorter residency time, and higher movement rates than on pathways that contained vegetation (corridor pathways). However, the numbers of E. eschscholtzii reaching target patches connected by corridor pathways were greater than those reaching target patches connected by bare pathways only in plots in which the matrix environment seemed most severe. Our results suggest that identifying candidate corridor areas on conservation maps might be difficult because animals may show compensatory behavioral responses to different types of habitat separating source and target patches. We argue that knowledge of a species' habitat-specific dispersal behaviors is critical to reliably designating corridors as functional components of reserve design.