Global Ecology and Conservation (Sep 2020)
Testing landscape resistance layers and modeling connectivity for wolverines in the western United States
Abstract
In the conterminous United States, wolverines (Gulo gulo) occupy semi-isolated patches of high elevation subalpine habitats at naturally low densities. The long-term success of the wolverine metapopulation requires open space in valley bottoms that link the mountain ranges of the western US to facilitate dispersal. No previous analysis has used empirical data to determine the degree to which dispersing wolverines are sensitive, or not, to differences in habitat quality outside of areas suitable for a home range. This sensitivity is important because it influences conservation actions. Improving wolverine habitat connectivity models among mountain ranges will benefit future wolverine conservation aimed at maintaining gene flow among populations. To determine how to most accurately model wolverine habitat connectivity, we used a resource selection function to model habitat and then generated six circuit theory connectivity maps. Each connectivity map represented a degree of sensitivity to movement within low-quality habitats. We used three validation metrics to compare these different connectivity surfaces and determine which layer best approximated observed wolverine dispersal using relocation data. We found that a strong negative logistic exponential relationship between habitat quality and resistance best described observed wolverine dispersal (c = 8). This suggests that once outside of habitat suitable for a home range, wolverines are only moderately sensitive to changes in habitat quality. However, we found that there is still some lower threshold of dispersal habitat quality for wolverines, as dispersing wolverines follow lower-resistance pathways that connect high-quality habitat and do not move indiscriminately across the landscape. Our results highlight the need to disentangle dispersal data from home range data through validation using dispersal data. Our findings also indicate that the validation of connectivity metrics is an essential component of conservation planning to best support the persistence of species.
