Potential Spatial Barriers to Black Bear Dispersal and Population Connectivity in Alabama

Corridors are important for many species, especially black bears (Ursus americanus), which use corridors for juvenile dispersal and connectivity among local and regional populations. Black bears are native throughout Alabama; however, historic populations have diminished, in part from habitat degradation and decreased connectivity. At present, only two small populations of black bears occur in Alabama. One is a newly recolonized population in northern Alabama, whose numbers are growing quickly. The other is a remnant population in the Mobile River Basin that is genetically isolated from other black bear populations in the southeastern U.S. Neither population exhibits the spatial growth patterns characteristic of what small populations could achieve. One proposed explanation for the observed limited spatial growth and genetic isolation is a lack of corridors, resulting in decreased connectivity. In this study, we created Geographic Information System (GIS) models of corridor suitability for black bears in Alabama. We used reports and sightings of bears from 1911 to 2020 to parameterize and test the model. ROC curves confirmed that the GIS models were good predictors of proportional probability of use of a location by black bears. Models indicated that a lack of available corridors in south Alabama may be limiting gene flow with black bear populations in Florida. Conversely, potential corridors in north Alabama may be facilitating population connectivity and expansion.

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