Assessing American black bear habitat in the Mobile–Tensaw Delta of southwestern Alabama

Abstract

American black bears (Ursus americanus) have been extirpated from all but a few areas in southwestern Alabama, and the remaining habitat is being rapidly lost to development. Remnant bear populations exist near extensive (>125,000 ha) bottomland hardwood forests in the Mobile–Tensaw Delta (MTD), but those bottomland areas are rarely used by bears. Reintroduction of black bears to the MTD may improve viability of the remaining bear populations in southwestern Alabama. To evaluate the suitability of this area for bears, we compared habitat conditions at the MTD with similar alluvial habitats at White River National Wildlife Refuge (White River NWR), where bears are numerous. We measured overstory, midstory, and understory vegetation in the MTD and on the North and South management units at White River NWR. We used principal components analysis and principal variable selection to identify 9 variables associated with 5 principal components (hard mast, soft mast, cavity tree availability, large tree availability, and total basal area) that best explained variation among study areas. Differences among the study areas were associated with hard mast, soft mast, and cavity tree availability (P ≤ 0.001). Hard and soft mast production in the MTD was lower than at White River NWR, but we believe it was adequate. However, suitable den trees, which may be a critical habitat component given the duration and severity of winter flooding, appeared to be lacking in the MTD.