Regional connectivity for recolonizing American black bears (Ursus americanus) in southcentral USA

Abstract

Landscape connectivity is vital for species conservation in human-modified landscapes, lessening population declines and genetic depression caused by habitat loss and fragmentation. We used concepts from electronic circuit theory to identify potential areas for American black bears (Ursus americanus) that facilitate connectivity between key federally protected areas, determined if black bears used higher quality habitat than available, and examined their distribution relative to human disturbance. We developed a regional (Mississippi, Louisiana, eastern Texas, Arkansas, and Missouri, USA) model estimating landscape resistance to movement using GIS-based features considered to affect black bear space use: land cover type, distance to major rivers, road density, and highway presence. We selected national forests and national wildlife refuges as patches among which to model potential movement. Using citizen-reported black bear sightings from Mississippi and Missouri, we evaluated land cover selection at fine and coarse scales, and validated our model comparing current density between bear sightings and random locations. Black bear sightings occurred in areas of higher current density compared to random locations (p<0.001), suggesting our connectivity model had good performance for characterizing areas bears will use at a coarse scale. However, black bears did not always choose high quality habitat for movement at a coarse scale, and avoided areas of human disturbance at a finer spatial scale. Contiguous forested areas outside protected areas and riparian corridors along major rivers were identified as most likely to facilitate connectivity. The relative importance of protected areas in maintaining regional connectivity was influenced by size, location, and amount of forest cover. Highways appeared as semi-permeable barriers to movement that intersected several connectivity pinch points. Management to maintain or improve connectivity in identified high connectivity areas, including forest retention, preservation of riparian buffers, and highway mitigation techniques at pinch points, may facilitate black bear recolonization and aid broader conservation objectives.