Influence of Mississippi alluvial valley rivers on black bear movements and dispersal: implications for Louisiana black bear recovery

American black bear (Ursus americanus) populations were significantly reduced throughout their range, particularly in southeastern North America. Currently, populations in this region are very fragmented, resulting in concern over possible barrier effects of rivers to normal bear movements and dispersal. This is particularly true for Mississippi, where black bear dispersal into the state is critical if populations are to be recovered. Thus, we studied the relative effects of rivercourses on bear movements and dispersal patterns in southeastern Arkansas, 1992-1996. We captured, radiocollared, and uniquely tagged 40 bears and used radiotelemetry to determine their movements. The Mississippi River (width approximate to 1600 m) deflected bear movements, whereas the White River (width approximate to 200 m) was not a barrier to bear movements or dispersal patterns. Frequency of river crossing differed by gender (P = 0.007) and season (P < 0.001). Male bears crossed rivers more frequently than females. Rivers were crossed less from December to March compared to other seasons. Rivers acted as a semipermeable barrier to bear movements and dispersal patterns, which may have major implications for conservation of large mammal metapopulations. Males appear to be influenced less by rivers, so female translocations across rivers may be necessary to recover fragmented bear populations. We provide an example describing direct implications of this study to the recovery of the threatened Louisiana black bear (U. a. luteolus). (C) 2000 Elsevier Science Ltd. All rights reserved.