Demographic Analysis of a Black Bear Population in the Great Dismal Swamp

Abstract

During April 1984-August 1986, 101 black bears (Ursus americanus) (71 M, 30 F) were captured 120 times in the Great Dismal Swamp (GDS) National Wildlife Refuge (NWR) and surrounding area, a forested wetland in eastern Virginia and northeastern North Carolina. Males dominated the capture sample (P 9 years old were male (n = 5). Litter size (n = 12, : = 2.1), suspected modal age at primiparity (4 yr), and interbirth interval (approx 2 yr) were indicative of good-quality habitat. Estimated annual survival rates were 0.87 for females (-1.5 yr) and 0.59 for males (?2.5 yr). Causes of mortality included legal and illegal harvest, vehicle collisions, depredation permit kills, research, and intraspecific predation. Estimated bear density was 0.52-0.66 bears/km2, corresponding to 286-368 bears for the 555-km2 study area. Present population management (protection from hunting and no public vehicular access) should be continued in the GDSNWR. The small effective population size (N, = 56) in the GDS indicated the need for study of dispersal and genetics in the GDS and other southeastern wetland populations to determine the degree of isolation and extent of genetic variability. Black bear conservation strategies in the southeast are critical due to increasing habitat fragmentation. J. WILDL. MANAGE. 53(4):969-977 The ecology of black bears in southeastern wetlands has been the subject of limited study (Hamilton 1978, Smith 1985). Islands of wetland habitats, primarily swamps and pocosins (Sharitz and Gibbons 1982), provide the last remaining refuges for black bear on the Atlantic Coastal Plain (Monschein 1981, Zeveloff 1983). Large hardwood swamps and pocosins provide excellent denning habitat (Hamilton and Marchinton 1980, Hellgren and Vaughan 1989), diverse food supplies, and protection from disturbance (Hamilton 1978, Monschein 1981). However, dynamics of wetland populations remain poorly understood. The GDS, an 850-km2 forested wetland on the Virginia and North Carolina border, supports the last breeding population of black bears in eastern Virginia and extreme northeastern North Carolina. The 1973 establishment of GDSNWR, which occupies the core of the swamp, placed management responsibility for the bear population on the U.S. Fish and Wildlife Service (USFWS). The need for population estimates and evaluation of habitat suitability for proper bear management in GDSNWR was ide tified (Bur. Sport Fish. and Wildl. 1974), yet bear-related research has not met this need. Management for bears in the GDSNWR is limited to protection from hunting. The GDS population, although afforded sanctuary in the refuge and unhunted in North Carolina since the early 1970's, is exploited on private swamp land in Virginia at a rate of 9.4 bears/year since refuge establishment (Anonymous 1984). The potential of the unhunted population in GDSNWR to act as a reservoir for black bear reproduction and dispersal in the Atlantic Coastal Plain is unknown. In recent years, clearing of privately-owned GDS land for agricultural or residential development has accelerated, making GDSNWR vital as a sanctuary for the bear population. Information such as sex and age distribution, age at primiparity, birth rate, survival, and density of the bear population in the GDS is necessary to predict results of bearrelated management actions. Our objective was to characterize dynamics of the black bear population in the GDS. We acknowledge the cooperation of the USFWS, Virginia Department of Game and Inland Fisheries, North Carolina Wildlife Resources Commission, and the Department of Fisheries and Wildlife Sciences, Virginia Polytechnic Institute and State University. Particularly helpful were D. J. Schwab, R. D. Mc1 Present address: Campus Box 218, Caesar Kleberg Wildlife Research Institute, Texas A&I University, Kingsville, TX 78363.