Spatiotemporal Patterns of Macrohabitat Use by Female Black Bears during Fall

Abstract

We compared habitat use and movements of 82 radio-collared female black bears (Ursus americanus) at 3 dissimilar study areas in Maine during fall from 1986 to 1988. We focused on the use of northern hardwood forests containing American beech (Fagus grandifolia). Many beech forests in the northeastern United States have been infected with beech bark disease, which may limit beechnut availability. At the Spectacle Pond and Stacyville study areas, annual variation in habitat use was pronounced and was related to abundance of beechnuts. Bears used hardwood forests more when beechnuts were abundant (1986 and 1988) than when beechnuts were scarce (1987). At the Bradford study area, where habitat was more diverse and beech trees were less common, habitat use did not vary annually, and use of hardwoods and softwoods was proportional to availability. Maximum fall movements by bears, away from summer ranges, did not vary annually within areas. Fall movements were greater for bears at Stacyville (median = 7.3 km, n = 19 bear-years) than at Spectacle Pond (median = 1.3 km, n = 52) or at Bradford (median = 0.9 km, n = 28) and reflected distribution of food resources on a landscape scale. In all areas, most long movements (7.7-78.6 km) during fall were to hardwood forests when beechnuts were abundant. Bears usually denned within or near (<1.0 km) their summer ranges despite long fall movements. We provide recommendations for managing northern hardwoods to maintain beechnut production. Int. Conf. Bear Res. and Manage. 9(l):339-348 Reproduction and recruitment of black bears have been correlated with availability of mast (Rogers 1987, Eiler et al. 1989, Elowe and Dodge 1989). American beech is a component of the northern hardwoods forest type, and beech mast is eaten by black bears during fall (Hugie 1982, Elowe and Dodge 1989). Beech bark disease has caused extensive mortality of beech trees throughout northeastern United States (Houston 1975, Miller-Weeks 1983), with mortality exceeding 50% in some forests in Maine (Miller-Weeks 1983). In North America, beech bark disease is caused by a fungus (especially Nectria coccinea var. faginata) that infects the feeding wounds in the bark made by the beech scale (Cryptococcus fagi) (Houston 1975). This disease was first reported at Maine in the 1930s (Houston 1975), but another disease outbreak may be occurring now because of the age and size structures of recovering beech forests (Houston 1975, Houston and Valentine 1988). Beech bark disease can reduce beechnut production in infected forests (CM. Costello, Adirondack Ecol. Cent., pers. commun.). Habitat use by black bears has been examined in the Northeast (Hugie 1982, Lamb 1983, Elowe 1984, Meddleton 1989), but these studies did not test relationships between availability of mast and habitat use by bears during fall. Previous studies focused on spring and summer (Meddleton 1989), combined data for all seasons (Hugie 1982, Lamb 1983), or combined data from several years in which abundance of mast differed (Hugie 1982, Elowe 1984). Seasonal movements by black bears are mainly governed by distribution, phenology, and abundance of preferred foods (Garshelis and Pelton 1981, Pelchat and Ruff 1986, Rogers 1987). Comparing fall movements of bears from different environments should provide insight into foraging behavior and importance of forest ypes. Except for Hugie (1982), previous studies in northeastern United States were conducted at only 1