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Denning Characteristics of Black Bears in the San Gabriel Mountains of Southern California





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Denning habits of San Gabriel Mountain black bears were studied during the winters of 1987 through 1990. Mean denning period of five male bears was mid-November to mid-March. Denning periods for all bears ranged from late October to late March. Bears entered dens significantly later in 1988 than in 1987, 1989, and 1990 (P < .05). We speculate that fluctuations in food item availability might have affected the onset of denning. Exit dates (x 2 = 1.2, P = 0.758) and denning duration (x 2 = 4.79, P — 0.1 87) were not significantly different between years. Dens were located primarily in tree cavities {Pseudotsuga macro- carpa and Quercus chrysolepis) or under large boulders. All bears with more than one known den site reused a previous den. No incidents of winter activity were observed.