The Reproductive Biology, Winter Dormancy and Denning Physiology of Black Bears in Great Smoky Mountains National Park

Black bear reproduction, winter dormancy and denning physiology were studied during June 1984 to May 1986 in the northwest quadrant of Great Smoky Mountains National Park, Tennessee. Information was obtained from 30 individual females captured 35 times. Additional information on mast indices, lactation and den utilization were summarized from within the study area for the period from 1978-1988. Breakaway collar retention varied significantly between years (1984, N=10, X=394 days vs. 1985, N=5, X=196 days, P\u3c0.05). Maximum production potential indices calculated for white, red and all oaks for 1984 and 1985 were 8.74, 19.99, 15.52%, and 35.06, 37.73, 36.45%, respectively. Regression analysis showed a significant relationship between white oak mast maximum production potential indices and the number of lactating females observed seasonally between 1979-1988 (winter: R2=0.69, P\u3c0.003, summer: R2=0.45, P\u3c0.03, annually: R2=0.62, P\u3c0.007). Using vulval examination, 12 females captured in 1984-1985 were determined to be in estrus. Most observations of estrus occurred between 20 June and 12 August. Females subjectively determined to be in estrus had significantly lower levels of estradiol (X=11.06 pg/ml, P\u3c0.005) than females showing no signs of estrus (X=25.44 pg/ml). Salivary estradiols from females observed in estrus were also lower than those from anestrus females; though not significantly (X=10.12 pg/ml vs. X=13.89 pg/ml, P\u3e0.2). The minimum reproductive age for female black bears was 5.2 years with an average of 2.2 cubs/litter. Mean age at first litter was affected largely by nutrition. Four reproductive skips were observed in first litter females following the mast failure of 1984. Females entered dens from 5 to 15 December during 1984 and from 27 November to 30 December during 1985. Females delayed den entry during years of abundant mast. Den utilization data were compiled from 1978 to 1986. Seventy-two den sites for 27 adult females were categorized. Tree dens were used more frequently than ground dens (58.3%, N=42 vs. 41.7%, N=30, respectively). However, a majority of litters (16/29, 55.1%) were produced by females denning on the ground. Ratios of serum urea to creatinine showed slight seasonal decreases (not significant) in 3 of 4 years examined. Urea to creatinine ratios obtained from 5 denned females were not indicative of bears in a physiological state of dormancy (X=30.96 pg/ml). This finding coupled with observations on winter lethargy at den sites, suggests that the degree of dormancy attained by black bears may differ both within and between geographic regions