Date of Award
Master of Science
Wildlife and Fisheries Science
Michael R. Pelton
Gary F. McCracken, Ralph W. Dimmick, Joseph C. Daniel Jr.
The reproductive biology and denning ecology of black bears were studied in the Great Smoky Mountains National Park and Cherokee National Forest. The majority of information was collected from 36 radio-instrumented females monitored from June 1980 to May 1982.
Females entered dens from 21 November to 16 January (x=20 December, n=38), and emerged from 18 March to 4 May (x=10 April, n=41), for an average denning period of 113 days. Females with newborn cubs denned significantly longer (P< 0.001) than other females. Tree denning females emerged later and remained in dens longer than others.
Twenty-five ground dens and 33 tree dens were examined. Significant differences (P< 0.005) in den utilization were observed between winters, with more tree dens being utilized during the winter of 1980-81 (79.3%) than in the winter of 1981-82 (34.5%).
Females in estrus were captured from 22 June to 12 July (n=5) and 5 August to 18 August (n=3). Serum estradiol-17B concentrations in females displaying prominent signs of estrus (x=92.3 pg/ml) were significantly higher (P< 0.001) than in females showing no signs of estrus (x=51.31). Serum estradiol concentrations appeared to be a more reliable indicator of estrus than vaginal smears.
The average age at first litter was 5.2 years, and the average interval between successful litters was 2.15 years, with the majority (11 of 13) of females reproducing in alternate years. Food availability, particularly that of hard mast in the fall, influenced many reproductive parameters, including minimum reproductive age, productivity, and cub survival. White oak mast availability demonstrated the best linear relationship (R2=0.86, P<0.0722) to the percentage of females with newborn cubs in winter dens.
Litter sizes of newborn cubs ranged from 1 to 4 (x=2.58, n=19); a majority of litters (n=16) contained 2 or 3 cubs. The average weight of 35 newborn cubs examined from 28 February to 19 March 1982 was 1.82 kg. Cubs of larger litters weighed significantly less (P<0.0001) than cubs of smaller litters. The sex ratio of litters of newborn cubs and yearlings was 45:55 (18 males, 22 females) and 50:50 (6 males, 6 females), respectively.
Weights of adult females varied by season and by reproductive status. Lactating females dropped from an average weight of 77.4 kg in winter dens to 49.1 kg in June. Also, females with newborn cubs in winter dens weighed an average of 31.0 kg heavier than they did as females with yearlings in winter dens.
Wathen, William Gregory, "Reproduction and Denning of Black Bears in the Great Smoky Mountains. " Master's Thesis, University of Tennessee, 1983.