Type of Document Master's Thesis Author Ryan, Christopher W. II Author's Email Address email@example.com URN etd-02698-201736 Title Reproduction, Survival, and Denning Ecology of Black Bears in Southwestern Virginia Degree Master of Science Department Fisheries and Wildlife Advisory Committee
Advisor Name Title Haas, Carola A. Kirkpatrick, Roy L. Vaughan, Michael R. Committee Chair Keywords
- Ursus americanus
- George Washington and Jefferson National Forests
- Exploited population
- Population Dynamics
Date of Defense 1997-12-10 Availability unrestricted AbstractReproduction, Survival, and Denning Ecology of Black Bears in Southwestern Virginia
Christopher W. Ryan
Thirty-four (6 M, 28 F) of 93 black bears (Ursus americanus) captured during summers 1995 and 1996 were equipped with radio-collars. The mean age of male and females captured was 2.5 (n = 63; 2 males not aged) and 4.4 (n = 28) years, respectively. The mean date of females in estrus was 24 July, and we observed one 1.5-year old female in estrus. The average age of primiparity of radio-collared females was 3.0 years; however, we documented fetuses present in a 2-year old noncollared female’s reproductive tract. The average interbirth interval was 1.6 years and 95.4% of females without yearlings produced cubs. The mean litter size was 2.2 and the cub sex ratio was 1.3M:1F.
Hunting, vehicle collisions, poaching, research, and euthanasia accounted for 80.5%, 5.5%, 5.5%, 5.5%, and 2.8%, respectively of the adult and juvenile male mortalities (n = 36). Hunting, vehicle collisions, and research each accounted for 2 of the adult and juvenile female mortalities (n = 6). Annual harvest rates for males in 1995 and 1996 were 36.1% and 45.5%, respectively; corresponding harvest rates for females were 0.0%, and 5.9%. Annual survival rates estimated with Kaplan-Meier for adult females, juvenile females, and cubs were 100.0%, 93.3%, and 70.3%, respectively. Maximum juvenile male survival rates were 52.0% in 1995 and 51.7% in 1996. Maximum adult male survival rates were 50.0% and 80.0% in 1995 and 1996, respectively.
We monitored 31 bears for 39 bear winters with 100% of the known bears denning. Bears denned in trees (41%), rock cavities (32%), excavations (14%), snags (8%), and ground nests (5%). Chestnut oak (Quercus prinus; n = 9), red oak (Q. rubra; n = 8), and tulip-poplar (Liriodendron tulipifera; n = 1) were used as tree dens. Habitat characteristics did not differ between ground dens and tree dens; however, older bears used ground dens more frequently (Z = -2.484, P = 0.013) than tree dens. Fifty-seven percent of bears denned on public land, and we documented one instance of den reuse.
Filename Size Approximate Download Time (Hours:Minutes:Seconds)
28.8 Modem 56K Modem ISDN (64 Kb) ISDN (128 Kb) Higher-speed Access etd.pdf 333.31 Kb 00:01:32 00:00:47 00:00:41 00:00:20 00:00:01
If you have questions or technical problems, please Contact DLA.