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Reproduction, Survival, and Denning Ecology of Black Bears in Southwestern Virginia

by Ryan, Christopher W.

Abstract (Summary)
Reproduction, Survival, and Denning Ecology of Black Bears in Southwestern Virginia

Christopher W. Ryan

Abstract

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√Ęs 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.

Bibliographical Information:

Advisor:Dr. Michael R. Vaughan; Dr. Carola A. Haas; Dr. Roy L. Kirkpatrick

School:Virginia Polytechnic Institute and State University

School Location:USA - Virginia

Source Type:Master's Thesis

Keywords:fisheries and wildlife

ISBN:

Date of Publication:01/29/1998

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