Population Ecology of Black Bears in the Alleghany Mountains of Virginia

The Cooperative Alleghany Bear Study (CABS) was a 10-year study conducted on 2 areas and designed to investigate the ecology of a hunted population of American black bears (Ursus americanus) in the Alleghany Mountains of western Virginia. Over the course of our research, we handled 1,041 individual bears >18 months old and gathered reproductive data from females during 424 bear-winters. My analyses of 183 litters indicate that reproductive rates were high with relatively large litters (mean = 2.49 cubs / litter) and younger (3–4-year-old) females having smaller litters than older (> 5 years old) females. Overall cub sex ratios did not differ from 1M:1F; however, female cubs were over-represented in 4-cub litters. Most cubs were born in January (mean = January 17) and younger females had later parturition dates than older females. Bears on our study areas had relatively early ages at primiparity (mean = 3.8 years old) and few missed reproductive opportunities. Hard mast failure apparently resulted in periodic reproductive failures and subsequent reproductive synchrony, which I tracked using 5 indices. The amplitude of oscillations in reproductive synchrony dampened through time after each synchronizing event. The population contained substantially more females than males; however, males were more vulnerable to trapping than were females. Population size was determined using genetic and photographic capture-recapture estimators. Density estimates were relatively high and approached 1 bear / km2. Annual survival rates were high for cubs (0.87) and females (0.91). For males, annual survival rates were lower, particularly for 1–3-year-olds (0.57). Excluding hunting mortality, natural survival rates were high (0.98) for all >1-year-old bears on our study areas. The results of Leslie Matrix and Program RISKMAN models indicated a growing population. A Leslie Matrix model incorporating the effects of a 5-year-cyle of mast-failure-induced reproductive failure yielded a lambda = 1.13. To reach the objective of 0 population growth prescribed for some areas of Virginia, increased levels of hunting mortality on adult (>3-year-old) females would likely be necessary.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Fisheries and Wildlife Sciences

Department dc:contributor.department

Fisheries and Wildlife Sciences

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2005

Author dc:creator

• Bridges, Andrew Scott

Chair dc:contributor.committeechair

• Vaughan, Michael R.

Committee members dc:contributor.committeemember

• Steffen, David E.
• Walters, Jeffrey R.
• Stauffer, Dean F.

• survival
• American black bear
• demographics
• population dynamics
• Reproduction
• Ursus americanus

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

etd-05172005-181300

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/27754