| Type of Document |
Dissertation |
| Author |
Bridges, Andrew Scott
|
| Author's Email Address |
abridges@vt.edu |
| URN |
etd-05172005-181300 |
| Title |
Population Ecology of Black Bears in the Alleghany Mountains of Virginia |
| Degree |
PhD |
| Department |
Fisheries and Wildlife Sciences |
| Advisory Committee |
| Advisor Name |
Title |
| Vaughan, Michael R. |
Committee Chair |
| Stauffer, Dean F. |
Committee Member |
| Steffen, David E. |
Committee Member |
| Walters, Jeffrey R. |
Committee Member |
|
| Keywords |
- survival
- American black bear
- demographics
- population dynamics
- reproduction
- Ursus americanus
|
| Date of Defense |
2005-04-29 |
| Availability |
unrestricted |
Abstract
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.
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