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Rights Statements InC/1.0 , Open Access
Journal article
Factors limiting a bighorn sheep population in Montana following a dieoff
Northwest science., Vol.75(3), pp.280-291
2001
Handle:
https://hdl.handle.net/2376/945
Abstract
Conservation and management of bighorn sheep populations is complicated by the species' susceptibility to a multitude of pathogens and the long-term influence of disease upon population dynamics. Small post-dieoff sheep herds are often unable to fully recover to pre-dieoff densities, and researchers have identified several factors limiting such populations including disease, predation, competition, climate, nutritional deficiencies and loss of genetic variability. We studied a small bighorn sheep herd in west central Montana from 1995 to 1997 to identify the mechanisms responsible for poor population performance subsequent to a dieoff in 1984. In contrast to the migratory pre-dieoff population, the current sedentary population was restricted to a small area of low elevation range throughout the year. Whereas we observed limited annual adult mortality due to disease and predation, ewe productivity and lamb recruitment rates were low in all years. Lamb production and survival were highly correlated with summer climatic conditions, with the highest rate of disease-mediated lamb mortality occurring during a summer drought and the lowest rate of ewe productivity occurring subsequent to this drought. Our data suggest that disease continues to play a significant role in this bighorn sheep population, and nutritional quality of summer forage influenced not only sheep immunocompetence and susceptibility to disease but also herd productivity. Winter is generally considered the critical season for ungulate populations in the northern Rocky Mountains, yet summer climatic conditions can have important implications for performance of sedentary, low elevation sheep populations. We suggest that an understanding of population-specific limiting factors is essential to successful management of post-dieoff bighorn sheep herds. Data obtained through rigorous field studies facilitate the development and implementation of efficient, biologically sound strategies to improve performance of these populations.
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Details
- Title
- Factors limiting a bighorn sheep population in Montana following a dieoff
- Creators
- Terrence A. Enk (Author)Harold D. Picton (Author)James S. Williams (Author)
- Publication Details
- Northwest science., Vol.75(3), pp.280-291
- Academic Unit
- Northwest Science
- Publisher
- WSU Press
- Identifiers
- 99900501560601842
- Copyright
- In copyright ; openAccess ; http://rightsstatements.org/vocab/InC/1.0/ ; http://purl.org/eprint/accessRights/OpenAccess
- Language
- English
- Resource Type
- Journal article