IUCN / SSC Cat Specialist Group - Digital Cat Library |
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| Villepique, J.T.; Pierce, B.M.; Bleich, V.C.; Andic, A.; Bowyer, R.T. | |
| Range abandonment by ungulates: Predator avoidance or response to habitat changes induced by drought? | |
| 2014 Conference Proceeding | |
We investigated influences of risk of predation by mountain lions (_Puma concolor_ ), measures of topographic ruggedness at multiple scales, and vegetation, land, and snow cover, on resource selection in winter by Sierra Nevada bighorn sheep (_Ovis canadensis sierrae_), an endangered taxon. We hypothesized that those mountain ungulates would trade off rewards accrued from use of critical low-elevation habitat in winter for the safety of areas with reduced risk of predation. We also investigated the tradeoff between forage and risk of predation by testing the hypothesis that differences in quality of forage at low-elevations versus high-elevation were reduced in years of below-average precipitation than in wet years, yielding a reduced benefit of migration to low-elevations during drought years. Sierra Nevada bighorn sheep did not trade off benefits of forage for reduced risk of predation, but selected areas of high solar radiation, where risk of predation by mountain lions was greatest, while mitigating indirect risk of predation by selecting for steep, rugged terrain. Bighorn sheep selected more strongly for areas where mountain lions were active and killed bighorn sheep, than for low elevation habitat in winter, likely because mountain lions were most active in those areas of bighorn winter ranges overlapping ranges of mule deer (_Odocoileus hemionus_), where both ungulates accrued forage benefits. We demonstrated reduced benefit of migration to low elevation during drought years, when the difference in quality of forage was significantly lower than in years of above-average precipitation, providing an alternative explanation to the predator-induced abandonment hypothesis for the disuse of low-elevation winter range observed during drought years. |
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