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Published on: August 8, 2017
Predator-driven component Allee effects in a wild ungulate.
Aurélie Bourbeau-Lemieux1, Marco Festa-Bianchet, Jean-Michel Gaillard
1Département de Biologie, Université de Sherbrooke, 2500 Boulevard de l'Université, Sherbrooke, QC J1K2R1, Canada.
Ecology Letters
|February 16, 2011
Summary
Predation by cougars created Allee effects in bighorn sheep, where survival increased with population size. This predator-driven effect worsened population declines and extinction risk.
Area of Science:
- Ecology
- Population Dynamics
- Wildlife Biology
Background:
- Negative density dependence influences large vertebrate populations.
- Allee effects, or positive density dependence, impact small populations.
- Predation can generate Allee effects, with indirect effects on population dynamics.
Purpose of the Study:
- Quantify Allee effects and indirect predation effects in wild populations.
- Investigate the long-term impact of cougar predation on bighorn sheep population dynamics.
Main Methods:
- Long-term monitoring (27 years) of a bighorn sheep population (Ovis canadensis).
- Analysis of survival rates in relation to population size and predation events.
- Assessment of cougar (Puma concolor) predation impacts on lamb and ewe survival and growth.
Main Results:
- Cougar predation episodes significantly depressed bighorn sheep survival.
- Positive relationships observed between lamb survival and population size below a threshold.
- Predation also reduced lamb growth, contributing to mortality and exacerbating population declines.
Conclusions:
- Predator-driven Allee effects can amplify other environmental stressors.
- These effects increase the extinction risk for small, vulnerable populations.
- Understanding these dynamics is crucial for effective wildlife conservation and management.
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