Temporal variation in site fidelity: scale-dependent effects of forage abundance and predation risk in a non-migratory large herbivore
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Large herbivores are typically confronted by considerable spatial and temporal variation in forage abundance and predation risk. Although animals can employ a range of behaviours to balance these limiting factors, scale-dependent movement patterns are expected to be an effective strategy to reduce predation risk and optimise foraging opportunities. We tested this prediction by quantifying site fidelity of global positioning system-collared, non-migratory female elk (Cervus canadensis manitobensis) across multiple nested temporal scales using a long-established elk–wolf (Canis lupus) system in Manitoba, Canada. Using a hierarchical analytical approach, we determined the combined effect of forage abundance and predation risk on variation in site fidelity within four seasons across four nested temporal scales: monthly, biweekly, weekly, daily. Site fidelity of female elk was positively related to forage-rich habitat across all seasons and most temporal scales. At the biweekly, weekly and daily scales, elk became increasingly attached to low forage habitat when risk was high (e.g. when wolves were close or pack sizes were large), which supports the notion that predator-avoidance movements lead to a trade-off between energetic requirements and safety. Unexpectedly, predation risk at the monthly scale increased fidelity, which may indicate that elk use multiple behavioural responses (e.g. movement, vigilance, and aggregation) simultaneously to dilute predation risk, especially at longer temporal scales. Our study clearly shows that forage abundance and predation risk are important scale-dependent determinants of variation in site fidelity of non-migratory female elk and that their combined effect is most apparent at short temporal scales. Insight into the scale-dependent behavioural responses of ungulate populations to limiting factors such as predation risk and forage variability is essential to infer the fitness costs incurred.
KeywordsAntipredator response movement Risk effect Trade-off Ungulates
This project was supported by grants and logistical support from Riding Mountain National Park, Canada and financial support from Manitoba Conservation, University of Saskatchewan, University of Manitoba, and PrioNet Canada. We thank Richard Caners for supplying the forage abundance data and Stephen Webb for helpful discussions on elk movement and predation risk effects. Göran Ericsson, Joris Cromsigt, and one anonymous referee provided many helpful and constructive comments on a previous version of this manuscript. All animals were captured and handled in accordance with the guidelines of the Canadian Council on Animal Care and approved by the ethics committees at the University of Manitoba (protocol number F01-037), the University of Saskatchewan (protocol number 20060067), and in accordance with the Canadian Environmental Assessment Registry (ref. 03-01-473).
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