Is the relationship between predator and prey abundances

Abstract Context. Predator dynamics may be related to prey abundance and influenced by environmental effects, such as climate. Predatorâ¿¿prey interactions may be represented by mechanistic models that comprise a deterministic skeleton with stochastic climatic forcing. Aims. The aim of this study was to evaluate the effects of climate on predatorâ¿¿prey dynamics. The lynx and snowshoe hare predatorâ¿¿prey system in the Kluane region of the Yukon, Canada, is used as a case study. The specific hypothesis is that climate influences the relationship between lynx and hare abundance. Methods.Weevaluate 10 linear relationships between predator and prey abundance and effects of climate.Weuse data on lynx and snowshoe hare abundance over 21 years in the Yukon as the predatorâ¿¿prey system, and three alternative broad-scale climate indices: the winter North Atlantic Oscillation (NAO), the Pacific North American (PNA) index and the North Pacific index (NPI). Key results. There was more support, as assessed by Akaike weights (wi = 0.600), evidence ratio (=4.73) andR2 (=0.77) for a model of predator (lynx) and prior prey (hare) abundance with an effect of prior climate (winter NAO) when combined in a multiplicative, rather than in an additive, manner. The results infer that climate changes the amplitude of the lynx cycle with lower predator (lynx) abundance with positive values of winter NAO for a given hare density. Conclusions. The study provides evidence that predatorâ¿¿prey dynamics are related to climate in an interactive manner. The ecological mechanism for the interactive effect is not clear, and alternative hypotheses are proposed for future evaluation. Implications. The study implies that changes in climate may alter predatorâ¿¿prey relationships.