Spatial variation in mink and muskrat interactions in Canada

We investigated the spatial attributes of mink (Mustela vison) and muskrat (Ondatra zibethicus) interactions in Canada using 160 geographically paired historic time series of mink (n = 80) and muskrat (n = 80) harvest data ob tained from Hudson's Bay Co. Archives. All series were 25 years in length ( 1925-1949) and were distributed primarily throughout five ecozones. We used autoregressive models and cross-correlation analysis to characterize the i nteractions between mink and muskrat. Model selection results did not diffe r among ecozones, and indicated that a predator-prey autoregressive model i ncorporating a delayed density-dependent term best described both the mink and muskrat harvest time series. Subsequent analysis of autoregressive coef ficients and estimated lags indicated that mink and muskrat interactions va ry throughout Canada. In western Canada, the trophic interactions appear to be strong, and mink population cycles lag behind muskrats 2-3 years. In ce ntral Canada, mink harvests lagged behind muskrats 1 year, and mink and mus krat interactions in central Canada, with the exception of the Hudson Plain s ecozone, were intermediate. In eastern Canada, the trophic interactions a ppeared weakest, and there were no distinct time lags between mink and musk rat. Stronger interactions in western Canada may be a result of decreased p rey diversity, forcing mink to specialize more on muskrats, whereas compara tively stronger perturbations stemming From other trophic interactions may alter the estimated interaction between mink and muskrat in eastern Canada.