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 obtained 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 interactions between mink and muskrat. Model selection results did not differ among ecozones, and indicated that a predator-prey autoregressive model incorporating a delayed density-dependent term best described both the mink and muskrat harvest time series. Subsequent analysis of autoregressive coefficients and estimated lags indicated that mink and muskrat interactions vary throughout Canada. In western Canada, the trophic interactions appear to be strong, and mink population cycles lag behind muskrats 2-3 years. In central Canada, mink harvests lagged behind muskrats 1 year, and mink and muskrat interactions in central Canada, with the exception of the Hudson Plains ecozone, were intermediate. In eastern Canada, the trophic interactions appeared weakest, and there were no distinct time lags between mink and muskrat. Stronger interactions in western Canada may be a result of decreased prey diversity, forcing mink to specialize more on muskrats, whereas comparatively stronger perturbations stemming From other trophic interactions may alter the estimated interaction between mink and muskrat in eastern Canada.