North American weasels: resource utilization and distribution

Abstract

A livetrapping program, augmented by enclosure experiments, was undertaken to study resource utilization by ermine (Mustela erminea) and long-tailed weasels (M. frenata) in southern Ontario. Data on food habits, habitat preferences, foraging strategies, and competitive interactions were collected. Based on this information, a theory was formulated to explain the distribution or North American weasels. Ermine fed primarily on meadow voles (Microtus pennsylvanicus) and had body diameters closely approximating those of meadow voles, enabling them to readily exploit these items in subnivean and subterranean environments. Long-tailed weasels were larger and their feeding habits were more general. Dietary overlap between the two species in areas of sympatry was 57.5%. Regarding habitat preferences, ermine selected successional communities, whereas long-tailed weasels showed no preferences. Overlap in areas of sympatry was 76.9%.Long-tailed weasels appear to be limited in their northward distribution by snow cover which restricts the size of foraging spaces, thereby conferring an advantage to the smaller weasels. Conversely, the southward distributions of ermine and least weasels (M. nivalis) appear to be limited by interference interactions with long-tailed weasels. Where ermine and least weasels are sympatric, size differences and general distributions suggest that they hunt different prey in different habitats.