Dimorphisme sexuel et régime alimentaire de l'hermine dans un agrosystème du Québec

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Abstract
Variations in the diet of the ermin (Mustela erminea) were studied from 1978 to 1980 in relation to the relative availability of meadow voles (Microtus pennsylvanicus), the dominant mammal of Southern Quebec agrosystems. The analysis of 328 ermine scat samples showed that the vole does constitute the main prey item, but that the masked shrew (Sorex cinereus), the short-tailed shrew (Blarina brevicauda), and various birds are also important food components. Male ermins have more flexible feeding habits than females, who eat mostly meadow voles whatever their relative abundance. Both males and females fail to make full use of the shrews and avoid prey that weigh more than 50 g. Overlap of their realized alimentary niches is thus considerable except when small mammals are scarce. In that case, males and females use different feeding strategies; however, the hypothesis suggested by J. H. Brown and R. C. Lasiewsky (1972. Ecology, 53: 939–943) does not seem to be confirmed. The evolution of size dimorphism in this small mustelid is discussed; our results confirm the intra-sexual selection hypothesis proposed independantly by S. Erlinge (1979. Oikos, 33: 233–245) and P. J. Moors (1980. Oikos, 34: 147–158).[Journal translation]