Habitat selection of coexisting competitors: a study of small mustelids in northern Norway

The coexistence of two very similar species, stoat and least weasel, has puzzled many researchers. From their ecology it is expected that they do not coexist, not locally at least, and still they seem to do. We reviewed the specific hypotheses proposed to explain their coexistence and related these to general theories of competitive coexistence. To test these conjectures, we studied the habitat selection of least weasels and stoats on landscape and on local scale. The study was performed during the winters, the most critical season, in years 1986-2001 in northern Norway. Stoats were usually more numerous than least weasels. Stoats showed preference for productive areas both at the landscape and at the habitat scale and appeared stereotypic in their habitat selection. Least weasels were more generalized and flexible in their habitat selection. Contrary to results reported in many studies, least weasel did not react to the presence of stoats and were not excluded from the areas with stoats. We suggest that in the conditions of northernmost Fennoscandia, the two species exhibit a variant of classical competitive coexistence. Both species have a shared preference for rodents, but the access to exclusive alternative prey in stoats allows their coexistence with least weasels, which are more efficient predators on rodents. We suggest that more attention should be paid on survival resources, exploited during times of low resource density, when studying the coexistence between close competitors.