In the early 1970s, Erlinge (1974) began research on common weasels in a mixed-age conifer-deciduous alder/oak woodland in southern Sweden. The study area was covered with a rich field layer of grass in all but the oldest spruce woodland, where the trees had grown thick enough to shade out the grass, and had stone walls to provide the weasel's favorite refuges. Field voles were common in the grass among young spruce trees, and so were wood mice and bank voles in the alder/ oak woodland, but few small rodents, if any, lived in the oldest plantation.
As expected, the resident common weasels lived where most small mammals lived. When the study began, in winter, three males and two females resided in the grassiest areas. Nonresidents visited the alder woods occasionally, but no weasel was ever caught among the oldest spruces. The residents seemed content to remain on their chosen home ranges, although there were large areas of similar habitat around each. Four young and three adult males visited but did not settle.
In spring, the resident males began to range farther, covering larger areas and seldom staying in one place for long. By the following autumn, a stable new system was reestablished, including five resident males, of which only one had been present when the study began. As before, the residents settled in the grassy areas and ignored the closed-canopy spruce woodland. No breeding females, and few nonresident males, were caught in the second autumn. Erlinge did not report the sizes of the males' ranges, but mentioned that the females' movements, even in spring, were "less extensive ... one female was trapped 29 times in March and April over an area of about 1.5 ha."
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