Den sites may include holes up the trunks and in roots of trees through forest habitat (Murphy & Dowding 1994) or in piles of logs, ditches, and isolated patches of scrub in open habitat. In Ireland, of 19 dens belonging to three radio-tracked individuals, 15 were in underground burrows (nine made by rats, four by rabbits, one by a mouse, and one unknown), three in piles of sticks or stones, and one up a tree (Sleeman 1990). One stoat den found in northwest Greenland by Sittler (1995) had been built in the wool of a muskox carcass.

Lisgo (1999) classified seven different types of rest sites or dens used by her stoats, all underground. The dens were in squirrel middens, in tunnels through moss or root systems used by snowshoe hares or chipmunks, under logging slash, under branches or trunks of natural deadfalls, in holes at the bases of trees or snags, in moss hummocks, or in the upturned roots of trees. All stoats used more than one den. Of 42 dens used by male stoats, the order of preference was squirrel middens (55%), holes in trees or snags (24%) and all the rest (<7% each). Of 37 sites used by females, the preferred sites were under logging slash (41%), in holes in trees or snags (30%), in natural deadfalls (16%), and all the rest (<5% each). This difference in rest sites used by the two sexes is just as one would expect from the difference in their preferred hunting areas.

The safest dens are those with the smallest entrances, which keep out unwelcome visitors, including other weasels. Two of the female stoats with young observed by Erlinge (1979a) had chosen dens with access holes too tight to admit a male, and likewise, the entrances to dens of longtails measured by Gehring and Swihart (2000) averaged 30 mm for females and 40 mm for males . Female stoats move about less during the breeding season (Robitaille & Raymond 1995), and females with small young are likely to stay close to their dens except when it is necessary to shift their young between den sites. In New Zealand, Murphy and Dowding (1995) observed an adult female moving her young 500 m to a new den; Dowding and Elliott (2003) identified 14 dens that were used sequentially by more than one collared stoat within 3 months, plus nine dens that were used by both stoats and feral ferrets.

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