Advances in New Zealand mammalogy 1990–2000: Stoat and weasel

After combining several phylogenetic analyses, Bininda-Edmonds (1999) reached the conclusion that the stoat is most closely related to the mountain weasel M. altaica, but is also very close to the common weasel (M.nivalis) and the long-tailed weasel (M.frenata).The next closest relatives are New World species, the Colombian weasel M. felipei and the tropical weasel M. africana, both previously considered to be part of the sub-genus Grammogale.The change to a white winter coat, typical of stoats living where winters are predictably cold, is controlled both by genetic and by environmental factors (Feder 1990).Stoats are well adapted to climates much colder than New Zealand, and were among a handful of species to survive in Britain throughout the last (Devensian) glaciation (Yalden 1999).Body fat is deposited at several sites in succession, first along the spine and kidneys, then on gut mesenteries, in cavities under limbs, and finally around shoulders.Even very fat stoats thereby retain their tubular shape (King 1989b).In Nearctic populations, long-term geographic variation in size is correlated with climatic variables, but variation in shape is more likely to be related to the history of recolonisation of northern lands from different glacial refugia (Eger 1990).In the Palaearctic, geographical variation in size is more complex and apparently related to the distribution of prey sizes (Erlinge 1987;Meia & Mermod 1992).In New Zealand, there is significant short-term variation in size, due to nutritional conditions during the period from implantation to independence (Powell & King 1997).Growth of young stoats born in beech forest populations after a good seed year, when mice are abundant, is temporarily enhanced.In large samples from Fiordland and Craigieburn collected in the 1970s, the difference was detectable in skull length, which is fixed early, but not in body weight, which is changeable throughout life.