Criddle and Criddle (1925:143, 146) say that weasels drinking at a bird trough "held their mouths very close to the water and as far as we could see, lapped the liquid up with rapid movements of the tongue. As a rule, after drinking, they would merely spring to the ground and vanish amid a bunch of scolding birds, but occasionally we have seen an animal slowly drag itself through the water and follow this performance by some rapid gambols, or a quick run, a method of drying which most of us have practiced in our youth." According to Hamilton's (1933:332) observations on captives, "Weasels are great drinkers, and while they take but little at a time, about 25 c.c. is drunk by a large animal during a day. . . ."
Philip L. Wright's several papers (1942A, 1942B, 1947, 1948A, and 1948B) reporting on his detailed studies of _Mustela frenata_ (subspecies _oribasus_ and _longicauda_) in captivity have yielded a large share of the precise information that we have concerning breeding and reproduction in this species. He has found that a single litter, of up to 9 young is born in the spring, usually in April. At three months of age the females "are full grown." The young males remain sexually immature during the first summer but the young females, as well as the females which are more than a year old, come into heat in the midsummer and are bred by the adult males. After a long period of quiescence lasting for several months, the embryos resulting from these matings become active in early spring and develop to full term in less than 27 days after they become implanted. The adult males are sexually active from April into August, when the testes are at maximal size and are conspicuous in the scrotum. A gradual regression takes place starting in August and extending into September. By October the testes may be fully regressed and the molt to white may start in this month. The white winter weasel, of either sex, is sexually inactive. The testes of the sexually active male in early spring and late summer are seven to eight times the size of the fully regressed testes. Females which had borne and suckled young were first found to be in oestrus 65 to 104 days after birth of the young. Lactation lasts for approximately 5 weeks. In 18 litters the length of the gestation period varied from 220 to 337 days with an average of 279 days. The female in heat has the vulva much swollen and she will remain in this condition for several weeks if not bred. Wright (1948A) describes the actual mating as beginning with a scuffle after which the male grabs the female by the scruff of the neck with his teeth and holds her until she becomes subdued when he clasps her lower abdomen with his front feet and arches his back over her posterior regions. The two animals remain locked in this position usually for two hours and sometimes for longer than three hours. If the animals are left together, copulation may take place again on the same day or upon succeeding days.