In writing of the three species of weasels, including Mustela frenata, found at Treesbank and vicinity, Manitoba, Norman Criddle and Stuart Criddle (1925:143, 144), in my opinion, correctly explain the killing of more prey than weasels need. "The fact that weasels frequently kill many more animals than they require for immediate use has been universally interpreted as a lust for killing—a supposition which we believe to be quite erroneous. It is true that weasels often kill more than they need, but the surplus is not necessarily wasted because the animals always store it for future use, in much the same way as do badgers, minks or skunks, and with the same object in view as squirrels have in gathering nuts. We have observed many such stores, but as far as our observations go, the habit of killing in excess occurs much more prominently in the late summer and autumn months than in the spring. Indeed, we have no records of excessive spring slaughter and this indicates that the supposedly blood-thirsty habit of weasels is no more a lust for killing than is the woodsman's foresight in providing his larder with meat for the winter months. It should be noted in this connection that members of the weasel family, when undisturbed, do not leave their victims scattered about, but carefully store them away, and in many instances the bodies are buried with earth or taken under ground to preserve them. We suspect that this instinct for preserving food for future use accounts for most of the excessive killing by carnivorous animals instead of this latter indicating an aimless desire for slaughter which would unnecessarily deplete the food supply of the future. This instinct, however, does not seem to be as definite as that of some rodents, and there is no doubt that much of the stored meat decays before it can be utilized."
Criddle and Criddle (1925:146) note that a weasel in the vicinity of Treesbank was carrying a rat [Rattus] and that "Two small punctures in the throat were the only evidence of the manner in which its death had been brought about."
Considerable information has been recorded concerning the food of Mustela frenata and a little information is on record as to kinds of foods not taken that could have been taken. For example, Ingles (1939:253, 254) on May 14, 1938, near Shasta City, California, noted that nestlings of russet-backed thrushes were ignored by an adult weasel and four young weasels which were feeding instead on meadow mice and a mole. Howard (1935:322, 323) records that a weasel in Michigan which carried bits of meat from beef bones on a porch ignored a red squirrel which drew on the same food supply but which retreated to the end of the porch when the weasel appeared. Quick (1944) records that in the winter of 1940 on a 640 acre area in Washtenaw County, Michigan, four resident weasels did not kill any of the 10 rabbits or several pheasants but subsisted on smaller animals. Glover (1943A) thought that M. frenata kills only a few adult cottontails in the wild. To judge from these observations, M. frenata chooses small mammals as prey in greater measure than it does birds or larger mammals.
Records of prey taken, attacked or pursued by Mustela frenata include the following:
Broad-footed mole (Scapanus latimanus).—One was fed on by an adult M. frenata and four young, on May 14, 1939, "near Shasta City," California (Ingles, 1939:253, 254).
Dusky shrew (Sorex cinereus).—A female weasel, at Majestic, Long Island, N. Y., was shot when carrying a Sorex cinereus that had a small hole in the top of its head (Nichols and Nichols, 1935:297-299).
Big short-tailed shrew (Blarina brevicauda).—One was taken from the stomach of a weasel (Hamilton, 1928:249).
Townsend ground squirrel (Citellus townsendii).—Alcorn saw a weasel five miles west of Fallon, Nevada, carrying a squirrel (Hall, 1946:192).