In commenting on the economic role of the long-tailed weasel in Manitoba, Criddle and Criddle (1925:145) write as follows: "Supply and demand are prominent factors in governing our weasels' food habits. The two smaller species, as we have already pointed out are so dependent upon mice for a living that they increase or diminish with the fluctuation of these creatures. The Long-tailed Weasel, however, is not so easily checked by the temporary disappearance of any particular kind of game. If mice are scarce it devotes greater attention to gophers or bush rabbits and if these are not in sufficient numbers to satisfy its appetite, the animal raids a poultry house as a last resource. In nine years out of ten, this weasel will find sufficient food about the fields and woods, but on the tenth it may be obliged to temporarily turn to domestic animals. It is at such times that the weasel is seen and its deeds recorded. A thousand mice may have been killed in the meantime, but the destruction of half a dozen hens is alone used as evidence of the weasel's economic standing.
"In the last twenty years we have permitted weasels to frequent the farm buildings at will and the poultry house has been no exception. In that time rats and mice suffered severely from the weasels, while the total number of poultry taken were six. Many times that number, however, have been killed by rats.
"When we review our experiences of the past, we are astonished to find what few poultry have been killed by weasels. Our own losses in forty-two years have not exceeded fifteen birds and even these were usually eatable. There have been reports of losses from time to time from neighbors, but on looking into details we find that there are very few farmers who have experienced more than three separate occasions of weasel depredation and the total loss per farmer in the last thirty years does not, we are sure, exceed ten birds. This is surely a remarkably small payment to weasels in general for the great good done by them in killing rodents.
"We wish to point out, too, that only the exceptional weasel becomes a poultry killer. In most cases apparently it is a fully-grown male that does the killing. There are exceptions, of course, but when we see a large weasel actively engaged in rodent hunting within a few feet of a brood of newly hatched chickens and not even looking at them, we must at least pause to ask if this animal is the enemy that we were taught to believe it to be."
A suggestion that weasels sometimes obtain the prey killed by hawks is offered by Criddle and Criddle (1925:147) who write: "Hawks are not always the aggressors, as is shown by an incident reported by Mr. H. L. Seamans, of Lethbridge, Alberta. Mr. Seamans noted a large buzzard suddenly fly straight upwards from a fence post, and then alight upon another one some distance away. A little while afterward this bird once more arose in the same manner as before, and presently repeated the performance again. An investigation then followed and revealed that a Long-tailed Weasel was following the hawk from post to post.
"We should hardly expect a weasel to attempt to capture a bird of the above type. On the other hand, it is possible that these animals might be able to startle a hawk sufficiently to cause it to drop its prey, which would thus provide food for the weasel."
The following frequency index is compiled from the foregoing data on prey of Mustela frenata.
| Moles (family Talpidae), 5 Shrews (family Soricidae), 26 Pigmy weasel (Mustela rixosa), 1 Ground squirrels (genus Citellus), 23 Chipmunks (genus Tamias), 38 Tree squirrel (possibly all Tamiasciurus), 8 Flying squirrel (genus Glaucomys), 1 Pocket gophers (family Geomyidae), 34 Mice (order Rodentia), 96 Harvest mice (genus Reithrodontomys), 36 Grasshopper mouse (genus Onychomys), 1 Deer mice (genus Peromyscus), 235 Cotton rat (genus Sigmodon), 2 | Wood rats (genus Neotoma), 14 Meadow mice (genus Microtus), 248 Muskrat (genus Ondatra), 1 Old World rats (genus Rattus), 19 House mouse (genus Mus), 1 Jumping mouse (genus Zapus), 5 Varying hare (Lepus americanus), 5 Rabbits (genus Sylvilagus), 48 small birds, 32 chickens, 17 lizard, 1 snakes, 4 insects, 3 |