Their slender forms enable them to follow their prey to the remotest depths of their retreats, and that all rodents have an abiding horror of them is shown by the effect of a weasel’s appearance. Rabbits, although many times their size, become easy victims, and in one instance when a large rat, which had fought its human captor viciously, was put in a cage with a weasel, it at once lost all its courage and permitted itself to be killed without an effort at defense.
Weasels are wonderfully endowed for their predatory work and are undoubtedly the most perfectly organized machines for killing that have been developed among mammals. Their keen eyes are constantly alert to observe everything about them, their ears are attuned to catch the faintest squeak of a mouse or cry of any other small animal, and their powers of scent are very great. When hunting they dart in and out of the holes of rodents, among crevices in the rocks, or through brush piles, pausing now and then to stand upright on their hind feet, the head swaying to and fro as they peer about. The squeak of a mouse starts them instantly in search of it, and like a dog they trail rabbits and other rodents by scent.
As a rule, weasels are terrestrial, but in wooded country they climb trees and leap from branch to branch with all the ease of squirrels. In most localities they are not common, but now and then, where conditions are peculiarly favorable, they become numerous. At one naturalist’s camp in the upper Yukon they were surprisingly abundant, so much so that more than forty were caught in a few days in traps set among broken rocks. There they were extremely bold, hunting for their prey among the rocks within a few feet of the trappers.
The prey of weasels includes almost every kind of small rodent and bird living within their territory. They feed especially upon northern hares, cottontails, conies, ground squirrels, chipmunks, tree squirrels, wood rats, mice, lemmings, quail, ptarmigan, spruce and ruffed grouse, ducks, and numberless other small species. They are also very destructive to domestic fowl, often killing thirty or forty in a night. They unhesitatingly attack rodents many times their own weight.
Once when hunting on the open plain near the southern end of the Mexican table-land, I saw at some distance what appeared to be a brown ball rolling about on the ground. This was soon determined to be a weasel fastened to one of the large and powerful pocket gophers of that region. The weasel had its teeth set in the back of the neck of the gopher, while the latter was blindly trying to tear itself loose. I fired an ineffectual shot at the weasel and it vanished like a flash in the open tunnel of the gopher. As I drew near, the gopher, still in fighting mood, faced me with bared teeth. Later, when I removed its skin, I found that the weasel had torn loose the attachment of the heavy neck muscles to the back of the skull until only a thin layer remained to protect the spinal column. This had been accomplished without breaking the thin, but extremely tough, skin of the gopher.
When a weasel is attacking an animal which resists, like a large ground squirrel, it raises its head and sways its long neck back and forth, its eyes glittering with excitement as it watches for an opening to spring forward and seize its prey. Its attack is always aimed at a vital point, commonly the brain, the back of the neck, or the jugular vein on the side.
Weasels dig their own burrows under the shelter of slide rock, ledges, stone walls, stumps, and outbuildings, or they occupy hollow trees and the deserted burrows of other animals. In nests thus safely located they have one litter containing an average of from four to six, but sometimes numbering up to twelve, young a year. They are born at any time from April to June, according to the latitude. The number of young in a litter is enough to render weasels very abundant, but this is rarely the case, and raises the question as to the influence which holds their number in check.
They are both nocturnal and diurnal, apparently in almost equal degree, since they are frequently observed hunting in the middle of the day, while their nocturnal raids on poultry houses testify to their activities at night. When hunting they appear like sinister shadows and are persistent in pursuit. The young commonly remain with the female until nearly or quite grown and follow her closely on hunting-trips. It is interesting to see a pack of these deadly carnivores working, the mother leading and the young skirmishing on all sides, now spreading out, now closing in, like a pack of miniature hounds. On these family hunting parties, however, they usually keep close to the rocks, logs, brush, or other cover.
Themselves subject to the law of fang and claw, weasels are killed and eaten by wolves, coyotes, foxes, and various birds of prey. Their very lack of fear perhaps in many cases leads to their destruction.
These representatives of the primitive woodland life continue to occupy practically all of their original range. They visit farms in all parts of the country and I have seen them near the outskirts of Washington.