Part 10

Capitalized color terms, unless otherwise indicated, refer to Ridgway's (1912) _Color Standards and Color Nomenclature_. Some use is made of color terms taken from Oberthür and Dauthenay (1905) because those authors show a much larger number of shades between dark brown and black than does Ridgway (1912). The colors of the upper parts of most weasels are some shade or other of dark brown. Color terms that do not have the initial letter capitalized do not refer to any one standard and consequently are used in a general sense.

Relative extents of the color of the upper parts and underparts are computed from measurements of the circumference of the body at the place where the color of the underparts is narrowest. Ordinarily this place is in the lumbar region rather than in the thoracic region.

An explanation of how cranial measurements were taken is given on page 417. In designating teeth, capital letters are used for teeth in the upper jaw and lower case letters are used for teeth in the lower jaw. For example: I2 denotes the second incisor tooth in the upper jaw and i2 denotes the second incisor tooth in the lower jaw; C1 and c1 refer to the canine tooth of the upper jaw and lower jaw, respectively; P3 and p3 refer to the third premolar of the upper jaw and lower jaw, respectively, bearing in mind that the first (anterior) premolar is absent in the lower jaw and upper jaw of weasels (see fig. 31 on page 416), as also, in some kinds of weasels, is the second premolar; M1 and m1 refer to the first molar of the upper jaw and lower jaw respectively.

In describing the skull and teeth the two sexes are treated separately because differences in shape as well as size are the rule. Unless otherwise indicated, the skulls on which descriptions are based are of adults. Weights of skulls include the weight of the lower jaws. In general, every second subspecies is described. For a subspecies geographically next adjacent to the one described, only the differences between the two are enumerated. This method of description indicates also likenesses and is more economical of words than some other methods of description. Also, by use of this method, cross reference is reduced to one other subspecies. Following this formal description, there is a comparison of the cranial and dental characters with those of geographically adjacent subspecies.

In the paragraph headed "Remarks" the two words "character" and "structure" frequently appear. The word structure here is used to mean some part of an animal, as for example, a hair, a muscle, a bone, or an internal organ. A structure is not a system, as for example, the digestive system or osseous system. A character is some weight, linear dimension, volume, shape, color, or other perceptible attribute of a structure, of a system, or of an entire organism.

In recording the localities of capture of specimens examined, effort has been made to be exactly as precise as the locality data on the labels of the specimens permit. The word "County" is written out in full when the name of the county is written on the label of each specimen listed from that county. When one specimen, or more, here assigned to a given county lacks the name of the county on the label, then the abbreviation "_Co_." is used. The surprising frequency with which the same place name is repeated in a given state or province makes it desirable for the collector to write the name of the county, or corresponding minor political subdivision, on labels of study specimens at the time they are prepared.

SYSTEMATIC ACCOUNTS OF SPECIES AND SUBSPECIES

=MUSTELA ERMINEA= Linnaeus

Ermine

(Synonymy under subspecies)

_Type._--_Mustela erminea_ Linnaeus, Systema Naturae, 10th ed., p. 46, 1758.

_Range._--From the British Isles and Atlantic Coast of Europe across Eurasia and North America including Greenland, from the northernmost land, south, in North America, to the lower margin of the Canadian Life-zone; geographically south to Connecticut, New York, Pennsylvania, northeastern Ohio, southern Michigan, Wisconsin, northern Iowa, Minnesota, North Dakota, in the Rocky Mountains to northern New Mexico, in the Sierra Nevada to Mono County, California, and on the Pacific Coast to the Golden Gate.

_Characters for ready recognition._--Differs from _Mustela rixosa_ in presence of black pencil on tail, tail-vertebrae more than a fourth of length of head and body, and in regions where the two species occur together, basilar length of skull more than 32.5 in males and more than 31.0 in females; from _Mustela frenata_, in regions where the two species occur together, by tail less than 44 per cent of length of head and body and by postglenoidal length of skull more than 46 per cent of condylobasal length in males and more than 48 per cent in females.

_Characters of the species._--Size medium to small (total length 225 to 340 mm. in males and 190 to 290 mm. in females); tail 30 to 45 per cent of length of head and body, with distinct black pencil; caudal vertebrae 16 to 19; skull with long braincase and short precranial portion; postglenoidal length, when expressed as a percentage of the condylobasal length, more than 48 in females and ordinarily more than 46 in males; upper parts brown; underparts whitish, ordinarily continuous from chin to inguinal region but in subspecies in the humid region along the Pacific Coast interrupted in some individuals by brown of upper parts encircling body in the abdominal region. The soles of the feet in each of the subspecies are densely haired in winter and have only a relatively small area of the foot-pads exposed in summer, the intervening areas being well haired even at that season. The uniformity throughout the species as regards hairiness of the foot-soles and also the character of the vibrissae makes it unnecessary to describe these features in the accounts of the subspecies of _erminea_.

_Geographic variation._--In the Old World 16 or more subspecies are currently recognized and there are 20 in North America. The features in which geographic variation is especially prominent are: First, size, as expressed by external measurements and weight, second, color pattern, depending on the extent, in relation to one another, of the dark-colored upper parts and light-colored underparts, and third, breadth and depth of the rostral region of the skull. Except in size, the variation in the skull is less than in _M. frenata_. Likewise in tone and shade of upper parts and hue or tint of underparts, _erminea_ is less variable than _frenata_ and has the face all of one color without the contrasting color-pattern of the face and head seen in many subspecies of _frenata_. _M. erminea_ exceeds _frenata_ as regards variation of the size of the area occupied by the light-colored underparts. At one extreme is the subspecies _arctica_ in which the area of the light color extends well up on the sides of the body, down the insides of the legs, over the feet and far out on the lower side of the tail whereas at the other extreme are the races _streatori_ and _olympica_ in which the light-colored underparts are restricted to two areas, one on the chin, throat and chest, and the other on the inguinal region. These areas may or may not be connected by a thin line of white color along the midline of the underparts. In size of animal, _erminea_ probably exhibits the maximum variation among American species of weasels; an average-sized male of the race _arctica_ weighs 4 times as much as one of the race _muricus_, and in the species _frenata_ I doubt that the difference is quite as great between individuals of the smallest race, _effera_, on the one hand, and either of the largest races, _texensis_ or _macrophonius_, on the other hand although actual weights are not available for these races of _frenata_. As elsewhere indicated, the small-sized individuals of _M. erminea_ are of the southern races and the large-sized individuals are of the northern races. This decrease in size southward occurs both in Asia and in America.

_Natural history._--habitat and numbers.--Along the International Boundary east of the Turtle Mountains, Soper (1946:136) found this species present only in timbered areas and absent from many untimbered areas. Of the same species to the westward he comments "so far as I know at present, there is no evidence to show that any short-tailed weasels inhabit a broad strip of treeless territory immediately north of the International Boundary in Canada from southwestern Alberta to southeastern Saskatchewan." The same author (1942) reports that in the general area of Wood Buffalo Park, Northwest Territory, south of Great Slave Lake, the ermine is uncommon on pine-grown sand ridge and rolling upland and common in lower spruce-aspen parklands, stream-side coniferous belts, and grassy, semi-wooded swamplands.

Nine ermines per square mile is the number that Soper (1919:46-47) estimated at Edmonton on the basis of the numbers that he trapped there in the winters of 1912-13 and 1913-14 and on the basis of the tracks of remaining ermines. From corresponding data he estimated the population in the winter of 1913 on the Hay River, north of Jasper Park, to be nine per square mile. In each of these instances he estimated ten weasels per square mile but he inclined to the view that one-tenth of the animals involved in his counts were long-tailed weasels (_Mustela frenata_). Osgood (1909B:30) and his field companion in the period July 31 to September 3, 1903, took a series of 42 specimens within a radius of 500 yards of their camp at the head of Seward Creek, Alaska, all caught in four traps, in one month. Of the 42 specimens, 28 are males and 14 are females.

Fluctuations of a multiannual nature are marked in this species. Bailey (1929:156) observes that in Sherburne County, Minnesota, when meadow mice are abundant for two or three years these weasels become abundant but that when the mice are scarce the weasels also become scarce. Manning (1943:56), on Southampton Island, noted "that the maximum and minimum points of the weasel cycle are much more sharply marked than those of the fox cycle and the increase and decrease are more rapid."

How far an ermine will travel in a given length of time has seldom been recorded but Hamilton (1933:293), on March 20, 1932, "followed the track of a small weasel, presumably a male _cicognanii_, for four miles in the fresh snow," and Ingles (1942) observed a diminutive ermine of the subspecies _M. e. muricus_, at Woods Lake, California, 286 yards from its den.

Behavior

As regards locomotion, Soper (1919:46), in reference to _Mustela cicognanii_, presumably in Ontario, Canada, writes that in the bounding gait the hind feet register almost, if not exactly, in the front-foot impressions, with the right front and hind feet lagging slightly behind. "The distance normally is about 19 inches, representing a regular rate of travel. . . . In traversing open spaces they resort to long, graceful leaps upwards of six feet in length. . . . I measured a record . . . of 8 feet, 2 inches."

Of _M. e. arctica_, Dice (1921:22) writes that when it runs "the tail is carried off the ground usually at an angle of about 45 degrees." Seton (1929 (2):598) states that "At Carberry [Manitoba] I have often seen this energetic little creature seeking for Mice in the deep, soft snow. Its actions are much like those of an Otter pursuing salmon. Sometimes it gallops along a log, or over an icy part of the drift; then plunges out of sight in a soft place, to reappear many yards away. . . ."

Little is recorded concerning swimming but on this score Seton (1929 (2):602) does quote J. W. Curran, who in July, 1899, at Lake Couchiching, Ontario, watched an ermine pursue a chipmunk into the water and for 100 yards before giving up the chase and wheeling around and making for shore. In swimming "The Weasel, I think, showed more of his body, and seemed to exert himself more" than the chipmunk.

As to voice, Dice (1921:22), at Tanana, Alaska, heard the ermine, when excited, bark somewhat like a mink but not so loud and Seton (1929 (2):606) quotes Manley Hardy to the effect that the species has a purring note.

Sense of smell was used by an _M. e. muricus_ that Dixon (1931:72) watched as the ermine followed a three-fourths-grown pika. Concerning the ermine at Carberry, Manitoba, Seton (1929 (2):598-599) writes that "The smell of blood must be as far-reaching as it is attractive to these sanguinary little creatures. I have frequently hung new-killed Rabbits and partridges temporarily in trees, and, after an absence, in some cases of a few minutes only, have found an Ermine mauling the game, though there was no sign of such a visitor when the cache was made."

Enemies

George Measham, of Winnipeg, found sign in the snow indicating that a great snowy owl had killed an ermine and T. McIlwraith shot a bald eagle at Hamilton Bay which had the bleached skull of a weasel (probably of this species) clinging to the throat (Seton, 1929 (2):603).

A. B. Howell (1943:98) likens mustelid mammals to domestic cats in their manner of crossing roads and thinks that mustelids loiter at the side of the road until the stimulus of the approaching car causes them to make a dash whereupon they are caught by the wheels and killed. Three of four weasels seen to cross the road were killed, one even having apparently crossed the road before turning back and being killed under the car. One weasel killed was _Mustela erminea cicognanii_. Dalquest (1948:190) in writing of this species in the state of Washington, says "I have seen only one abroad in the daytime. It dashed from a roadside thicket . . . and was crushed beneath the wheels of a car."

Food

The killing of prey is described by Hamilton (1933:332) as follows: "A rapid dash, and the bird or mouse is grabbed over the back of the skull, the fore legs encircle the animal as though hugging it, and the hind legs are brought up to scratch wildly at the captive. . . . If [the prey is] a large animal, as a rat, the weasel usually lies on its side, while the diminishing struggles of the rodent continue, but if a mouse or a small bird [is the object of attack], the weasel is apt to crouch over its prey. Little time is lost over the first [mouse] . . . if two mice are present [;] a strong bite through the brain case . . . [is] sufficient. If only one animal is present, the weasel dawdles over its kill some time after life has departed."

Hamilton's (1933:333) study of the contents of the digestive tracts of bodies of ermines obtained from fur trappers and fur buyers in New York enabled him to publish the following "Frequency Indices of Mammal Genera in Fall and Winter Food of 191 Mustela cicognanii": _Microtus_, 35.7 per cent; mammals undetermined to genus but principally mice, 16.3; _Blarina_, 15.1; _Peromyscus_, 11.4; _Sylvilagus_, 9.0; _Sorex_, 4.9; _Rattus_, 4.4; _Tamias_, 3.6. Close correspondence is shown by the following data of Aldous and Manweiler (1942) for the ermine from Lake of the Woods, Minnesota: mice, 58.7 per cent by number and 54.5 by volume; shrews 22.5 and 21.8 per cent; birds, 2.7 and 5.0 per cent. Of the mice in stomachs, 40 per cent were microtines, 15 per cent were _Peromyscus_ and 45 per cent were unidentified as to kind. Fragments of a small fish were found in one stomach. Summed up, the dominant winter foods were mice and shrews. Trapping of the mammal populations was done to see what the available food was and it was found that the small mammals were eaten in direct ratio to their relative abundance. Snowshoe rabbits and red squirrels were not eaten. The Minnesotan data were from 60 stomachs and 53 intestinal tracts recovered from 129 weasels trapped by use of scent (not bait) mostly from January 1 to February 7, 1939, although a few were trapped in 1938. Analyses of contents from stomachs gave approximately the same results as those from intestines. In 1939 at Lake of the Woods, weasels were concentrated where food was abundant but no such concentration was noted in the following winter.

Big short-tailed shrew (_Blarina brevicauda_).--In New York State, the ermine preys on _Blarina_ as shown by Hamilton's (1933:330) seeing one being carried by a male ermine on May 6, 1931, and another being carried by a female on May 13, 1932. The same author (1928:249) found the remains of a _Blarina_ in a small female from Malone, New York. Kirk (1921) observed, however, that the ermine (_M. e. cicognanii_) avoided the shrew, _Blarina_, caught in a trap and that _Blarina_ avoided the weasel caught in a trap.

Chipmunk (genus _Tamias_).--Remains were found in a male ermine in New York on May 14, 1932 (Hamilton, 1933:330), and Seton (1929 (2):602) records a chipmunk at Lake Couchiching, Ontario, that was pursued into the water by an ermine.

Deer mice (genus _Peromyscus_).--As shown by Hamilton (1933:33) and Aldous and Manweiler (1942), _Peromyscus_ was second only to microtines in numerical abundance among the food items of ermines in New York and Minnesota. _Peromyscus_ and microtine rodents were brought to a den of the diminutive _M. e. muricus_ in early August, in Fresno County, California, according to Ingles (1942). He observed that an Alpine chipmunk was active under and around the tree and that juncos reared young 40 feet from the den but that the chipmunk and juncos were unmolested by the ermines.

Lemming (genus _Lemmus_).--One was recovered from a female ermine (with milk in her glands) at Laurier Pass, British Columbia (Sheldon, 1932:201).

Red-backed mouse (genus _Clethrionomys_).--Criddle and Criddle (1925:146) record that on "May 31, 1921.--Saw a Bonaparte's weasel capture a Red-backed Vole after a long hunt during which the pursuer never once lost track of its victim."

Meadow mice (genus _Microtus_).--As shown by the data of Hamilton (1933:333) and Aldous and Manweiler (1942) recorded above, _Microtus_ is the item of first importance in the diet of the ermine in New York and Minnesota. Criddle and Criddle (1925:146) write concerning the vicinity of Treesbank, Manitoba, that "October, 1918.--Following a severe outbreak of mice in 1916-17, Bonaparte's weasel increased enormously and very soon reduced the rodents to comparative rarity. This resulted in a scarcity of food for the weasels, which in their turn became greatly reduced in numbers."

Old World rat (_Rattus_).--Bishop (1923) found two headless rats near a nest of this species in Albany, New York.

Pika (_Ochotona_).--Dixon (1931:72) at Milner Pass, Colorado, on July 20, 1931, saw an ermine, of the subspecies _muricus_, following a three-fourths grown pika by scent and outrunning the pika. The pikas worked a relay system and the weasel abandoned the trail when the fourth pika became the object of the chase.

Cottontail (genus _Sylvilagus_).--Hamilton (1933:33), as noted above, found remains of cottontail in the digestive tracts of ermine that had been trapped for fur in winter. Possibly these remains were bait that had been placed at traps.

Snowshoe rabbit (_Lepus americanus_).--Morse (1939:210) in a study of predation on hares and grouse in the period of notable decimation of these two game species in 1935-1936 in the Cloquet Valley State Forest, in St. Louis County, Minnesota, found that "weasel predation on hares appeared to be of very low incidence or altogether lacking."

Wild birds (Class Aves).--Aldous and Manweiler (1942), as noted above, found that the remains of birds constituted five per cent by volume of the food of the ermine in winter in Minnesota.

Chicken (genus _Gallus_).--Criddle and Criddle (1925:145), who published relatively extensive data on the three species of weasels of Manitoba, write that: "We have no record of Bonaparte's weasel killing poultry, and we doubt whether it ever does so." However, Soper (1919:46) investigated the excited cackling of a hen brooding chicks at night and found a solitary ermine that had killed three chicks and that had the remainder under very active scrutiny.

Leopard frog (_Rana pipiens_).--One frog was found in a male ermine on November 20, 1931, in New York by Hamilton (1933:300).

Fish (Class Pisces).--Aldous and Manweiler (1942) found fragments of a small fish in one of 60 stomachs of ermine from Minnesota.

Earthworm (Phylum Annelida).--Osgood (1936:64), presumably at Rutland, Vermont, observed a pair of weasels from 2:15 P.M. to 5:00 P.M., in a barn and saw the female in that time make many trips for food for her young. Only earthworms were brought. Fifty traps in an adjacent, swampy field caught only one bull frog and no mice indicating that mice had been eliminated from the foraging territory of the ermine.

In handling food, Dice (1921:22) noted that the Alaskan ermine did not use the feet but only the mouth.

Reproduction

Litters of 4, 4, 7, 7, and 8, yielding an average of 6 young per litter have been recorded from the northeastern United States by Hamilton (1933:327). He (_op. cit._:321-325) described animals one day old from New York State as being flesh-colored, having the long neck of the adult and a fine growth of white hair two millimeters in length, on the dorsal surface of the neck, that foreshadows the mane or pompadour that is prominent from the 14th to the 21st day of life. Six animals, when one day old averaged 1.7 grams in weight, which was three per cent of the weight of an adult female and one and one half per cent of the weight of an adult male. At two weeks of age the heavy brown mane stood out in marked contrast to the rest of the scantily, white-furred animal. The eyes opened on the thirty-fifth day of life.

For rearing their young, ermines live in burrows. Bishop (1923), in Albany, New York, found a burrow occupied by four young and a pair of adults. The burrow had many galleries and contained a nest constructed of rat fur, fine grass and fragments of leaves. At Woods Lake, Fresno County, California, in early August, Ingles observed (1942) some young and at least one adult at their den which was in a burrow beneath a hollow tree. The ermines used the hollow root and the hollow tree as well as the burrow beneath. Seton (1929 (2):591) quotes S. Eldon Percival, of Barretts Rapids, Ontario, as finding the living quarters of an ermine in unthreshed grain stacked in a barn and says (_op. cit._:590) that John Burroughs dug out a nest, composed of leaves and the fur of mice and moles, two or three handfuls in bulk, from a cavity the size of a hat, arched over with a fine network of tree roots.

Four instances in which the male as well as the female was present at a den containing young are cited by Hamilton (1933:328) and he gives some evidence, although not at all conclusive, that "adults customarily pair, or at least run together, at times other than the breeding season." No other writers remark on this matter. I doubt that adult ermines are associated in pairs for most of the year but such may be the case.

=Mustela erminea arctica= (Merriam)

Ermine

Plates 2, 3, 4, 9, 10, 11 and 41

_Putorius arcticus_ Merriam, N. Amer. Fauna, 11:15, pl. 2, figs. 1, 1a, and pl. 5, figs. 6, 6a, June 30, 1896.

_Putorius_ (_Gale_) _erminea_, Coues, Fur-bearing animals, p. 109, 1877 (part).

_Putorius richardsonii_, Bangs, Proc. Biol. Soc. Washington, 10:16, pl. 1, figs. 3, 3a, pl. 2, figs. 3, 3a, and pl. 3, figs. 6, 6a, February 25, 1896 (part).