Chapter X: Introduction (9)

"The weasel ate the head and brain first, beginning at the back of the head and working forward. Just before reaching the nose the process was reversed and eating then proceeded from the base of the skull toward the tail of the mouse. The tip of the nose, maxilla with teeth, and the tail seemed to be the parts least preferred; they were not eaten when an abundance of food was present. At no time did the weasel place its front feet on the mouse in an attempt to hold it. A second or third mouse was killed immediately upon being placed in the cage even though the first one had not been consumed. The weasel, however, usually returned to the partially eaten mouse and finished it before starting on a new one. Upon completing a meal, especially if the meal had been particularly bloody, the weasel rubbed its chin on the bottom of the cage, scooting along and appearing more snakelike than normal. Whenever I attempted to remove a mouse, or partially eaten one, from the cage, the weasel hung to the mouse tenaciously, and often allowed itself to be lifted up in this manner.

"In the six days that the weasel was kept in captivity it was fed 10 house mice having a total weight of 118 grams. As no food was given on one day, the amount of food eaten is probably slightly below the actual capacity of the animal. Since the weasel weighed only about 32 grams, the average amount of food eaten a day was slightly in excess of one-half the weight of the animal."

Polderboer (1942:146-147) found in three dens, in Iowa, bits of _Reithrodontomys_ (harvest mice) and _Peromyscus maniculatus_ (deer mouse), and in the digestive tract of one least weasel there was a bone fragment and a few hairs of a deer mouse. In the account, given beyond, of a nest, Criddle (1947:69) records the Pennsylvania meadow mouse (_Microtus pennsylvanicus drummondi_) and the Gapper red-backed vole (_Clethrionomys gapperi_) as prey at Treesbank, Manitoba. The same author, concerning the same place, earlier (1926:199-200) wrote that in 1922 the meadow mouse, _Microtus minor_, "went into winter quarters in great numbers and its homes were well stocked with provisions . . . all went well until the middle of February, 1923. Then, within a few days, each was taken possession of by a least weasel (_Mustela rixosa_) and the inhabitants were quickly destroyed. One dwelling was occupied by one of these weasels for about two weeks during which time I observed that it had dragged several mice over the snow to its temporary home. This residence was examined in April, and in it were discovered six dead _Microtus minor_, one _Evotomys_, the head of another, and at least six or eight remnants of small rodents including _Microtus drummondi_, these last remains being chiefly indicated by the hair-lined nest of the weasel.

"The homes of 27 other vole communities examined at this time were all found to have been entered by weasels, the inhabitants having been killed and partly eaten. Moreover, the weasels had made the homes temporary centers from which they raided other rodent habitations in the vicinity. Thus from being an abundant animal this vole was reduced to insignificance in the course of a few weeks, while all other kinds of mice had suffered severely from the same enemy."

An instance of predation on _Peromyscus_, revealing some of the methods of capturing prey, is recounted by Seton (1929 (2):636-637) who quotes a letter to him from George L. Fordyce, of Youngstown, Ohio, as follows: "While out in the field this morning (Dec. 26), walking along the bank of a ravine at the edge of our golf course, I saw a Field-mouse run out of the bushes into the rough grass that is just outside of the fair-green of the course. In another instant, what I thought at first to be a white Mouse came out at the same place. The Mouse ran into a wheel track, and disappeared under the grass, coming out about 6 feet from where it went in. The white animal followed through the same course, and when it came out, I saw that it was a small Weasel, very little larger than the Mouse, and that it was following the trail of the Mouse by scent.

"For a time the Mouse ran in circles, and zigzagged about, often . . . within 4 or 5 feet of the Weasel; but the latter seemed so intent on the trail, that it did not notice the Mouse to one side. After a time the latter started toward the open golf course; and when the Weasel reached the point where the trail was straight, it sighted the prey, made a sudden dash forward, and, although 25 feet behind, overtook the Mouse while it was going 3 or 4 feet.

"For a few seconds, they seemed to fight, until the Weasel got the Mouse by the throat, and started for the bushes, dragging the body. When it came to within about three feet of me, I moved a little to see what it would do. It dropped its victim, and ran into the ravine. The Mouse had a drop of bright red blood in the center of its white throat. I waited near by for 15 or 20 minutes, thinking the Weasel might come back, but it did not show up again; even an hour later, the Mouse had not been disturbed."

There are two suggestions, but no proof that I know of, in the literature that the least weasel eats insects. Abbott (1884:27-32--1st ed., 1884) gives considerable information on the food (some insects included) of the "little weasel" which he describes (_op. cit._; 27) as having "a little pointed tail of a uniform brown color." Although this suggests _Mustela rixosa_, Abbott mentions on the next page (page 28) that a specimen of the smaller weasel measured six and a half inches from the tip of the snout to the base of the tail and that the tail itself measured two and a fourth inches to the tip of the last caudal vertebra. These measurements indicate that _Mustela erminea_ was involved. Because of the uncertainty as to the species of _Mustela_ involved, Abbott's interesting data on food, nest and behavior are not recorded in the present work. Seton (1929 (2):636) says that of several least weasels brought to D. Nicholson at Morden, Manitoba, most of them decayed so quickly that they could not be saved as specimens. To Seton this indicated that insects were an important part of the food of the weasels.

In summary: Least weasels are known to eat harvest mice, deer mice, meadow mice and red-backed mice; it is suspected that they eat also insects.

Reproduction

Polderboer (1948:296) has taken six specimens in "northeastern Iowa [in] . . . January and December--all males in winter pelage. None of these males showed signs of sexual activity; in all, the testes were retracted and diminutive in size. . . . A male least weasel in brown pelage was taken November 17, 1945, at Marion, Iowa. This specimen had large testes that had descended into the scrotum. The testes, when removed, were about the size of medium-sized garden peas. Microscopic examination of the testes and the vasa deferentia showed mature sperms to be present. . . ."

On July 1, 1917, in Clay County, Nebraska, a nest with four young was found (Swenk, 1926:321). On July 29, 1939, an adult and five young were plowed out of the ground in Allegan County, Michigan; one of the two young males weighed 40.5 grams two days after capture (Allen, 1940:459-460). On August 12, 1932, ten young with the mother, were found in Roseau County, Minnesota (Swanson and Fryklund, 1935:125). September appears to have been the month of birth of a specimen, no. 8472 in the Carnegie Museum, taken on November 24 in Pittsburgh, Pennsylvania. In October, a young least weasel is recorded from Pennsylvania (Winecoff, 1930:313). Early December was the time of birth of a specimen, approximately 10 weeks old, no. 88077, University of Michigan, taken on February 21 in Allegan County. On December 25, 1927, in Washington County, Pennsylvania, "five full-sized, though young . . . animals were caught under the same pile of corn fodder" (Sutton, 1929:253). The first week of January seems to have been the time of birth of a juvenile, no. 88080, University of Michigan, taken in Livingston County, Michigan, on March 27, 1943, since the specimen is approximately seven weeks old. On January 15, 1929, in Washington County, Pennsylvania, four young with the eyes yet unopened were obtained from a nest (Sutton, 1929:254). On January 25, 1928, young, the eyes of which may not yet have been open, were taken from a den in Washington County, Pennsylvania, by Winecoff (1930:313), who records other young having been taken in the same month as well as in February. On March 10, a female from North Portal, Saskatchewan, gave birth to four young (Dunk, 1946:392). On April 18, 1916, four young, half grown, were taken in Nebraska (Swenk, 1926:317). On April 2, 1929, three young were found in Roseau County, Minnesota, according to Swanson and Fryklund (1935:125) who remark that: "The Pennsylvania and Minnesota records show that least weasels may be born any time from July to early February in the northern states." Now, with all of the above records available, it turns out that November, May and June are the only months in which young least weasels have not been reported. Of course some of the young, for which the ages were not specified, were born in preceding months. Even so, the data now available suggests that, in the United States, young least weasels may be born in every month of the year. The number per litter is 3, 4, 4, 4, 5, 5, and 10, yielding an average of 5.

The rate of growth of the young has not been studied enough to allow of judging if it differs significantly from that of other species of the genus. Allen (1940:459-460), however, tells us that of the three young females and two young males captured on July 29, 1939, in Allegan County, Michigan, one male that was killed on July 31, 1939, weighed 40.5 grams. The male remaining alive increased from 46 grams (August 5) to 62.5 grams on September 20, having eaten 63 mice while in captivity. The females in the period of August 5 to September 4 increased in weight as follows: 41 up to 49 grams; 44 to 50 grams; and 47 to 58 grams, having eaten, by September 26, 60, 64 and 65 mice.

Concerning a nest in which young were found, Sutton (1929:254) writes that on January 15, 1929, near Burgettstown, Washington County, Pennsylvania, an animal was seen to enter a small hole in a creek bank. After the observer dug in a distance of approximately six inches an adult, female least weasel was seen and obtained. Back of the animal, the hole, which turned sharply downward, was full of water. The weasel first seen was a female nursing young. A chamber, to the side of the hole, filled with dead grass, comprised a nest containing four young with the eyes yet unopened. Several nests occupied by adult least weasels or by least weasels that were old enough to shift for themselves have been found. Polderboer (1942:145-147) in the winter of 1939-40, on a 144 acre farm in Butler County, Iowa, found four least weasels living, singly, in burrows dug by moles and pocket gophers. The nests therein made by mice were used by the least weasels. Winecoff (1930:312-313) mentions one den in Pennsylvania that contained the remains of only mice, "and not a hint of a feather." Above, in the account of food of the least weasel, Criddle's (1926:199-200) account of the havoc wrought by least weasels among the meadow mice (_Microtus ochrogaster minor_) has been given. In this account he mentions the fur-lined nests of the weasels that had appropriated the homes of the _Microtus_. Criddle's (1947:69) later account of a nest at Treesbank, Manitoba, is as follows: "A Nest of the Least Weasel.--When a least weasel finds its way into a locality that has a large number of mice in it, it selects for its home one of their nests that has been made in a well concealed place. This it immediately starts to improve by lining it with hair plucked from its victims before eating them; and as long as sufficient numbers of mice remain in the district the weasel continues adding their hair to the nest, so that the thickness of its walls give one a good idea of the length of time it has been in use. The nest is not only used for sleeping in, as most of the food is consumed in it. Frozen mice are taken in to be thawed out and the weasel carries those it has recently killed in to prevent them getting frozen, or perhaps to have them warm for its next meal.

"On January 27, 1946, my son Percy called my attention to a nest that he had just uncovered in a clover stack that we were using. This nest had originally been made by a Drummond's vole, _Microtus pennsylvanicus drummondii_, and taken from it by the least weasel, _Mustela rixosa_, the tracks of which had been noticed about the stack yard since the first snow in early November.

"The nest had evidently been in use for at least three months and the continual additions made to its walls had been so great that they were nearly an inch thick of hair matted together so closely that it appeared to be felt. The hair alone weighed nearly 22 gm., so that with this for protection the weasel must have been warm and comfortable through the severest winter weather.

"In the nest were two red-backed mice, _Clethrionomys gapperi_, one of which had the base of its skull eaten out. No hair had been removed from either of them, but a _Microtus_ lying in a side tunnel some feet away had the long hair plucked from its back and sides. In and close about the nest were found forty-three front parts of mice skulls which had evidently been discarded because of the sharp teeth in the maxillaries. Seven full stomachs and eleven hind feet of adult _Microtus_ with parts of leg bones were disclosed in, or under, the weasel's bed and a few small bits of skin with hair attached were scattered among the plucked hair of the nest.

"This weasel seems to have been rather remiss in its sanitary habits as its pile of dung was almost, or quite, touching the nest and only just to the side of its entrance. It was composed of 117 voids all of which contained much hair and broken bone.

"Six other mouse nests found in the same stack, or others adjoining it, had been thinly lined with hair. One of these had two mice in it, a red-backed with its brain eaten out and a _Microtus_ with some hair plucked from its neck. Another nest contained the front part of a skull with teeth and the hind feet and tail of a red-back. Besides the mice found in the nests seven others were discovered tucked away in side tunnels. One of these mice had most of the hair plucked from its back. Whether all these mice and nests belonged to the same weasel or not I am unable to say, but it is usual for them to have several nests in the area surrounding the one that is used as their headquarters or home."

=Mustela rixosa eskimo= (Stone)

Least Weasel

Plates 14 and 15

_Putorius rixosus eskimo_ Stone, Proc. Acad. Nat. Sci.
Philadelphia, 1900:44, March 24, 1900.

_Putorius (Gale) vulgaris_, Coues, Fur-bearing animals, p. 102,
1877 (part).

_Putorius rixosus Bangs_, Proc. Biol. Soc. Washington, 10:21,
February 25, 1896 (part); Merriam, N. Amer. Fauna, 11:14, June
30, 1896 (part).

_Mustela rixosa eskimo_, Miller, U. S. Nat. Mus. Bull., 79:96,
December 31, 1912; Swenk, Journ. Mamm., 7:327, November 23, 1926;
Hall, Univ. California Publ. Zoöl., 30:421, March 19, 1929.

_Type._--Female, age in question, no. 848 in Acad. Nat. Sci.
Philadelphia; Point Barrow, Alaska; July 25, 1898; obtained by E.
A. McIlhenny. Type not seen by me.

_Range._--Alaska and Yukon Territory. See figure 28 on page 180.

_Characters for ready recognition._--Differs from _M. r. pygmaea_
of eastern Asia in longer tail, averaging 11 rather than 16 per
cent of length of head and body, and in study skins reaching only
to heel instead of to point between heel and toes; from _M. r.
rixosa_ in shorter tail averaging 16 rather than 19 per cent of
length of head and body and not extending beyond outstretched hind
feet in study skins; white of underparts extending dorsally as a
reëntrant angle from upper lip to behind eye, rather than
delimited dorsally by a boundary between white and brown color
that extends straight across cheeks from upper lip to side of body
well below eye and ear; breadth of rostrum measured across
lacrimal processes more, instead of less, than 85.5 per cent of
orbitonasal length; from _M. erminea_ of same region by basilar
length of skull less than 32; tail less than 50 and lacking black
pencil.

_Description._--_Size._--Male: The original describer lists
measurements of topotypes as follows: Total length, 204, 230;
length of tail, 28, 31; length of hind foot, 20, 22. Allowing 5
per cent for shrinkage, the hind feet of 5 topotypes yield an
average measurement of 23 for the hind foot.

Female: Measurements of two topotypes are: Total length, 184, 180;
length of tail, 25, 25; length of hind foot, 24, 18. In four other
topotypes the hind feet, allowing 5 per cent for shrinkage, yield
an average of 21.

_Color._--Winter pelage all white, rarely with few white hairs in
tip of tail but no black pencil; summer pelage with upper parts
about Raw Umber and tone 3 of Chocolate pl. 343 of Oberthür and
Dauthenay; underparts white, extending over upper lip, insides of
limbs and over all four feet. Line of demarcation between
underparts and upper parts extends from upper lip posterodorsally
to behind eye down to base of ear, up behind ear for a third or
more of its height, and back along side of body. Tail unicolor all
around and same color as upper parts. Least width of color of
underparts averaging 83 per cent of greatest width of color of
upper parts.

_Skull._--Based on topotypes; see measurements and plates 14 and
15; weight, 0.82 (0.74-0.93) grams in males, and 0.80 and 0.84 in
two females; basilar length, 29.5 (27.6-30.1) in males and 27.8
(27.1-28.8) in females; otherwise as described in _M. e.
richardsonii_.

_Remarks._--Among the earliest specimens preserved was one by Edward W. Nelson in the course of his explorations of the Upper Yukon, and one in 1874 by L. T. Turner from St. Michaels, Alaska. Bangs, in 1896 (p. 22) mentioned the occurrence of the species in Alaska, but it was not until 1900 (p. 44) that Stone named the subspecies, and then principally on the basis of specimens obtained two years before by E. A. McIlhenny.

The large size, broad skull, light color and short tail are the distinguishing subspecific characters of the race _eskimo_, and the three characters first mentioned are distinguishing features also of the subspecies of _Mustela erminea_, namely _arctica_, which inhabits the same region. Possibly _eskimo_ also will be found on Banks Island and the other Arctic islands between Alaska and Greenland, as is _M. e. arctica_; at the present time no specimens of _Mustela rixosa_ are known from these islands although some race of rixosa would be expected to occur there.

Animals from southern Alaska average slightly smaller than those from northern Alaska, and this decrease in size toward the south probably represents intergradation with _M. r. rixosa_. Further evidence of intergradation is furnished by the short tail of the specimen from 15 miles east of Atlin; in other particulars this specimen agrees with the subspecies _rixosa_ to which it is here referred. Nevertheless, the short tail, and color pattern, namely reëntrant angle of white behind the eye, is to be seen in all Alaskan specimens examined in the brown pelage, even in no. 107591, from Tyonek on Cook Inlet, which Osgood (1901:69) and Swenk (1926:323) thought might not differ from the subspecies _M. r. rixosa_.

Each of four male topotypes, hardly subadult in age, probably of a single litter, is much larger than any other specimen seen from Point Barrow. The basilar length, for example, is 31.9 as against 29.5, and the weight of the skull (with lower jaws) is as much as 1.5 grams, as against 0.93 in the heaviest of the other males. Initial examination of materials from Point Barrow raised the suspicion that two distinct species were represented--_rixosa_ and a larger one possibly allied to _M. nivalis_ of the Old World. Nevertheless, further study almost completely allayed the suspicion because the only difference discernible is one of size, and it is supposed that additional specimens will bridge the gap in size and show that _M. r. eskimo_ at Point Barrow averages larger than the adult specimens now available indicate. The four large males of subadult age are nos. 42814-42816 and 42818 of the American Museum of Natural History.

Of the fourteen adult and subadult skulls examined, two display lesions resulting from infestation of the frontal sinuses by nematode parasites. None of the young skulls show such infestation.

_Specimens examined._--Total number, 42 as follows. Arranged
alphabetically by Territory and District and unless otherwise
indicated in the United States National Museum.

=Alaska.= Barrow and Point Barrow, 19 (8[2] 7[74], 2[1], 1[50]);
Wainwright, 1[57]; Mts. back of Icy Cape, 1[77]; west of Beechey
Point, 1[2]; west edge of Colville River Delta, 1[2]; Koyukuk
River, 16 mi. above Beetles, 1; upper Yukon, 1; Fort Yukon, 1;
Stephens Village, 1; Wales, 1[57]; McDonald Creek, tributary of
Salcha Slough, 1; near head of Toklat River, 1; head of Kantishna
River, 1; St. Michael, 4 (2[74]); Tyonek [= Tyonek], 1; Bethel, 3;
vic. Bristol Bay, 1.

=Yukon.= La Pierre's House, 1; Klotassin River, tributary of White
River, 1.

=Mustela rixosa rixosa= (Bangs)

Least Weasel

Plates 14 and 15

_Putorius rixosus_ Bangs, Proc. Biol. Soc. Washington, 10:21, pl.
1, fig. 6, pl. 2, fig. 6, pl. 3, fig. 4, February 25, 1896;
Merriam, N. Amer. Fauna, 11:14, pl. 2, figs. 7, 7a, June 30,
1896.

_Putorius pusillus_, Baird, Mamm. N. Amer., p. 159, 1858.

_Putorius (Gale) vulgaris_, Coues, Fur-bearing animals, p. 102,
1877.

_Mustela rixosa_, Thomas, Proc. Zoöl. Soc. London, p. 168, March,
1911.

_Mustela rixosa rixosa_, Miller, U. S. Nat. Mus. Bull., 79:96,
December 31, 1912; Swenk, Journ. Mamm., 7:327, November 23, 1926.

_Type._--Female, adult, skin and skull; no. 642 Bangs Coll. in
Mus. Comp. Zoöl.; Osler, Saskatchewan; July 15, 1893; obtained by
W. C. Colt; original no. 79 according to describer.

The skull lacks the basioccipital, basisphenoid, and left
zygomatic arch. The "crowns" of the lower canines are missing;
otherwise the teeth are present and entire. The skin is fairly
well made, with soles of hind feet up, in good condition and in
summer pelage.

_Range._--From northern British Columbia and Great Slave Lake
south on the west side of the Rocky Mountains to Ootsa Lake,
British Columbia, and on the east side of the Rocky Mountains,
south to central Montana, North Dakota and Minnesota; eastward in
Canada, entirely north of St. Lawrence River, to Atlantic Ocean.
See figure 28 on page 180.

_Characters for ready recognition._--Differs from _M. r. eskimo_
in longer tail averaging 19 rather than 16 per cent of length of
head and body and extending beyond outstretched hind feet in study
skins, rather than to a point short of tips of toes; boundary
between brown upper parts and white underparts extending straight
across cheeks from upper lip to side of body well below eye and
ear, rather than with reëntrant angle from upper lip carrying
white upward to point behind eye, and with breadth of rostrum
less, instead of more, than 85.5 per cent of orbitonasal length;
from _M. r. campestris_ by smaller size: hind foot less than 25 in
males and ordinarily less than 22 in females; in males total
length less than 216 and tail averaging less than 34, and in
females total length averaging less than 182 and tail averaging
less than 29; color said to average darker; from _M. r.
allegheniensis_ by three average differences, namely lighter
color, longer tympanic bullae and larger size of males; from _M.
frenata_ and _M. erminea_ of same region by basilar length of
skull less than 32; tail less than 50, and lacking black pencil.

_Description._--_Size._--Male: Six adults and subadults from
Shaunavon, Saskatchewan, yield average and extreme measurements as
follows: Total length, 202 (188-208); length of tail, 32.5
(31.5-34.0); length of hind foot, 22.8 (21-24).

Female: One adult and 3 subadults from the same area yield average
and extreme measurements as follows: Total length, 172
(162-190.5); length of tail, 27.4 (24-34); length of hind foot,
19.6 (17.5-22).

_Color._--Winter pelage all white, rarely brown; as described in
_M. r. eskimo_ except that line of demarcation on side of head
between upper parts and underparts passes almost straight back
without the dorsally directed reëntrant area of white behind the
eye and ear; least width of color of underparts averaging 52 per
cent of greatest width of color of upper parts.

_Skull_ (Based on those from Shaunavon, Sask.)--See measurements
and plates 14 and 15; weight, 0.88 (0.70-0.98) grams in males and
0.55 (0.54-0.56) in females; basilar length, 29.5 (28.4-30.4) in
males and 26.1 (24.7-27.0) in females; otherwise as described in
_M. e. richardsonii_.

_Remarks._--As early as 1858 (p. 159) Baird recognized an individual of this race from Pembina, Minnesota, as pertaining to a distinct species. Although he used for it the specific name _pusillus_ originally proposed by DeKay for a small weasel from the state of New York, Baird wisely noted that the specimen he described "may be different from the New York species. . . ." After preparing this account, Baird included a second specimen, from Fort Steilacoom, Washington Territory, which he thought might be the same, but the differences that he was careful to point out, in the light of later knowledge, show it to be of the species _Mustela erminea_. Only a few other naturalists followed Baird in distinguishing the least weasel as a separate species until Bangs in 1896 (p. 21) clearly differentiated it and proposed for it the name _Putorius rixosus_, which continues in use today and applies to the species.

The accumulation at the National Museum of Canada, through the energy of Dr. R. M. Anderson, of a good series of specimens from Saskatchewan in the general vicinity of the type locality allows for the first time an adequate conception of the amount of secondary sexual variation and individual variation and permits recognition of subspecific characters to differentiate between _M. r. rixosa_ and the subspecies _eskimo_ and _campestris_. In comparison with the subspecies _allegheniensis_ the basis for segregation is less clear and will remain somewhat in doubt until additional adults of _allegheniensis_ from, say, Pennsylvania, become available with accurate external measurements taken in the flesh and especially with complete skulls.

Intergradation with the subspecies _eskimo_ is suggested by the short tail of the specimen from fifteen miles east of Atlin, British Columbia; in other particulars that specimen, a skin-alone, agrees with the subspecies _rixosa_. Intergradation with _campestris_ is indicated by increased size of some specimens from North Dakota, and is suggested with _allegheniensis_ by the color of specimens from Wisconsin and Illinois. Three specimens from Winona County, in southeastern Minnesota, unfortunately are skulls-alone without external measurements. Also, two of these skulls are of young animals. The one adult, unsexed, is from Crystal Springs. Selected cranial measurements are: basilar length, 28.5; length of tympanic bulla, 10.9. These measurements accord with those of males of the subspecies _rixosa_ to which the specimens from Winona County, therefore, are here assigned. The possibilities have not been excluded, however, that the adult is an unusually large female of the subspecies _campestris_ or a male of _allegheniensis_ that has tympanic bullae longer than average for that subspecies.

Some hesitation is felt in assigning the specimens, 8 in all, from eastern Canada to the subspecies _rixosa_. The skin-alone from Eagle River and the skin, with part of the skull, from St. Michael Bay, are in transitional pelage and are of no help in appraising subspecific characters. The one adult specimen which does have a complete skull is from an island south of the Comb Hills. This animal in all respects agrees with selected individuals of _M. r. rixosa_ from Saskatchewan, but each of the five other skins in summer pelage has spots of dark brown color on the breast. Only about one specimen in three of _rixosa_ from Saskatchewan is similarly marked. Furthermore, on some of the specimens from eastern Canada the spots are larger than on any of the animals from farther west. The greater frequency of brown spots on the breast, the larger average size of these spots, and the darker average coloration of the upper parts are suggestive of geographic variation, the existence of which has to be proved by additional and more complete specimens from eastern Canada. For the time being, specimens from there are tentatively assigned to the race _rixosa_.

Of 56 subadult and adult skulls only 3 (1 North Dakota; 1 Calgary, Alberta; and 1 Island S Comb Hills, Queb.) display lesions resulting from infestation of the frontal sinuses by nematode parasites. None of the young skulls shows such infestation.

_Specimens examined._--Total number, 87 as follows. Arranged
alphabetically by provinces and states and within each from north
to south. Unless otherwise indicated, specimens are in the United
States National Museum.

=Alberta.= Miette River, 1[77]; 5 mi. NW Camrose, 1[77]; Camrose,
2 (1[77], 1[31]); "near Camrose," 2[77]; Forks Blindman and Red
Deer rivers, 1[60]; Innisfail, 1[86]; Veteran, 1[93]; Diddsbury [=
Didsbury], 1; Calgary, 2 (1[93], 1[2]); Shepard, 1[86].

=British Columbia.= Clarks Ranch, Halfway River, Peace River Dist,
1[85]; 15 mi. E Atlin, 1[8]; Wistaria, P. O., 3 (2[77], 1[85]);
Ootsa Lake, 1[85].

=Labrador.= Davis Inlet, 1[60]; 30 mi. upriver and 20 mi. toward
Groswater Mts., Eagle River, 1; St. Michael Bay, 1.

=Mackenzie.= Old Fort Reliance, 1[2]; Fort Resolution, 2; Fort
Smith, 1.

=Manitoba.= Gypsumville, 1[86]; Lake St. Martin Reserve, 1[86].

=Minnesota.= _Roseau County_: Cedarbend, 2[14]; Grimstad, 1[14];
America, 2 (1[14], 1[74]); Malung, 1[74]; Norland, 1[41]; Falun, 3
(1[14], 1[74], 1[41]); Palmville, 1[41]; Spruce, 1[74]; Stokes,
1[74]. No locality more definite than Marshall County, 1[14].
_Clay County_: Moorhead, 1[36]. _Winona County_: "near" Whitman,
1[34]; Altura, 1[98]; Crystal Springs, 1[98].

=Montana.= Sun River Valley, 1; Wibaux in Wibaux County, 1.

=North Dakota.= _Walsh County_: Grafton, 15 (3[60], 1[93], 5[2],
2[14], 1[74], 1[1], 1[76]). _McHenry County_: 4 and 4-1/2 mi. N
Upham, 2. _Wells County_: 1[36]. _Morton County_: Mandan, 1[60].

=Ontario.= Algoma Dist: Tatnall, near Oba, 1[86]. Moose Factory,
1[75].

=Quebec.= Island S of Comb Hills, James Bay, 1[9]. _Saguenay
County_: Natashkwan, 1.

=Saskatchewan.= Osler, 1[75]; "near Regina," 1[77]; Dollard,
2[31]; Shaunavon (and "near" and 1 mi. NE), 9[77]; Klintowel P. O.
(about 15 mi. N of Eastend), 1[77]; Eastend and "near" Eastend,
2[77].

=Mustela rixosa allegheniensis= (Rhoads)

Least Weasel

Plates 14, 15 and 41

_Putorius allegheniensis_ Rhoads, Proc. Acad. Nat. Sci.
Philadelphia, 1900:751, March 25, 1901.

_Putorius rixosus allegheniensis_, Cory, Mamm. Illinois and
Wisconsin, p. 378, 1912.

_Mustela allegheniensis_, Miller, U. S. Nat. Mus. Bull., 79:96,
December 31, 1912.

_Mustela rixosa allegheniensis_, Swenk, Journ. Mamm., 7:328,
November 23, 1926.

_Type._--Probably male adult, skin and skull, no. 6195, Acad. Nat.
Sci. Philadelphia; near Beallsville, Washington Co., Pa.; about
1885 or 1886; obtained by Robert Hawkins.

Type not seen by me.

_Range._--Wisconsin, northern Illinois, northern Indiana,
Michigan, Ohio, Pennsylvania east to Dauphin County and south in
the mountains to northwestern North Carolina. See figure 28 on
page 180.

_Characters for ready recognition._--Distinguished from _M. r.
rixosa_ by three average differences, namely, darker color,
shorter tympanic bullae, and smaller size of males; from _M. r.
campestris_ in smaller size: hind foot less than 25 in males and
less than 22 in females; in males total length less than 216 and
tail averaging less than 34, color averaging darker; from _M.
frenata_ and _M. erminea_ of same region by basilar length less
than 31, tail less than 45, and lacking black pencil.

_Description._--_Size._--Male: An adult or subadult from Fair
Oaks, Pa., a subadult from Finleyville, Pa., and an adult from
Huttonsville, W. Va., measure, respectively as follows: Total
length, 206, 194, 191 (average 197); length of tail, 37, 32, 28
(32); length of hind foot, 23 in each. An adult from Roanoke,
Indiana, weighs 40.6 grams.

Female: Two young from Leasuresville, Pa., and Middle Paxton
Twp., Pa., measure, respectively, as follows: Total length, 188,
172; length of tail, 33, 30; length of hind foot, 20.5, 21. An
adult from Monroeville, Ohio, weighs 40.5 grams and a young
individual from Middle Paxton Twp., Pa., 39.3 grams, and a
subadult from Swan Creek Exp. Station, Allegan Co., Mich., weighs
49 grams.

_Color._--Winter pelage either all white, or brown as in summer;
upper parts about Raw Umber, or tone 2 of Carbo Brown of pl. 342
of Oberthür and Dauthenay. Underparts white at least on thoracic
region; approximately three-fourths of specimens with brown rictal
spot at angle of mouth or with this area covered by brown upper
parts which extend down on each side and meet on the underparts in
about one specimen out of three; upper lips and hind feet
ordinarily brown; toes of forefeet ordinarily white (see under
remarks for details of color pattern). Least width of color of
underparts in the specimens in which the dark color of the upper
parts does not encircle the body averages 60 per cent of greatest
width of color of upper parts, or including all specimens the
percentage is 42.

_Skull_ (based on specimens from Pa. listed in table of cranial
measurements, which see and plates 14 and 15).--Basilar length
29.7 and 28.6 in male and 28.0 in female; weights unavailable;
otherwise as described in _M. e. richardsonii_. The length of the
tympanic bullae seems to be actually less, and less in relation to
the basilar length, than in other American subspecies of _M.
rixosa_.

_Remarks._--Robert Kennicott's mention in 1859 (p. 245) of what seems to be this subspecies is the earliest reference to it that I can identify in the literature. He used the specific name _pusillus_ and it was not until 1900 that Samuel N. Rhoads proposed the name _Putorius allegheniensis_. Since 1900, several records of occurrence have been published which have made the geographic range of this race better known.

An adequate number of specimens has been gathered only from Ohio and from western Pennsylvania. Many from Ohio are without accurate external measurements taken in the flesh. The majority of the specimens from Pennsylvania owe their preservation to the willingness of local officials, who pay bounties on weasels, to save the skins of _Mustela rixosa_. These specimens ordinarily comprise the skin with locality but because the feet, external measurements in the flesh, and skulls are unavailable, the material is far from adequate and to give an accurate notion of the usual or average cranial characters of _allegheniensis_ in Pennsylvania, skulls from there are especially desirable.

A smaller percentage of the specimens from Ohio than from Pennsylvania have the brown color of the upper parts meeting on the underparts. Also, more of the specimens from Ohio are lighter colored and this suggests intergradation with the subspecies _campestris_ and _rixosa_ to the westward.

From Pennsylvania 23 animals in brown pelage are available. In 5 there is a rictal spot at the angle of the mouth; in 5 the area is white and in 13 the brown color of the upper parts is continuous over the area in question. Only 2 of 23 have the upper lips white. Eight have the color of the upper parts meeting on the venter thus restricting the white of the underparts to the chin, throat, and pectoral region, and 6 of these have a white area in the inguinal region as well. The toes of the forefeet are white in 3 of 4 animals suitable for examination in this regard and the hind feet are marked with white in 3 of the 8 animals which have the hind feet preserved. _Mustela rixosa_ in Pennsylvania parallels the species _Mustela frenata_ in that in this relatively humid area of the northeastern United States the color of the upper parts is darker and the area of the dark-colored upper parts is increased at the expense of the area of the light-colored underparts. Also _Mustela erminea_ in this same region (range of the subspecies _Mustela cicognanii_) shows the same tendency to darker color of upper parts and their extension in area at the expense of the area of the light-colored underparts, or was mentioned above.

It is difficult to account for the seeming absence of the species from New England and all that part of Canada and the United States south of the St. Lawrence River and northeastward from Pennsylvania. The size of females of _M. erminea cicognanii_ in that territory is so little more than in _rixosa_ that the latter possibly cannot successfully compete with the _erminea_ stock which may already occupy the ecologic niche to which _rixosa_ is adapted. It will be remembered that in western North America in territory seemingly climatically suitable for _rixosa_ it occurs no farther southward than the line below which _M. erminea_ has become reduced to a size comparable with that of _M. rixosa_.

Of 41 subadult and adult skulls assigned to this subspecies 24 have obvious lesions in the frontal sinuses evidently resulting from infestation by nematodes. More in detail, none of the specimens from Illinois (3 individuals), Pennsylvania (3 barely subadult), or West Virginia (2) displays lesions. From Wisconsin, Indiana, Virginia and North Carolina there is one specimen each and each specimen displays lesions. From Ohio, 17 of 23 specimens display lesions. From Michigan 3 of 8 specimens display lesions; 2 adults and one subadult have lesions and 5 subadults do not have lesions.

_Specimens examined._--Total number, 102 as follows: Arranged
alphabetically by states and within each state by counties from
north to south. Unless otherwise indicated, specimens are in the
United States National Museum.

=Indiana.= _Huntington County_: Roanoke, 1. _Wells County_:
Harrison Township, 1[76].

=Illinois.= _Lake County_: Deerfield, 3[60]; no locality more
definite than county, 1[60] _Cook County_: Northfield, 1[60]; La
Grange, 1[18].

=Michigan.= _Tuscola County_: 8 mi. N Caro, 1[76]. _Santilac
County_: Deckerville, 1[76]. _Allegan County_: Swan Creek Exp.
Station, 1[76]; Swan Creek Farm, 1[76]; T. 2N, R. 14W, 1[76];
Allegan, 1[76]. _Livingston County_: George Reserve, 1[76]; 1/2
mi. N Unadilla, 1. _Oakland County_: Rochester, 1[76]. _Macomb
County_: Romeo, 1[76]. _Washtenaw County_: 5 mi. SW Ann Arbor,
1[76]. _Branch County_: vic. Coldwater, 1[76].

=North Carolina.= "near Marshall," 1.

=Ohio.= Northern part of state, 1[81]. _Williams County_: Stryker,
1[60]. _Lucas County_: Monclova, 1[60]. _Erie County_: Sandusky,
2[76]; marsh near Sandusky, 1[76]; Berlin Heights, 1[76]; no
locality more definite than county, 1[2]. _Wood County_: 10 mi. NE
Bowling Green, 1[76]; Bowling Green, 4[76]; 3 mi. E Bowling Green
1[76]; Plain Township, 1[2]; Portage Township, 1[60]. _Loraine
County_: Wellington, 1[81]. _Huron County_: west of Monroeville,
1[76]. _Summit County_: Ira, 3[81]. _Portage County_: Suffield,
1[81]. _Hancock County_: Vanburen, 1[76]; Findlay, 1[81]; 9 mi. S
Findlay, 1[76]; no locality more definite than county, 7 (2[76],
2[81], 3[2]). _Mahoning County_: Ellsworth, 1. _Crawford County_:
"near Crestline," 1[81]. _Delaware County_: Sunbury, 1[2]; Lewis
Center, 1[81]; no locality more definite than county, 1[81].
_Licking County_: Johnstown, 1[2]. _Fairfield County_: Baltimore,
1[81]; Violet Township, 1[81]. _Meigs [= Gallia?] County_: Vinton,
1[81].

=Pennsylvania.= _Erie County_: McKeen Twp. 1. _Crawford County_:
Springboro, 1[1]; Pymatuning Swamp, between Hartstown and
Shermansville, Sadsbury Twp., 3[9]. _Mercer County_: Shenango
Twp., 1. _Lawrence County_: Little Beaver Twp., 1. _Butler
County_: Leasuresville, 1[9]; Clearfield Twp., 1; Valencia, 1[9].
_Armstrong County_: Ford City, Burrell Twp., 1. _Indiana County_:
Smicksburg, 1; N. Mahoning Twp., 2; White Twp., 1. _Allegheny
County_: South Hills, Pittsburgh, 1[9]; "near Pittsburgh," 1[9];
Fair Oaks, 1[9]. _Westmoreland County_: Bolivar, 1. _Dauphin
County_: Middle Paxton Twp., 1. _Washington County_: Finleyville,
1; Rea, 5; Beallsville, 1[1]; Claysville, 1. _Green County_: Deep
Valley, 1; Waynesburg, 1; Jefferson, 1; Cumberland Twp., 1.
_Fayette County_: Acme, 1[9]; _Somerset County_, 1. _Lancaster
County_, 1.

=West Virginia.= _Randolph County_: Huttonsville, 1.

=Wisconsin.= _Sauk County_: Sumpter Twp., 1[60]. _Dodge County_:
Beaver Dam, 1[50]. _Dane County_: Madison, 1; McFarland (=
MacFarland), 1.

=Mustela rixosa campestris= Jackson

Least Weasel

Plates 14 and 15

_Mustela campestris_ Jackson, Proc. Biol. Soc. Washington, 26:124,
May 21, 1913.

_Putorius pusillus_, Aughey, Sketches of the physical geography and
geology of Nebraska, p. 119, 1880, Omaha.

_Mustela rixosa campestris_, Swenk, Journ. Mamm., 7:329, Nov. 23,
1926.

_Type._--Female, adult, skin and skull; no. 171490, U. S. Nat.
Mus., Biol. Surv. Coll.; Beemer, Cuming County, Nebraska; April
18, 1911; obtained by G. Sharp; x catalogue no. 8440.

The skull is unbroken. On the left side, C1 and P2 are missing;
the other teeth are present and entire. The skin is excellently
made and in a good state of preservation.

_Range._--South Dakota, Nebraska and Iowa. See figure 28 on page
180.

_Characters for ready recognition._--Differs from _M. r. rixosa_
and _M. r. allegheniensis_ in larger size: Hind foot more than 25
in males and ordinarily more than 22 in females; in males total
length more than 216 and tail averaging more than 34; color
possibly slightly paler than in _M. r. rixosa_ and averaging paler
than in _M. r. allegheniensis_; from _M. frenata_ and _M. erminea_
of the same region by basilar length less than 32; tail less than
50, and lacking black pencil.

_Description._--_Size._--Male: Four adults from Nebraska yield
average and extreme measurements as follows: Total length, 231
(225-237); length of tail, 36 (32-39); length of hind foot, 29
(28-31).

Female: Six adults from Nebraska yield average and extreme
measurements as follows: Total length, 192 (184-225); length of
tail, 35 (28-40); length of hind foot, 23 (20.5-26).

_Color._--Winter pelage ordinarily white; as described in _M. r.
eskimo_ except possibly paler and certainly with line of
demarcation on side of head between upper parts and underparts
passing almost straight back without the dorsally directed
reëntrant angles of white behind the eye and ear; least width of
color of underparts in four specimens from Nebraska averaging 80
(49-89) per cent of greatest width of color of upper parts, but in
a fifth animal in summer pelage the brown color of the upper parts
encircles the body.

_Skull._--See measurements in table and plate 15; weight 1.1 grams
(male from Brown Co., S. D.); basilar length, 30.7 in male from
Clay Co., Neb., and 28.8 in female from same county; otherwise as
described in _M. e. richardsonii_.

_Remarks._--In his revisionary treatment of the American races of _Mustela rixosa_, Myron H. Swenk (1926:313) credits Samuel Aughey with recording this animal, _M. r. campestris_, from Nebraska, as early as 1880, under the name _Putorius pusillus_. In 1908, Swenk recorded the animal from the same state under the name _rixosus_ and in 1913 the race _campestris_ was formally named by H. H. T. Jackson.

On the testimony of a friend who had previously obtained several specimens for him, Swenk (1926:321) records the least weasel from Oshkosh, Garden County, Nebraska, which is a marginal record of occurrence to the southwest for _M. r. campestris_.

At an early stage in the study of American weasels the writer examined the specimens from Nebraska saved by Mr. Myron H. Swenk and recorded measurements of them. However, at the time of writing this account the specimens were not available for examination and the account of coloration is accordingly incomplete.

The large size, particularly the large external measurements, comprises the principal distinguishing character of this subspecies of the least weasel.

Of the four adults examined from Iowa and South Dakota one exhibits lesions such as result from infestation of the frontal sinuses by nematodes.

_Specimens examined._--Total number, 21 as follows. Arranged
alphabetically by states and by counties, from north to south in
each state. Unless otherwise indicated, specimens are in the
United States National Museum.

=Iowa.= _Howard County_: Chester, 1[12]. _Palo Alto County_:
Emmetsburg, 1[65]. _Kassuth County_; Algona, 1[65]. _Clayton
County_: National, 1. _Storey County_: Nevada, 1[65]. _Wapello
County_: Ottumwa, 1[65]. _Henry County_: Mount Pleasant, 1[66].

=Nebraska.= _Holt County_: Page, 1[35]. _Madison County_: Norfolk
1[35]. _Cuming County_: Beemer, 1. _Hamilton County_: Chapman,
1[35]. _Clay County_: Inland to 1 mi. east thereof, 7[35].

=South Dakota.= _Brown County_: shore of Sand Lake, S. 15 T. 126N,
R. 62W, 1. _Day County_: Waubay Migratory Waterfowl Refuge, 1.
_McCook County_: Salem, 1[102].

=MUSTELA FRENATA= Lichtenstein

Long-tailed Weasel

(Synonymy under subspecies)

_Type._--_Mustela frenata_ Lichtenstein, Darstellung neuer oder
wenig bekannter Säugethiere, pl. 42 and corresponding text
unpaged. 1832.

_Range._--From southern Canada southward over all of the United
States, México, Central America, Venezuela, and the republics of
western South America to southern Perú and extreme northern
Bolivia. All the life-zones from Alpine Arctic to Tropical are
inhabited. In the extremely desert region of southeastern
California and western Arizona the species is scarce or possibly
absent although recovery of a skull (see under account of _M. f.
neomexicana_) from near the center of this region at Potholes on
the Colorado River, and a reported occurrence in the mountains of
Baja California, México, indicate that a few individuals of the
species live in favorable habitat even in this desert region.

_Characters for ready recognition._--Differs from _Mustela erminea_, in regions where the two species occur together, by tail more than 44 per cent of length of head and body and by postglenoidal length of skull less than 46 per cent of condylobasal length in males and less than 48 per cent in females (see under characters of the species); from _Mustela rixosa_ by presence of black pencil on tail, caudal vertebrae more than a fourth (2/5-3/4) of length of head and body, basilar length of skull more than 34 mm.; from _Mustela africana_ by absence of thenar pad on forefoot, underparts without longitudinal, median, abdominal stripe of same color as upper parts, upper lips narrowly (rather than broadly) edged with color of underparts, longest facial vibrissae extending to or behind posterior margin of ear; presence of p2; more inflated (see pls. 23 and 30) tympanic bullae.

_Characters of the species._--Size large: Total length 300 to 550 mm.; tail two-fifths to seven-tenths of length of head and body, with distinct black pencil at end; caudal vertebrae 19 to 23; skull with long precranial portion; postglenoidal length, expressed as a percentage of the condylobasal length, less than 47 in females and ordinarily less than 46 in males; upper parts brown; light-colored underparts, in summer pelage, tinged with buffy or yellowish and continuous from chin to inguinal region; some subspecies (southwestern United States, México, Central America, and Florida) with white or yellowish facial markings which do not occur in any other American species of the genus _Mustela_.

_Geographic variation._--Forty-two subspecies are recognized, and the species is geographically more variable than any of the other 3 American species. Color, color-pattern especially on the head, relative proportions of the tail, hind feet, body including the head, and shape and size of the skull are the principal features in which geographic variation has been noted. The variation in the skull extends to the basicranial region (shape and size of tympanic bullae and related structures), interorbital region and preorbital region.

_Natural History._--Habitat and Numbers.--As has already been remarked, the long-tailed weasel is absent from the extreme desert of the southwestern United States and northwestern México. Possibly the absence of water to drink is the limiting factor. In southern Nevada the finding of weasels only in places that were well watered, even though small rodents suitable as food for weasels were even more abundant in the surrounding desert, supports this possibility that the absence of water to drink is the limiting factor. Also at Berkeley, California, in early December of 1927 in the canyon at the head of Dwight Way and in the autumn and winter of 1928 in Strawberry Canyon on the campus of the University of California, I trapped extensively for this species in different habitats and obtained, in all, four individuals no one of which was farther than 10 feet from water. The lesser cruising range of the individual weasel than of, say, the coyote, probably explains why, in an arid region, for example Pahranagat Valley, Nevada, only the meadow mice and their riparian associates are preyed upon by the long-tailed weasel whereas the coyote preys upon these riparian rodents and also upon the kangaroo rats and other rodents which are so abundant in adjoining habitats that are devoid of water.

In areas where water is available every few hundred yards, no particular habitat seems to be avoided in summer providing there is food for the long-tailed weasel. In winter (January and March) there obviously was a choice of habitat, possibly occasioned by more abundant food or more satisfactory shelter, or both, in Centre County, Pennsylvania, where Glover (1943B) found the population density in the chestnut-oak habitat to be one weasel per 6.5 acres in areas of tree cuttings and slash and one weasel per 13.3 acres in the open forest. In the scrub oak-pitch pine forest type the population was one weasel per 26.4 acres in tree cuttings and slash and one weasel per 38.2 acres in the open forest. No weasel was found in an area of 9.6 acres comprising a wood lot, the edge of the forest, abandoned fence rows and an abandoned orchard. The two types of forest in which he did find weasels, 25 in all, comprised 381.6 acres. Glover's (_op. cit._) data is the only precise information known to me on actual numbers of long-tailed weasels in a given area of any considerable size.

Fluctuations which I elsewhere (1946:57) have designated as multiannual fluctuations occur in this species but seemingly not in the degree that they do in _Mustela erminea_. This difference between the two species is to be expected because _M. frenata_ does not range so far northward toward the polar regions as does _M. erminea_ and populations of most kinds of animals in the polar, at least in the arctic, regions are subject to more extreme and more regular fluctuations than are kinds of animals in temperate or tropical regions. Indication of the means by which decrease in the weasel population is brought about is afforded by Osgood's (1935:156) observations around Rutland, Vermont. In the late winter of 1934, tracks indicated that weasels left their usual haunts and hunted cross lots, vainly trying to find food. Testing of the small mammal population in the spring and summer of 1934 showed that it was at low ebb. In the fall of 1934 mice and shrews were abundant again but weasels seemed to be entirely absent. The decrease in the population of weasels lagged behind the decrease in the population of the herbivorous prey as did the subsequent increase; this, of course, is the normal relation of carnivorous species of mammals and their prey, at least in and above the Transition Life-zone.

The average distance away from the central den which four weasels (sex unspecified) traveled in a single night at Ames, Iowa, was 312 feet; the maximum distance was 642 feet. These data were obtained in the winter of 1939 by Polderboer, Kuhn and Hendrickson (1941:115) who studied the tracks in the snow. In Manitoba, Criddle and Criddle (1925:143) noted that a female which lived in their basement often wandered more than half a mile away in search of food. In Michigan, Quick (1944:75) found the maximum distance traveled in one day (= night?) by a large male to be 3.43 miles although two miles was the average distance traveled by this individual. In 1942, from January 4 to March 4, in Centre County, Pennsylvania, Glover (1943B) studied tracks of 11 males and 10 females, in newly fallen snow, and ascertained that the distance traveled in a single night averaged 704 (60-2535) feet for the male and 346 (20-1420) feet for the female. The weasels in the open timber traveled farther per trip than those in the brushland and dense stands of trees.

Behavior

An adult female (now the holotype of _Mustela frenata nevadensis_) seen running across a field, and, I think, unaware of my presence, at every bound bent her back up so far that she reminded me of a measuring worm. For part of the time when running, the tail was held off the ground straight out behind, and then, for a while, inclined upward at an angle of about 45°. Another weasel that I saw in the daytime, and that I think was unaware of my presence, was bounding along among the _Baccharis_ bushes on the south-facing slope of Dwight Way Canyon, Berkeley, California. This individual, at each bound, arched the back up so high as to remind me, again, of a measuring worm.

The long-tailed weasel is a land mammal and unlike its close relative, the mink, is seldom seen in the water. That it can swim, however, is attested by the capture of one while it was swimming across the Río Ramos in México (Davis, 1944:381). Also, Green (1936), in May, in Gratiot County, Michigan, saw a weasel, running with a _Peromyscus_ in its mouth. The weasel dropped the mouse, entered the water and swam to a hole among stones.