THE CANADIAN FIELD-NATURALIST 



VOL. XXXIII. 



SEPTEMBER. 1919. 



No. 3. 



NOTES ON CANADIAN WEASELS. 



By J. Dewey Soper. 



The Least Weasel, Musiela rixosa (Bangs). 



This diminutive carnivore is doubtless the least 

 known of the North American weasels. About 

 fifteen records all told, mostly from Canada, in- 

 dicate both our limited knowledge and the scant 

 possession of scientific material relative to the species. 

 Since 1857 when Baird first described the species, 

 data concerning its life history has accumulated 

 slowly and even yet is of very limited extent. 



The range of rixosa, according to Seton' extends 

 in a broad band, roughly, eight or nine hundred miles 

 in width diagonally across the continent from Mon- 

 treal and the south-western extremity of Lake 

 Superior to Alaska. As a boreal species it is re- 

 stricted to the Arctic, Hudsonian, and Canadian 

 life zones. In north-western Alaska a race of this 

 species P. esJ^imo (Stone) is recognized, also what 

 may prove to be a race is Rhoads'- allegheniensis 

 from Pennsylvania. Thus, theoretically, southern 

 Ontario comes within the range of the Least Weasel, 

 but I know of no records from the region. 



The Least Weasel is not only the smallest of the 

 weasels, but is the smallest known beast of prey in 

 the world. 



In summer, the upper parts including the tail are 

 of an even light brown color, the under parts being 

 pure white. The winter coat is entirely white. TTie 

 tail is very short and lacks at all seasons the black 

 tip. 



As a carnivorus animal its diminutive proportions 

 may be better appreciated when compared with a 

 mouse for instance. The Least Weasel habitually 

 preys on mice, but exceeds them but little in size. 

 A glance at the following measurements of rixosa 

 will reveal slight difference in this respect from the 

 genus Microtus, the meadow mice, etc. 



Total length about 6J/2 inches (166 mm.); tail 

 vertebrae, 1 !/4 inches (32 mm.); hind foot, 13-16 

 inches (21 mm.) 



Measurements of a large meadow mouse (M. 

 penns^lvanicus) taken Feb. 17, 1918, coll. No. 243, 



iSeton, E. 'P., JAfv Hisl. of Nortlicrn Animals. 

 Vol. II, p. 861, lliO'.i. 



2Rhoads, S. N., Mainni. of Pcnii. and X.J., pp. 

 173-176, 1903. 



male: Length, 168 mm.; tail, 50 mm.; foot 21 mm. 



It will be noticed that the latter is the largest, 

 but this one was of more than ordinary size. 



The only place I ever came into contact with 

 the Least Weasel is Edmonton, Alta., and even there 

 where weasels are common only one was taken 

 within a certain period of time, during which about 

 one hundred and fifty of the other species were 

 captured. This fact indicates its rarity in that 

 region. 



I found it about Nov. 13 in one of my traps, along 

 the White-mud river, a few miles south-west of the 

 city. It was pure white, proving it takes on its 

 winter pelage as soon as the other species. 



The locality in which it was collected was that 

 ordinarily frequented by M. cicognanii and M. 

 longicauda — meadow-like river-tracts sparsely over- 

 grown with poplar. The first sight of its body made 

 me think of an Albina meadow mouse. Even such 

 small mammals sometimes spring the larger traps as 

 all trappers know. To those who are unfamiliar 

 with the many disappointments of the trap line, it 

 may be said that after repeated failures at certain 

 "sets" when bait disappears and traps are myster- 

 iously sprung, a crushed shrew or deer-mouse in the 

 jaws will at last dispel the mystery. 

 The Long-tailed Weasel, Musiela longicauda 

 (Bonaparte). 



This species, the largest of our Canadian weasels, 

 should not be confused with others of the family. 

 Great strength for its size is suggested in the mus- 

 cular contour of its make-up. The legs are com- 

 paratively short and stout, the body compact and 

 very muscular, and the head massively formed in 

 alliance with its other physical proportions. 



In size it approaches that of a small mink and in 

 summer coat with hasty glance might be mistaken 

 for one. In winter, as Seton remarks, it could 

 easily be mistaken for a big white squirrel, that is, 

 upon the ground. It has a closest resemblance to 

 M. novcboraccnsis but as the range of the two 

 species do not coincide and as extra limital occur- 

 rences are rare, little or no confusion should be ex- 

 perienced in the field. 



