FIELD BOOK OF MAMMALS 



incisors. External characters unknown. . . . Confined, so 

 far as known, to the island of Unalaska, Alaska Peninsula." 

 (G. M. Allen) 



St. Lawrence Island Lemming. — Dicrostonyx exsul G. M. 

 Allen _ 

 Resembling ruhricatus but grayer in color. Upperparts 

 (summer) pinkish gray ; gray on nose and cheeks ; sprinkling 

 of black hairs on nose, on cheeks, and along median line of 

 back; ochraceous buff mixed with tawny about ear; sides 

 brighter than back; feet pale buff; tail whitish; underparts 

 washed with ochraceous buff, chin and undersides of fore- 

 legs pure white, throat tinged with tawny. Winter pelage 

 white. Total length, 5.8 inches; tail vertebrae, .68 inch; 

 hind foot, .80 inch. Found only on St. Lawrence Island, 

 Bering Sea, Alaska. 



Greenland Collared Lemming. — Dicrostonyx grcenlandicus 

 (Traill). 

 Most like ruhricatus but much smaller and differing in 

 various cranial characters. Upperparts (summer) grizzled 

 blackish and gray ; neck and shoulders washed with ochrace- 

 ous orange ; narrow black median stripe from nose to shoul- 

 ders; feet and tail white tinged with buffy; underparts 

 washed with ochraceous orange. Winter pelage white. 

 Total length, 4.3 inches; tail vertebras, .35 inch; hind foot, 

 .60 inch. Found "from about latitude 69° N. on the east 

 coast of Greenland, northward to the limit of land, 83° 24', 

 and thence westward along the coast of North Greenland 

 to the Kane Basin, and across the Robeson Channel to 

 Grinnell Land, Ellesmere Land, and south to Baffin Land." 

 (G. M. Allen) 



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The Collared Lemmings are the only Mice which change 

 color from summer to winter pelage. In summer they look 

 like short-tailed Meadow Mice, brownish or grayish in color, 

 but when winter comes a pure white pelage appears and with 

 it the greatly enlarged claws on the front feet. By the single 

 character of the specialized claws, winter specimens of the 

 genus Dicrostonyx may be easily distinguished. 



This genus is -Arctic and Subarctic in its distribution and is 

 usually found on the barren, open areas. These Mice make 

 burrows and have underground nest chambers which are 

 lined with grass and moss. In winter they make many run- 

 ways under the surface of the snow, but in summer there are 

 very few surface runways such as are made by Meadow Mice. 

 Collared Lemmings are chiefly nocturnal in habit. 



These Mice sometimes become so abundant that they are 

 observed in a great migration similar to that of the Lemmings 



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