RATS AND MICE FAMILY 



243 



TRUE LEMMING 

 Lemmus trimucronatus (Richardson) 



General Description. — A heavy-bodied, very short- 

 tailed Mou^e of tlie Arctic regions. Nose blunt and 

 hairy ; form stout, compact ; ears small, hidden in the 

 fur; tail short, stout, densely haired, tipped with long 

 hairs ; legs short ; fore feet large with long fossorial 

 claws, thumb rudimentary with long flat claw ; hind 

 feet short, broad, with hairy soles and naked tubercles ; 

 fur of medium length and somewhat coarse : general 

 color yellowish-brown. 



Dental Formula. — Incisors, — i • Canines, 5^" ; Pre- 



I - 1 0—0 



molars, ^^^ Molars, ^-^=16. 

 0—0' 3—3 



Pelage.— Adults : Se.xes identical. Seasonal varia- 

 tion occurring but not especially different in winter. 

 Head and fore part of back, mixed clove brown and 

 yellowish-brown ; below, bluish-gray mixed with yel- 



lowish-brown hairs; tail gray. Young: Similar to 

 adults but grayer. 



Measurements. — Total length, 5 inches ; tail ver- 

 tebrae, .7 inch ; hind foot, .9 inch. 



Range. — Arctic regions of North America. 



Food. — Green vegetation and roots. 



Related Species 



True Lemming. — Lcinmus trimucronatus (Richard- 

 son). Typical animal as described above. Arctic 

 America. 



Yellow Lemming. — I.cimnus hch'olus (Richardson). 

 Size large; coloration brownish-yellow or rust color, 

 mixed with black. Arctic .\merica. 



Black-footed Lemming. — Lcnimus nigripcs (True). 

 Fore feet black above; upper parts uniform cinnamon- 

 gray. Pribilof Islands, Alaska. 



Tlie Lemmings are a well differentiated group 

 of thick-bodied Mice quite closely related to the 

 common Meadow Mice of the temperate regions. 

 From the Meadow Mice they may easily be 

 told by their rather heavier bodies, very short 

 tail and large fore feet. None of the True Lem- 

 mings comes south of the Arctic regions. There 

 are but six species and subspecies. They do not 

 change color in the winter, as do the False 

 Lemmings. 



The True Lemming is an inhabitant of the 

 Hudson Bay region. It burrows extensively, and 

 its holes seem to be connected in an endless 

 labyrinth, mainly under the boulders between the 

 shore and some shallow lagoons. The number 

 •of young is from four to six. 



Another variety discovered by Richardson is 

 somewhat larger and more yellowish in color. 

 It has been described as a rusty black. Still 

 another, the Black-footed Lemming, is marked as 

 its name indicates by black on its fore feet. 

 This rodent lives in the Pribilof Islands, ofif the 

 coast of Alaska. They probably reached here 

 originally partly by swimming or on floating ice, 

 and this may have been the result of a migration 

 Ifor which sotne .Arctic Lemmings are famous. 

 A general movement of this nature is widespread 

 and is probably caused by overcrowding and con- 

 sequent scarcity of food. Dr. Coues says of 

 such a migration : " Nothing can stop them ; they 

 proceed straight on in their course, urged by 



some restless impulse, swimming broad rivers 

 and lakes and invading towns which may lie in 

 their wav." 



Photograph by H. T. Middleton 



DEER MICE 

 Climbing a telegraph pole 



