MOUNTAIN FAUNAS 87 



and as these are typical denizens of cold steppes, it is 

 natural that they should occur also in the steppe region 

 of lofty mountain chains. In Europe the Alpine marmot 

 is found in the Alps, the Pyrenees, and the Caucasus, 

 though it once occurred on the low groimd also. In 

 Central Asia many kinds of marmots occur, though 

 none extend to the south of the Himalayas. The 

 Himalayan marmot, allied to the bobac of the steppes, 

 is limited to the region above the tree limit, that is, to 

 the barren wastes which most nearly resemble the home 

 of the bobac, the usual elevation being 12,000 to 13,000 

 feet. In North America we have similarly a Rocky 

 Mountain marmot, resembling in habits the Alpine form. 



The voles (Arvicola) are well represented in mountain 

 regions, the genus showing a remarkable tendency to 

 run into varieties, or species, in particular localities. 

 Thus in the Alps and Pyrenees there occurs the very 

 curious Alpine or snow vole {A. nivalis), which is some- 

 times pure white, but is structurally very near the 

 continental field vole and the bank vole. It differs 

 notably from these forms in its habits, for it lives high 

 up the mountains, even above the snow-line. It has 

 been found on the Finsteraarhom at a height of 12,000 

 feet, but on account of its habits is rarely seen. It 

 appears to live actually beneath the snow, making 

 runs beneath it after the fashion of the Arctic lemming, 

 in its search for vegetation. Other mountain species 

 occur in the Himalayas and Tibet. 



South America, with its paucity of ungulates, has 

 a considerable number of peculiar mountain rodents. 

 Thus the common chinchilla {Chinchilla lanigera), with 

 its soft thick fur, inhabits the higher parts of the Andes, 

 living in rocky ground, and displaying marvellous 

 agility. A larger form {Lagidium cuvieri) inhabits the 



