ADAPTATIONS TO HIGH ALTITUDES 47 



to life at great heights. The Common Dormouse 

 (Muscardinus avellanarius) is a very characteristic 

 alpine animal, able to live at an altitude of 5,000 feet ; 

 one of its adaptations is that it is a winter-sleeper. The 

 Chamois of Switzerland, a goat-like antelope of Asiatic 

 origin, is a hardy and adventurous climber, and the 

 close hair of its coat is adaptively protective against 

 the cold. 



One of the grandest walks in Scotland, and that is 

 saying much, is from the valley of the Dee to the valley 

 of the Spey across the Larig Pass in other words, 

 from Braemar to Aviemore. If we climb a little near 

 the watershed we are sure to come across a very char- 

 acteristic bird of the mountains the Ptarmigan 

 (Lagopus mutus\ first cousin of the Willow Grouse 

 and second cousin of the Red Grouse. Two of its 

 adaptations to high altitudes are striking. It is pecu- 

 liar among birds in moulting three times in the year, 

 having a somewhat grouse-like spring dress, a greyish 

 summer dress, and a white winter dress. The winter 

 plumage is snowy white except for a few black feathers 

 in the tail and a black bar in front of the eye, and this 

 whiteness gives the bird a garment of invisibility 

 among the snow. Sometimes among the snow one 

 almost puts one's foot on a crouching Ptarmigan. 

 Moreover, for a creature with a high body temperature 

 living in very cold surroundings there is no more 

 economical dress for preserving the animal heat than 

 a suit of white feathers or white fur. The same fitness 

 or adaptation is seen in the Mountain Hare which 

 turns from yellowish grey to white all but the tips of 

 its ears and in the reddish-brown Stoat which turns 

 into the Ermine, all white save the tip of its tail. We 



