160 NORTH AMERICAN FAUNA [No. 55 



are sometimes called " rock chucks", because they live usually among 

 the rocks, but the Old World name of marmot seems best suited to 

 them. Being heavy, slow, and to their numerous enemies defenseless 

 and very toothsome animals, they must of necessity have secure pro- 

 tection, which is found among the rocks. Clefts and caves in ledges 

 and cliffs or the deep interminable interstices of great talus slopes 

 are their favorite haunts, and the seemingly erratic distribution of 

 the species is due to the irregular uplifting and outcropping of rocks. 

 A sloping mass of huge broken and angular blocks at the base of 

 a lofty cliff is a favorite home for a family, or several families, some- 

 times. Such homes appear almost as a friendly colony. Some perch 

 or lie flattened on high points to watch for enemies, while others 

 wander out only a short distance from cover to feed on the short 

 grass, native clovers, and other green vegetation. A short, sharp 

 whistle, or metallic chirp, from a sentinel sends all rushing for the 

 rocks with rolling gallop and flapping tails. They dive into the 

 dark caverns or pause at the doorways to see if the danger is real 

 or imaginary. Sometimes a chorus of short sharp whistles sounds 

 from all parts of the rock slide but usually only the one or several 

 sentinels keep up the calls until the danger is passed or all have 

 taken refuge deep under the impenetrable mass of rocks. 



So impregnable are their strongholds that little is known of their 

 home habits, where or how their nests are placed, the appearance of 

 the very young, or where they sleep through the long winter. It 

 is probable that in many places burrows are dug under the rock piles, 

 as occasionally they are at the edges or under some big boulder; 

 but frequently the animals live in cracks and small caverns that go 

 back into solid cliffs and walls where extension of the cavities would 

 in many cases not be possible. 



Hibernation. The marmot provides no food stores for winter 

 except the dense layer of fat inside of the skin, another layer over 

 the outside of the muscular walls of the body, and as much stored 

 inside as the body cavities can well accommodate. The full accumula- 

 tion of fat must double the weight of the animal, but unfortunately 

 actual weights are not available for comparison. Usually in August 

 or September, with the coming of frosty nights, all disappear in their 

 nests and sleep securely until the warm days of February or March, 

 the time of entering and emerging from hibernation varying con- 

 siderably with the weather, age, and food supply. 



Breeding habits. The females have 5 pairs of mammae 1 ingui- 

 nal, 2 abdominal, and 2 pectoral as in most of the ground squirrels. 

 The number of young is probably as in other subspecies of the group, 

 usually 4 to 6 but sometimes as high as 8. Half-grown young in 

 June would indicate May as the time of birth and March as the 

 mating season. Late in August the young are not full grown but 

 large enough to take care of themselves and, except for late litters, 

 are usually fat and ready to hibernate. 



Food habits. The principal native food of these marmots is green 

 vegetation, short, tender nutritious grasses, little native clovers, 

 stonecrops, and a great variety of tender plants. Later in summer 

 it consists more of flowers and green or ripening seeds, always the 

 richest food they can find. The stomachs are large and usually 



