136 Order RODENTIA 



activities of feeding, gathering grasses for its nest, enlarging its 

 burrow, cutting paths through the grass, or sunning itself. It is 

 always alert for a weasel, badger, dog, house cat, man, or hawk. 



The thirteen-lined ground squirrel feeds on seeds, on grasses 

 and other herbs, and on insects. At times during the summer, 

 nearly half its food may consist of grasshoppers, white grubs, 

 webworms, cutworms, and other insects. 



Young, numbering usually 7 to 10 per litter, are born in late 

 April or early May in a grass-lined nest below the surface of 

 the ground. By mid-June, the young have grown from nak 

 blind creatures to thin-bodied, big-headed, furred animals able 

 to clamber out of the burrow and nibble on herbs. By mid-July, 

 some young have dug simple burrows of their own. 



As summer progresses, this ground squirrel lays on quantities 

 of body fat, and by the time it enters hibernation its early sum- 

 mer weight has nearly doubled. In the fall when the days get 

 shorter and colder, this squirrel spends more time below ground 

 and becomes more and more sluggish. Usually by the time 

 grasses and seeds have been covered by snow, the ground squir- 

 rel has sealed the burrow entrance from within and has retired 

 to a hibernating cell, which is just large enough for the animal 

 and a little nest material. The cell is to one side of the burrow 

 proper and so situated as to remain dry. The animal rolls up 

 in a ball, with its nose tucked against its belly near its hind 

 legs, and goes into a deep sleep. The rates of breathing and 

 heart beat are greatly reduced, and the animals body tempera- 

 ture becomes nearly the same as that of its surroundings. When 

 the animal hibernates, it cannot effectively control or regulate 

 its temperature and therefore, if the temperature of the hiber- 

 nating chamber drops below the freezing point, the animal will 

 die. 



If the weather becomes unseasonably warm in winter, the 

 thirteen-lined ground squirrel may appear above ground for 

 short periods. Otherwise it remains below ground until March 

 or April. At this time it is thin, for its stored body fat has been 

 used during the long period of hibernation. 



Signs. — The print of each front foot shows only four toes; 

 the print of each hind foot shows five toes; that of the hind foot 

 measures about 1 \ j inches. A burrow entrance is usually 

 slightly less than 2 inches in diameter and without a pile of 

 dirt at the opening. 



