198 GNAWING ANIMALS 



descends quite steeply into the earth until it passes below the 

 frost-line (two to three feet), after which it runs off in a more 

 or less horizontal course for ten or fifteen feet farther. If 

 the burrow is an old one and much used, it is a long and 

 difficult task to dig to the end of it, and few boys undertake 

 it more than once. 



As in the case of nearly all burrowing rodents of cold 

 latitudes, nature has so adjusted the life of this animal that 

 it survives the long and dreary winter in the strange, half- 

 dead condition called hibernation. To make this possible, 

 the young are born early in the year and mature early, and 

 during summer and autumn take on a great quantity of fat. 

 At the approach of winter, it curls up in its burrow for a sleep 

 of from three to four months' duration. 



By the investigations of Dr. P. R. Hoy, it has been dis- 

 covered that in the case of the Thirteen-Lined Spermophile, 

 the action of the heart is reduced from two hundred to only 

 four feeble beats per minute, the temperature is reduced 

 from 105° to 58°, and there is no visible breathing. The cir- 

 culation of the blood was so feeble that when a limb was 

 amputated, only a few drops of blood slowly oozed from the 

 wound, while the nerves showed no sensitiveness. In fact, 

 the animal was in a condition of suspended animation, as 

 if under the influence of chloroform. In the northern por- 

 tions of its range, this spermophile hibernates from about 

 November 20 to April 1. 



Franklin's Spermophile 1 looks very much like a slender- 

 bodied, short-tailed tree squirrel; and very often it is called 



1 Ci-tel'lus frank'lin-i. 



