HIBERNATION 153 



The food of this ground-squirrel consists of a few grasshoppers, 

 crickets and beetles, some grass blades and other tender leaves and 

 growing tips, a few roots and a very large proportion of grains and 

 other hard seeds. Soft fruits, apples and berries are not despised, but 

 seeds must be regarded as the staple diet of the animal. 



The home is an underground chamber, reached by a hole going 

 down almost vertically for about a foot and then turning horizontally 

 and ramifying into two or more passages. Generally there are two or 

 more vertical passages connecting the burrows with the outer world. 

 The young are born in these subterranean homes some time during the 

 early summer. The family breaks up in the late summer and appar- 

 ently the young make new burrows for themselves and the animals 

 hibernate singly, but 'of this I am not sure. 



Hibernation begins at the onset of cold weather. The exact date of 

 their final retirement to winter quarters varies with the season, the lo- 

 cality and the individual, and yet there is a certain amount of uniform- 

 ity about it. Thus in 1909 in southern South Dakota there was no 

 frost until October 9 or 10, when the temperature suddenly dropped 

 and on October 11 it was several degrees below freezing point with a 

 bitter northerly wind that made it seem much colder. Until this 

 "cold snap" I had seen ground-squirrels daily. Afterward, there was 

 a period of three or four weeks of very balmy weather, but I did not see 

 another ground-squirrel although I had excellent opportunities had 

 they been active. 



The end of their hibernating period varies somewhat and it probably 

 depends somewhat upon the temperature. On the banks of the Mis- 

 souri Eiver, in South Dakota, the first of these little animals are usually 

 seen whisking about their burrows some time late in March. Usually a 

 number are to be seen on the same day that the first one appears. In 

 this they show a striking similarity to the woodchuck as they also do in 

 their habit of staying out in all kinds of weather, once they have made 

 the venture. Thus in the spring of 1910 in mid-April we had a snow- 

 storm lasting two days and piling the snow up three feet deep in places. 

 The very day that the storm subsided I saw ground-squirrels running 

 cheerfully about, buried to their hips in snow. 



A captive animal of this species afforded opportunity for a very in- 

 teresting winter study. He was captured in an insect net in September 

 and placed in a wooden box which had a front of fine wire mesh. He 

 was fed corn, small grains, potato, apple and sweet potato. Water was 

 given him also but he did not seem to use any of it and I finally ceased 

 to give it. The small grains were the favorite food and he would not 

 eat the outer part of the corn grain unless driven by actual hunger 

 although the heart (embryo) of the grain was gnawed out. The cage 

 was kept in the supply closet of my laboratory. The former was without 



VOL. LXXXIV. — 11. 



