oct 15, 1925 The Hibernation of Ground Squirrels 769 
the first few days of aestivation, as is shown by a Townsend squirrel 
in Figure 6. Their eyes were sunken very deeply into the orbits, 
and their lips became very shapeless and deathlike. Occasionally, 
Fig. 5.—Same squirrel as shown in Figure 4, After going into hibernation on the sixteenth day of 
fasting, he slept for about six days, when he awoke and was given food. Later he was branded 
and turned in one of the larger outer yards where he ran all summer, regaining his normal weight 
Fig. 6. —Observations in the yards have given interesting testimony on the manner in which 
aestivation comes over the squirrels. During the few days previous to going into the comatose 
condition, they gradually cease eating. Then, as in the case of the Townsend squirrel shown 
here, they go into torpor. They do not always curl up tightly at first, and they may waken after 
a day or so. At this time they get back their normal temperature, which they may retain for a 
short time before going back to sleep. Later in the winter, however, they appear extremely 
torpid, and at times it is difficult to believe they are really alive, as shown in Figure 2 
after long watching, one would see a movement pass across the flank, 
resembling in slowness that of the peristalsis movement shown by a 
recently chloroformed mammal in the laboratory. From this condi¬ 
tion they might transform in a few hours to the state of very live and 
warm squirrels. 
