Oct. 15, 1925 
The Hibernation of Ground Squirrels 
765 
After awakening from hibernation the squirrels began to take on 
weight, as is shown by the record of female 8. On March 9, three 
days before the hibernation ended, she weighed 370 grams, on May 
16, she weighed 411 grams, having gained 40 grams in 64 days or 
0.62 gram per day, a little more thanlialf the daily loss in the winter. 
There was a greater gain shown by female 4. On coming from 
hibernation, probably March 14, she weighed 301 grams on March 
19; on May 16 she weighed 422 grams, having gained 121 grams in 
58 days, or a little more than 2 grams per day. Of course, the 
weight on May 16 might have been increased by bulky food. Im¬ 
mature male 6 increased 55 grams in weight between March 30 and 
May 24; immature female 10 increased 86 grams between April 4 
and May 12; immature male 11 increased 28 grams between March 
30 and May 24. 
Fio. 2.—A Townsend ground squirrel In hibernation. This squirrel, brought from low elevation 
of 1,471 feet, went into aestivation at the remarkably early date of June 14. After an almost 
continuous sleep of eight months, he appeared as in Figure 3 
DURATION OF HIBERNATION IN THE HIBERNATION CABIN 
A very remarkable hibernation record was that' of the CiteUus 
townsendi male 5. For a few days prior to June 14, 1912, he had 
not been eating regularly and had been plugging up the cracks in 
the nest box and the hole in the chute leading to the yard. On 
June 14 he was found in aestivation (fig. 2). He passed through 
the usual hibernation. On January 31, 1913, he showed signs of 
having been awake, as he had tom down part of the plug m the 
exit shaft, which had been untouched since being put in by him in 
June. He was still in hibernation February 13, having been in a 
state of aestivation and hibernation for a period of 244 days or, 
roughly speaking, 8 months. It is possible he would have ended his 
hibernation in January had he been at liberty, but finding the exit 
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