Oct. 15,1925 
The Hibernation of Ground Squirrels 
767 
temperature 4° to 6° F. below freezing about its nest. On Feb¬ 
ruary 3, 1914, the box temperature where the squirrels were kept was 
30.5° F., resulting in no harm to the hibernating squirrels. From 
this one can understand why it is that young squirrels risk the 
danger from frost when hibernating only 6 or 7 inches below the 
surface of the ground. 4 It was noted also in the hibemarium that 
the squirrels would come out of the hibernation condition if the 
boxes containing them went much below the freezing point. Of 
course, the nest material would assist in keeping the temperature 
up (fig. 1). 
BODY TEMPERATURE OP HIBERNATING SQUIRRELS 
The body temperature of squirrels in hibernation was taken. 
At first this was reached approximately by placing the thermometer 
against the ventral side of the squirrel. Later, rectal temperatures 
were taken. The results ara given in Table II. From this table it 
is seen that the average body temperature of three hibernating 
squirrels tested by the rectal method is 42.3° F., or about 56° below 
normal. It is noteworthy that in the case of the squirrel tested 
February 12 her temperature rose from 38° F. to normal 98° in 
four hours. 
Table II. — Body temperatures of hibernating sguirrels y in degrees Fahrenheit 
* Date 
Kind of test 
Temper¬ 
ature of 
nest box 
Temper¬ 
ature of 
squirrel 
Dura- 
tionof 
test 
Jan. 20,1912... 
Contact.___ 
38.5 
41.0 
Mar. 1,' 1912_ __ 
.do__ 
34.0 
38.1 
Feb. 3,1914...... 
Rectal__ 
30.5 
49.0 
18 
Peb. 12,1914____ 
.do__ .. 
36.0 
38.0 
6 
Feb. 16,1914 _____ 
.....do. 
40.0 
15 
RELATION OP FEEDING TO AESTIVATION AND HIBERNATION 
It was noticeable that squirrels preparing for aestivation or coming 
from hibernation used very little food, and this was taken at intervals 
of some days. For example, in August a Columbian ground squirrel 
was observed to have an interval of seven days between times of 
eating. On August 25 it partook of a very little food. This seemed 
to be its last meal before going into hibernation. A Townsend squirrel 
did not eat much for several days before going into aestivation. 
That they need not eat during hibernation is shown by a Colum¬ 
bian under observation. It was given no food from November 1, 
1911, to March 13, 1912. When they were given food while awake 
it seemed to interfere with the regularity of their hibernation and 
even to keep them out of this condition altogether. In the case of 
Columbian female 7, taken from the hibernation condition on No¬ 
vember 11, 1911, she afterwards awoke and was fed November 14. 
She remained awake for some days, but went into hibernation No¬ 
vember 20. She ate again December 14, and was in hibernation 
again on December 16. She ate once more January 1, 1912, and 
went into hibernation January 2. Again on January 17 she ate and 
went back into hibernation the following day. On January 29 she 
awoke and ate and did not go back into hibernation. 
* Shaw, W. T. the hibernation of the Columbian ground squirrel. Canad. Field-Nat. 39 
