328 



THE MUSEUM. 



long as they are able to withstand a 

 low temperature, and food is access- 

 ible, they resist. Other causes than 

 cold may induce an animal to hiber- 

 nate, as when deprived of the supply 

 of food gathered during the preceeding 

 autumn. In such a case squirrels will 

 pass the winter in a state of torpor, 

 however mild the weather; while, with 

 an abundant food-supply, they will 

 simply sleep through the colder days 

 and awake to feast whenever the sun 

 shines brightly. 



Of the 30 or more animals found 

 here thirteen species are supposed to 

 be hibernating animals. These are 

 four species of bats, two of moles, 

 three squirrels, one ground squirrel, 

 one marmot, one jumping-mouse and 

 one Hcsperoviys. Of these probably 

 the bats are most sensitive to cold 

 and avoid exposure to it with the 

 greatest care; and yet I find that the 

 little red bat {Atalapha iwvcBboraccii- 

 sis) is very late in retiring for the sea- 

 son and appears with great regularity 

 early in February. Their actions at 

 this time indicate that considerable 

 food is to be had — flying insects are 

 abundant. While this bat's ordinary 

 habits do not differ from those of the 

 other species, it is apparently less sen- 

 sitive to low temperature and needs 

 but the least encouragement to arouse 

 from its hibernating sleep. It is also 

 less crepuscular in habit than the oth- 

 ers; but I do not know that this fact 

 has any bearing upon the irregularity 

 of its hibernation. 



Bats disappear in November or De- 

 cember, immediately after the forma- 

 tion of ice, but do not seem affected 

 by a mere succession of hard frosts. 

 As insect life is not materially affected 

 by the first few frosts, there does not 



seem any reason for their withdrawal 

 from active life and therefore it is not 

 surprising that even up to Christmas 

 bats should be seen flying at sunset in 

 considerable numbers. When the 

 steady cold of an average winter fairly 

 reaches us bats hibernate in two ways. 

 If they resort to the ordinary shelter 

 of a hollow tree or similar locality 

 that is considerably exposed to the 

 wind then many individuals cluster to- 

 gether; and contact is mutually bene- 

 ficial, for the torpor of hibernation is 

 not rapidly but rather gradually ac- 

 quired. Such clusters of bats, if dis- 

 turbed immediately after gathering to- 

 gether, are as resentful as when cap- 

 tured during mid-summer; and not un- 

 til three or four days have elapsed do 

 they become insensible to disturbance. 

 If this be very violent and the creat- 

 ures roused suddenly a curious con- 

 dition of aimless activity ensues but 

 lasts for a short time only and often 

 ends in death. 



On the other hand I have very fre- 

 quently found solitary bats in curious- 

 ly out-of-the-way places, where they 

 were so protected that they could not 

 have suffered from the severity of the 

 season, however intense. In such 

 cases the torpor was never profound, 

 the temperature of the body but little 

 reduced and the heart's action almost 

 normal. For instance: a single dusky 

 bat ( ]^cspertilio fuscits) slept, or hi- 

 bernated, as described, for thirteen 

 weeks, in the attic of my house. It 

 clung to a nail driven in the wall of 

 the chimney, and was protected by a 

 piece of woolen cloth hanging from a 

 beam above it. The chimney retained 

 a little of the warmth derived from the 

 smoke-flues which passed through it 

 and which were in constant use dur- 



