CLIFF-DWELLERS 29 



"In cold climates, where bats have to club to- 

 gether for mutual warmth, fifty or sixty of them 

 have been found in one bundle, representing an 

 aggregate weight of about fifteen pounds, all sup- 

 ported by one thumbnail! The head-centre, or the 

 one that supports the weight of the group, must 

 sleep as warm as a child in a feather-bed; but it is 

 hard to understand how the outsiders can survive 

 the cold season, for, in spite of their voracity, bats 

 accumulate no fat, and the flying membrane is a 

 poor protection against a North American winter. 

 The only explanation is that their winter torpor is a 

 trance, a protracted catalepsy, rather than a sleep ; 

 hibernating bears and dormice get wide awake at 

 a minute's notice, but I have handled bats that 

 might have been skinned without betraying a sign 

 of life, and needed more than the warmth of my 

 hands to revive them, for their wings were quite 

 brittle with rigid frost. Bats prefer a cave with 

 tortuous ramifications that shelter them against 

 draughts, but still with a wide though not too visi- 

 ble opening, as they do not like to squeeze them- 

 selves through narrow clefts. A dormitory com- 

 bining these requisites is sure to attract lodgers 

 from far and near. , . . The Mammoth Cave, with 

 its countless grottoes, has only two bat-holes, whose 



