32 ANIMAL LIFE OF THE BRITISH ISLES. 



becomes a conspicuous feature, and its variation affords one of 

 the characters for identification of the species. Our two Horse- 

 shoe Bats alone are without any prominent tragus. 



It is considered that the Bat's powers of flight are superior 

 even to those of the birds. This is especially evident if we watch 

 the rapidity with which it can change its speed, suddenly stop- 

 ping when in full flight, then making sudden swoops and turning 

 somersaults in a way that would evoke the admiration of the 

 stunt-loving airman. The females as a rule have larger wings 

 and heavier bodies than the males. 



Perhaps to the majority of people the Bat appears to be a 

 creature without a voice. It does, however, utter a shrill squeak 

 which is so highly pitched that many human ears are incapable 

 of perceiving it. On the other hand, the Bat has similar 

 deficiencies ; and it has been proved that low notes, however 

 loud; make no x impression on the Bat, though a sharp clicking 

 sound or the tearing of paper will alarm him at once. 



Our Bats are all nocturnal in their habits, though a few 

 indulge in occasional flights by day. Most of them have definite 

 hours for flight, the time depending upon the flight period of the 

 insects they prey upon particularly. They retire for the day into 

 dark situations, such as hollow trees, caves, outhouses, or under 

 roofs. In these sleeping places great numbers often congregate, 

 and several species may be represented. During bad weather 

 when, of course, their insect prey also remains under cover 

 they do not leave their daytime shelter. When asleep their 

 body temperature falls considerably. In harmony with this 

 nocturnal habit we find that our Bats are usually dull coloured 

 some tint of brown with the underside lighter than the upper. 



All the British species hibernate, and before the beginning of 

 this period they develop a good deal of fat to carry them through 

 it. On any day in the winter when there is any considerable 

 rise of temperature they wake at once and look around for 

 insects that have been aroused by the same means. The larger 



