86 THE SENSES OF ANIMALS 



will have no success be he ever so careful about wind direc- 

 tion and scent. (See Plate 5.) 



I have been asked frequently which mammal has the most 

 sensitive ears and which one is the easiest to experiment 

 with. The first question is easily answered; the bats must 

 take pride of place on account of their "built-in" sonar 

 equipment about which Dr. Harrison Matthews will have 

 much to say in Part II. As far as ease of experiment is con- 

 cerned, I, personally, consider the galagos (bush-babies) offer 

 any student fine chances for testing their hearing. I have kept 

 many of these delightful creatures, and feel I must devote a 

 little space to them here. 



Bush-babies, which belong to the lemur family, are fairly 

 commonly kept as pets and they do not require any descrip- 

 tion. All species have large and very mobile external ears 

 which can be moved in many directions, giving a high 

 degree of powers of location. These powers are obviously of 

 value to the animal in detecting the presence and where- 

 abouts of enemies ; but it is not so generally known how 

 useful are these finely adapted ears in locating the flying 

 insects on which they feed to a considerable extent. 



I have carried out many experiments in this respect, but 

 before going further into them, I must hark back to sight 

 for a moment. Bush-babies are, in nature, exclusively crepus- 

 cular and nocturnal creatures, and they possess the huge 

 eyes which are associated with nocturnal vision. These eyes 

 are obviously used for catching food where conditions allow, 

 but as I have stressed before, no animal can see when it is 

 nearly or completely pitch dark. However, food must be 

 obtained even when conditions are most unfavourable for 

 hunting by sight. It is then that the large ears come into 

 their own. Moths and many other flying insects create sound 

 waves as they fly — anyone who has had a cockchafer in their 

 bedroom knows that — but it is one thing for us to be able 

 to hear the wing-flutter of such insects, and quite another 

 to catch one in the dark ; a bush-baby will make light of this 

 task. 



Let us suppose that we have a bush-baby in a roomy cage 

 placed in a room where the light can be conveniently 

 switched on and off. My own cages for bush-babies are 



