WHY DO ANIMALS BECOME EXTINCT? 235 



example of the dependence of plants on ani- 

 mals, for their existence hangs on that of a 

 small moth whose peculiar structure and hab- 

 its bring about the fertilization of the flower. 

 The two probably developed side by side until 

 their present state of inter-dependence was 

 reached, when the extinction of the one would 

 probably bring about that of the other. 



It is this inter-dependence of living things 

 that makes the outcome of any direct inter- 

 ference with the natural order of things more 

 or less problematical, and sometimes brings 

 about results quite different from what were 

 expected or intended. 



The gamekeepers on the grouse moors of 

 Scotland systematically killed off all birds of 

 prey because they caught some of the grouse, 

 but this is believed to have caused far more 

 harm than good through permitting weak and 

 sickly birds, that would otherwise have fallen 

 a prey to hawks, to live and disseminate the 

 grouse distemper. 



The destruction of sheep by coyotes led the 

 State of California to place a bounty on the 

 heads of these animals, with the result that in 



