43cS 



EVOLUTION AND ANIMAL LIFE 



Environmental instincts concern the creature's mode of life. 

 Such are the burrowing instincts of certain rodents, the wood- 

 chucks, gophers, and the like. To enumerate the chief phases 

 of such instincts would be difficult, for as all the animals are 

 related to their environment, this relation must show itself in 

 characteristic instincts. 



The instincts of courtship relate chiefly to the male, the female 

 being more or less passive. Among the birds the male in spring 



is in very many species 

 provided with an 

 ornamental plumage 

 which he sheds w r hen 

 the breeding season 

 is over. The scarlet, 

 crimson, orange, blue, 

 black, and lustrous 

 colors of birds are 

 commonly seen only 

 on the males in the 

 breeding season, the 

 young males and 

 the old males in the 

 fall having the plain 

 brown gray or streaky 

 colors of the female. 

 Among the singing 

 birds it is chiefly the 

 male that sings, and 

 his voice and the in- 

 stinct to use it are 

 commonly lost in 



great degree when the young are hatched in the nest. Among 

 certain fishes the males are especially brilliantly colored in the 

 breeding time, but there is little evidence of any personal at- 

 tempts to display these colors before the females. 



Among polygamous mammals the male is usually much 

 larger than the female, and his courtship is often a struggle 

 with other males for the possession of the female. Among 

 the deer the male, armed with great horns, fight to the death 

 for the possession of the female or for the mastery of the herd. 

 The fur seal has on an average a family of about thirty-two 



FIG. 272. Horns of two male deer interlocked while 

 fighting. (Permission of G. O. Shields, publisher 

 of "Recreation.") 



