ANIMAL AGGREGATIONS AND SOCIAL LIFE 345 



and Toll (1923) tested the intelligence of hens and found that their 

 position in the social scale corresponds roughly with their IQ. 



During breeding time a hen is more easily irritated by other hens, 

 and frequently against her superiors. A hen with chicks is very 

 courageous; but if the chicks are removed, she may become timid 

 and retiring in her behavior. Cocks are said by Schjelderup-Ebbe 

 to behave in a manner similar to hens, but more ferociously. A cock 

 may interfere with the fighting of two hens, or even of two other 

 cocks, if he is superior to both. When among hens, he stands at the 

 top of the peck-order. 



This is not the picture of a simple society, though many of the 

 complexities of the organization have only been suggested in the 

 preceding summary. It may be objected that we have turned from 

 the formation of flocks in nature to the examination of the integra- 

 tion of artificial flocks of domestic fowls. It does not necessarily 

 follow that the details of flock organization are the same in nature, 

 but fortunately there is evidence bearing exactly on this point. The 

 same observer reports (1923) that in flocks of wild ducks essen- 

 tially similar group organizations exist. 



Another complex type of organization of a bird community in 

 nature has been worked out in detail, particularly by Allen (191 1, 

 1913) and by Howard (1920). This is the matter of territory in 

 bird life. The evidence shows clearly that the males pre-empt fairly 

 definite spaces before the breeding season begins, and maintain their 

 position during the breeding season, driving off intruding males be- 

 fore and after a female has appeared to accept the territory and the 

 male as her mate. Such spaced community organizations are ap- 

 parently widespread among birds and again indicate clearly a dis- 

 tinct social development. These territorial relations are not limited 

 to birds, but are also known for fishes (Reighard, 1920), as well as 

 for mammals. 



Among the fishes we have further evidence of the kind we have 

 been reviewing for birds. This is well known in the case of the 

 black catfish minnows observed by Bowen (1930). While it is true 

 that the group of young originates from the eggs guarded and ferti- 

 lized by a single male, yet, at least in the absence of the male, the 



