ANIMAL BEHAVIOR .,.,, 



on. The puppy, tussling with his fellow, pulling him about and 

 biting him, is preparing for real fighting with other dogs u hen he 

 -rows up. Thus play is a part of the schooling of the animal 

 for meeting the more strenuous requirements of adult existei 

 a schooling which is never necessarily completed, hence the play 

 instinct may even crop out in later life. It is then a potent fac- 

 tor in natural selection, for those individuals which have this 

 instinct most highly developed, are most likely to survive in the 

 struggle for existence under natural conditions ; under domesti- 

 cation the struggle loses much of its intensity just as in civilized 

 man, where it is largely replaced by rational choice. But among 

 wild animals we can readily see that the absence or subnormal 

 development of the play instinct would militate against the sur- 

 vival and propagation of the individual. 



The social behavior of animals merits likewise a brief notice. 

 It is a matter of common observation that many kinds of ani- 

 mals live in groups or herds or colonies, the various members 

 of which take a greater or less interest in their associates. 

 Among the lower animals such communities are most highly 

 differentiated among some of the insects, where, as in the case 

 of the bees, wasps, and ants, there is often a marked develop- 

 ment of a division of labor. Many fishes move in schools ; 

 many amphibians and many reptiles congregate together; birds 

 usually move in flocks ; herds of mammals are the rule. In 

 such associations the general welfare becomes to some extent 

 of common interest; in herds of buffaloes the old males will 

 collect in front of the females and the young and receive the 

 attack of the enemy. In troops of monkeys a cry of alarm 

 or of pain will bring companions from all sides. The funda- 

 mental factor in social behavior must undoubtedly lio in the 

 phenomena of reproduction and the consequent preservation oi 

 the best interests of the race. It is this which prompts the 

 stronger individuals to protect the weaker and the young, rather 

 than any impulse of magnanimous self-sacrifice. The most 

 highly differentiated feature of social organization, the monoga- 

 mous family, is found in a very few animals below man, and 

 such families appear to be merely the result of simple intelli- 

 gence resulting from the necessity for nest-building and caring 

 for the young during and after development. There is no satis- 



