348 



POPULATION ECOLOGY: 



because true behavior is restricted to animals with 

 complex nervous systems. Animal behavior definitely 

 can influence the ultimate distribution pattern of 

 offspring. In many nonsocial animals the young are 

 forced to leave the parental environment (emigrate) 

 by the parents. For this reason, the distribution of 

 animal offspring is molded by behavior patterns. 



SOCIAL BEHAVIOR 



One can now appreciate that the presence of a 

 species in a given habitat is allied to social behavior, 

 and true social behavior is limited to animals. If the 

 relations of individuals within the same species are 

 close, or social, the spatial unit is clumped. If 

 individual associations within species are remote or 

 antagonistic, that is, nonsocial, local occurrence is 

 random or even spaced. Note that we are not using 

 "social" in the restricted sense of social insects. 



Certain terms are useful in reference to social be- 

 havior. A social group is any aggregation of two or 

 more individuals of the same species. A society is a 

 social group in which a cooperative relationship takes 

 place, and a nonsocial population is a social group in 

 which no cooperation exists. A colony is a nonmoving 

 social group, and a band is a mobile one. The op- 

 posite of a social group is a solitary organism. Solitary 

 individuals exist where members of the species are 

 actively antagonistic to one another except during 

 brief portions of the reproductive period. 



NONSOCIAL POPULATIONS 



Members of the same species can be together with- 

 out benefit or cooperation among the individuals. In 

 fact, nonsocial groups can display active competition. 

 This normally is the case in germinating plants that 

 are very close to one another because seeds are con- 

 centrated near the parent. Such germinating plants 

 are in direct competition for the necessities of life, 

 especially space. Also, animals of the same species 

 frequently congregate without any active cooperation. 

 Nonsocial animal populations may form at a common 

 feeding or courting location and may or may not dis- 

 play active competition. For example, if food or 

 mates are plentiful, competition might be insignifi- 

 cant; but if things that fulfill needs are restricted, 

 competition may exist among parts or all members 

 of the nonsocial group. Partial competition might 



take place when only a particular age class or one sex 

 is involved, for example, in courtship where competi- 

 tion might be restricted to males, or in a feeding 

 area where adults ignore one another but drive away 

 or are cannibalistic upon the young. 



SOCIETIES 



Cooperative social groups can be simple to com- 

 plex, temporary or permanent aggregations of a single 

 species; only animals generally form true societies. 

 Temporary societies originate during a particular 

 part of a day or during a particular part of the year. 

 Temporary daily societies are formed by many birds 

 that spend the night in a common roost and feed 

 together in a definite area. Such groups are true so- 

 cieties because mutual protection comes from the as- 

 sociation. Seasonal cooperative groups join for such 

 purposes as migration, reproduction, and local pro- 

 tection. 



Permanent societies also are of many types. They 

 might consist of a single pair of parents, a harem, a 

 family, a clan derived from a single pair of ancestors, a 

 clone derived asexually from a single parent, or a caste 

 society. The true caste society represents the most 

 complex system of social behavior and is limited to 

 insects, mostly termites and ants but also certain 

 wasps and bees. In the most complex caste societies 

 there are kings, queens, potential kings and queens, 

 food storers, workers, and soldiers; most groups are 

 distinguishable on the basis of body form alone. 



The degree of organization of a society is directly 

 proportional to the degree of its leadership and 

 division of labor. Almost any society displays some 

 amount of internal leadership, also called social 

 dominance or "pecking order." The latter term refers 

 to early studies of leadership that were made on 

 birds. In a simple society there usually is an order of 

 dominance among the individuals of the society. For 

 example, in chickens the order is expressed by peck- 

 ing, which may be linear or circular. In linear domi- 

 nance the number one leader dominates all others, 

 the number two leader all except number one, and so 

 on down to the individual that is dominated by all 

 other members of the society. In circular dominance 

 there may be no single leader; each individual of the 

 society is in a single peck order that is independent 

 of all others. Therefore, circular dominance can 

 feature somewhat peculiar relationships. For ex- 



