LIFE HISTORY 33 



arthropods, and Mollusca. Homing intelligence is especially impor- 

 tant; thus, ''tradition" plays its part in the choice of areas of winter- 

 ing, as in the Kaibab deer (Rasmussen, in MS) . At the same time the 

 habits of animals during the earlier part of their life histories are 

 commonly molded to some degree by their community associates and 

 habitat conditions. The mores are thus, in part, a community prod- 

 uct. There is unquestionably some teaching of young among birds 

 and mammals, as in the coyote (Bailey, 1930). Social organization 

 of wolves leads to the formation of pack hunts and to the establish- 

 ing of regular routes of travel. Ungulates also assemble in herds with 

 some degree of organization. In Africa, where there are many species 

 with great numbers of individuals and where mixed herds occur, the 

 danger signal of any one species may serve to warn the entire herd. 

 In similar fashion, sheep and goats post sentries in outlying positions 

 to give alarm at the approach of danger (cf. Roosevelt, 1910; Holmes, 

 1911). 



In addition to all these activity phenomena, plastic and moldable 

 by community contacts, there are many similar responses which result 

 in "regulating" the organism into a suitable situation. When the 

 organisms find themselves in unsuitable and thereby stimulating or 

 irritating conditions,, random movements and activities take place, 

 some one of which relieves the irritation, and the organism comes to 

 rest. In addition, practically all animals possess a capacity for ad- 

 justment, e.g., metabolism and temperature regulation characterize 

 warm-blooded animals especially. There is also regulation wdth refer- 

 ence to respiration, neutrality, water, and osmotic pressure. All these 

 call into play behavior, muscular activity, and special organs not 

 found in plants, and serve to illustrate the greater emphasis which 

 must be laid on activities and physiological processes in animals as 

 compared with plants (Shelford, 1911, e, 1913, a). 



LIFE HISTORY 



Definition and Significance. Life history is the life cycle of the 

 individual; it embraces the entire round of activity or behavior from 

 birth to death. It is not only a cycle in its complete expression, but 

 it also often includes minor cycles corresponding to those of the day, 

 season, or year. These serve to mark the phases or stages of what 

 is essentially a continuing process, and hence organize and illuminate 

 the host of details that constitute the round of life. Embryonic stages, 

 though an intrinsic part of a life history, are best treated in the 

 specialized fields of embryology or morphology, with the possible 



