ANIMAL AGGREGATIONS 



417 



behind. This is a handicap during winter, 

 especially in large herds; in iact, ni winter 

 herds of 4000 or 5000, rear reindeer are 

 always weak and badly nourished. 



Middle reindeer are more quiet, peace- 

 ful animals, and they suffer less from pred- 

 ators than do those from the fringes of 

 the main herd. 



Within these different groups, more 

 closely knit bands often occur that may 

 have as many as thirty animals, but are 

 generally smaller. They are formed by kin- 

 ship or apparent friendship relations, and 

 each such subgroup has an old female as 

 a leader. They account for only a minority 

 of the herd; most reindeer keep on their 

 own within their general subdivision of the 

 herd. 



The territoriahty shown by such aggrega- 

 tions is based on position with regard to 

 associated animals, rather than to topo- 

 graphic or other features of the environ- 

 ment. The full extent to which such terri- 

 toriality occurs elsewhere in the animal 

 kingdom is a matter for investigation. 



Leadership allows greater flexibiUty of 

 behavior than is usual in territorial or hi- 

 erarchal organizations. Territory and lead- 

 ersliip both have fairly obvious survival 

 values. The biological values associated 

 with the system of social hierarchies are 

 more obscure. It is easy to demonstrate in- 

 dividual selection accompanying high 

 status in the social order, but the group 

 survival values growing from this type of 

 social organization, as such, have not yet 

 been adequately analyzed. 



At the individual level, highest ranking 

 individuals in a social hierarchy lead the 

 freest Hves; they have more ready access 

 to food and mates and to habitat niches. 

 High ranking hens lay more eggs (Sanc- 

 tuary, 1932), and cocks with high social 

 status mate more frequently (Guhl, Col- 

 lias, and Alice, 1945) and sire more chicks 

 (Guhl and Warren, 1946). Similar rela- 

 tions hold in many penned mammals (cf. 

 Cooper, 1942, for lions) and probably also 

 in nature (cf. Carpenter, 1942, for rhesus 

 monkeys). Conversely, low position in the 

 social gradient carries restrictions that may 

 be severe or even fatal in extreme cases. 



We have no data as yet on the short-run 

 or long-run success of relatively unorgan- 

 ized groups of animals in comparison with 

 other groups of the same species arranged 



in a dominance hierarchy. Some critical 

 work indicates that accepted social status, 

 whatever tlie ranks involved, confers values 

 not found in a group undergoing organiza- 

 tion or reorganization. As an illustration, 

 the sage grouse of Wyoming and other 

 western states presents a modification of 

 the habit of mating in restricted localities. 

 The males assemble at each mating place 

 in early spring and organize themselves 

 with a "master cock" that does most of the 

 copulating; "subcocks" are less successful 

 socially; "guard-cocks" are still less active 

 in mating; and the remaining cocks, con- 

 stituting the majority of the entire male 

 population, do little breeding (J. W. Scott, 

 1942).*' 



In one instance the cocks of a certain 

 mating place shifted ground as a result of 

 snow. This brought them near another set 

 of mating males, and fighting continued 

 through the usual mating hours. Females 

 coming to the mating places with the first 

 dawn, collected in numbers about the area 

 where much fighting was in progress. Later 

 in the morning, as the fighting between 

 the males continued, the hens tended to 

 move oflE to a mating place that was well 

 organized and quietf (see Guhl and Allee, 

 1944). 



Groups of common domestic hens also 

 show survival values related to quiet, or- 

 ganized hierarchies. Members of such 

 Hocks accept their usual social status, and 

 there is much less tension than exists in 

 flocks undergoing reorganization with con- 

 tinued strife. The hens in the organized 

 flocks pecked each other less, consumed 

 more food, maintained weight, and laid 

 more eggs. These are quahties that might 

 well have survival value in nature. Appar- 

 ently the social organization in such groups 

 is of importance, less as an end in itself 

 than as a means of reducing fighting and 

 other extremes of social tension. 



There is justification for thinking that 

 these laboratory findings are indicative of 

 certain conditions in nature. If so, individ- 

 ual-against-individual competition, such as 

 results in the peck-order type of social or- 

 ganization, may help to build a social unit 



* These are the relations Scott has reported 

 more than once, yet in the absence of banded 

 birds, he is not completely sure how long a 

 given individual remains in a given social rank. 



f Personal communication. 



