inhabiting the more distant areas. Inexperienced 
young rats inhabiting the areas were at a particular 
disadvantage when they had to pass near the place 
of residence of adults in the alleys, who had al- 
ready developed a dominant status. Rats living 
farther from a goal were also forced to expend 
more effort in satisfying their needs. This greater 
demand on the individual’s physiology presumably 
places it at a disadvantage. 
b. Size and age: Larger and older individuals 
regularly win when open conflicts develop between 
two rats. Furthermore, the smaller individuals, 
regardless of age differentials, most frequently 
exhibit avoidance of other rats. 
c. Social genealogy: Rats born in colonies, whose 
adult members more frequently exhibit submissive 
behavior to members of other colonies, in later life 
also tend to exhibit submissive behavior. Thus, 
even in the absence of observed status-revealing 
interactions, the origin of a rat is taken as a 
criterion of social rank. 
d. Place of residence and associates: Rats frequently 
depart from their place of residence and take up 
residence elsewhere. The past history of the 
inhabitants of the area in which they become 
established serves as a criterion of social rank. This 
is a particularly good criterion with respect to 
whether the invading rats displace the residents or 
are amalgamated into the resident group. In any 
case an invading rat develops new associations, 
which may include those with rats which have 
arrived from several places of birth. The more 
unfavorable are the places of origin represented by 
the members of a group, the lower is its assigned 
social rank. Furthermore, the more places of 
origin that are represented by the members of a 
group, the lower is the assigned social rank. See 
the discussion of the homogeneity index (p. 214). 
It was certainly apparent that when there were 
several places of origin represented in a group its 
members were less successful in satisfying their 
needs. 
e. Competition during early life and rate of growth: 
Young rats which are exposed to contacts with 
other young and adults have their growth rate 
inhibited in proportion to the frequency of contacts 
with their associates. Growth rate is particularly 
inhibited if these associations are with older 
unweaned sibs of a prior litter who are not yet 
weaned, or if the associations occur between the 
time of weaning at about 35 days and attainment 
of sexual maturity between 85 and 100 days — that 
is during the postweaning juvenile period. This 
latter also is the period when “psychological 
drubbings” of juveniles by adults occurs. Thus, 
the relative frequency and type of associations is 
taken as an indication of later social rank, particu- 
larly with reference to the degree of inhibition of 
growth. 
f. Observed outcome of combat: Adult males, particu- 
larly those born in colonies under favorable condi- 
tions, fought for the right to remain at the place of 
birth, or at some other place which was still favor- 
able in relation to other existing locations. It is 
patent that few of these adult males could attain 
the dominant status. Thus, despite their large size 
and potential ability to win over smaller males 
inhabiting less favorable localities, many of these 
males eventually were forced to reside with smaller 
males, which were characterized by less favorable 
early history. Despite their larger size and more 
favorable early history, these males which were 
excluded from the more favorable places of resi- 
dence, never seemed to be able to develop a clear- 
cut dominant status over their smaller associates. 
It was because of this sequence of events that size 
alone is not a valid criterion of social rank. These 
events apply similarly, but jess frequently to 
females. 
g. Sex ratio of the colony: The fewer males there 
are in a colony in proportion to females, the greater 
is the likelihood that (a) the individuals will on 
the average be larger, (b) the reproductive success 
will be better, (c) the individuals will have had a 
more favorable earlier history, and (d) in the case 
of combat with members of other colonies the 
members of such colonies will win. In some cases 
the past history of a group, which now has a favor- 
able sex ratio, will have lead to its higher social 
rank, even though it lives farther from the food 
source For example, refer to the discussion of. 
colony c in Area III in comparison with colonies 
g, j, and k in the North and East Alleys as they 
existed in the spring of 1949 (pp. 206 to 213). 
This is a case where the criterion of proximity to 
the food source is overridden by other conditions 
in the past history of the groups. 
h. Reproductive success: The conception rate and 
the ability of females to rear young to weaning 
both reflect social rank. However, this may be 
judged only by the average performance of the 
females in a colony. When the average perform- 
ance is high, this is taken as a criterion for all the 
rats in the colony, both males and females. 
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