DISCRETE COLONIES- SPRING OF 1949 
W AREA IV social rank AREA I S 
high E3 
MEDIUM □ 
LOW □ 
Figure 128. — Discrete colonies during the spring of 1949. 
See tables 44 to 56 for characteristics of the members of 
these colonies. 
2. Number of places of birth represented by 
members of the group. The more places of 
birth, the lower the social rank of the group 
(see p. 214). 
3. The location of the colony. This takes into 
account the whole history of the population, 
which indicated that the southeast (particu- 
larly the south) side of the pen was the favored 
region, and that proximity to the food source 
favored high social rank. 
4. The proportion of the group formed by fe- 
males. The higher the proportion of females, 
the higher the social rank of the group. 
5. The reproductive success of females on the 
basis of number of conceptions and success- 
fully weaned young. 
6. The number of wounds. 
On a rather intuitive basis these criteria were 
weighted to form the ranking of the colonies from 
a to k in a descending order of social rank. See 
tables 44 to 48 and 50 to 55, and figure 128. 
Explanation oj tables 44 to 57. S.A.B. and N.A.B. 
refer to birth at the South and North Alley Burrow. 
1 he Maturity Index reflects the mean growth rate. 
At each time of capture each rat was assigned as 
being characterized by rapid growth (I), moderate 
growth fll), or slow growth (111). These readings 
were averaged to give a Maturity Index which 
most nearly reflected the growth rate of the rat 
during its entire life span. Thus 1.38 represents 
greater than average growth rate while 1 1. 10 
represents slight less than average growth rate. 
For further details on growth and this index see 
pages 216 to 236. The May 1949 weight for 
certain females is shown in italics. These rats 
were pregnant. Their weights were excluded in 
deriving data pertaining to weight in tables 55 and 
56. Information on placental scars is incomplete 
since the uteri of only a portion of the females were 
were preserved for later counts. 
a. General Remarks about the Colonies as they Existed 
in the Spring of 1949. 
Colony a: South Alley Burrow — {table 44, fig. 21). 
An appreciation of the formation of this most 
favored colony requires consideration of those rats 
who were born here but later emigrated. None of 
the 22 males which were born here in 1948 and 
which survived into the spring of 1949 remained 
here. See comments under prior discussion (pp. 
199 to 200) of the dominance of male 49 for 
some of the reasons for their dispersal. Also see 
the comments under colony i for the males who 
remained as marginal members. I was never able 
to determine why some of the females born at the 
South Alley Burrow remained, whereas others 
emigrated. Among those which bore litters, there 
was no difference in growth and maintenance of 
weight between those who remained and those who 
emigrated. However, 78 percent of these females 
who remained in the southeast half of the pen 
successfully reared young, whereas only a 50 percent 
success characterized the females who emigrated 
(table 31). Some of the characteristics of this 
colony, not included in table 44 are: 
1 . The entire past history of this colony indicated 
a most favored status. 
2. The females were protected by the single most 
dominant male of the pen from excessive dis- 
turbance by other males. 
3. The rats of this colony, with their more stable 
social structure, were able to maintain the 
physical structure of their burrow. Compare 
figures 21 and 22 and the remarks under 
colony j. 
Only 3 of these 13 females failed to have any 
surviving young at the end of May 1949 which were 
bom during the preceding spring breeding season. 
Two of these, 778 and 704, had exhibited the 
204 
