There is reason to suspect that the socially lower 
ranking rats in addition to engaging in fewer posi- 
tive encounters also engaged in fewer neutral social 
interactions. This belief is based upon the regu- 
larly observed fact that rats of known low social 
status customarily became active when most other 
rats had retired to their burrows. However, this 
tendency toward a reduced number of total social 
interactions characteristic of socially low-ranking 
rats must have been reversed following the invasion 
of the northwest half of the pen by rats forced from 
their place of birth in the southeast half of the pen 
by early in the winter of 1948. I, furthermore, 
strongly suspect that it was an attempt to reduce 
social interactions as much as possible that led to 
the formation of all male aggregates in the spring 
of 1949. The members of these groups were such 
definite outcasts that they never engaged in sexual 
relations with females. 
H. History of Male Dominance. The largest of the 
introduced males, No. 6, was clearly the dominant 
male until his death from unknown causes on July 
19, 1947. There was nothing in his behavior to 
indicate defense of territory; there was merely an 
expression of dominance in fighting encounters, 
wherever they might occur. 
His presence for two-thirds of the time in the 
southeast half of the pen during this time may well 
have been an important factor in making this half 
of the pen the more favored one in the latter history 
of the colony. Following his death there remained 
only two of the original males, Nos. 8 and 12. 
Marked antagonism existed between these two indi- 
viduals although it took the form of male 8 avoid- 
ing male 12 whenever possible, and male 12 attack- 
ing male 8 whenever they met. There was never 
any expression of tolerance between them. This 
complete lack of tolerance was never noted for 
males born in the pen, and it is therefore assumed 
that this lack of tolerance may be attributed to the 
lack of opportunity of developing mutual adjust- 
ments of noncombative behavior during early life. 
All introduced rats, if not actually total strangers, 
were strangers in the sense that they were thrown 
into a new environment in which there were no 
previously established priority rights to places and 
objects, I hus, the initial adjustment was one of 
fighting to establish priority rights. This initial 
behavior was the one which then became the estab- 
lished one when any two of the introduced males 
encountered each other, and probably accounts for 
die relatively greater antagonism which occurred 
among the introduced rats, both male and female. 
This marked antagonism among the colonizing 
adults during 1947 was also extended to encompass 
many of the relations between these adults and the 
young born during 1947. After male 12 assumed 
his dominant status during July he persistently 
fought or chased young males between the age of 
60 and 200 days. This lasted until the cessation 
of sexual activity in late October 1 947. I strongly 
suspect that it was this extreme punitive action 
received by these young rats, who became the adult 
males of the 1948 season, that inhibited their ex- 
pression of any clear-cut territorial dominance in 
most areas inhabited by breeding females. Fur- 
thermore, these experiences probably contributed 
to the lessened antagonism of adult males toward 
juvenile and subadult males during 1948. 
Male 12 also can hardly be said to have had a 
territory unless his territory was nearly the whole 
pen. During most periods of observation he was 
seen to wander leisurely over most of the pen, and 
1 night he was seen to cover every portion of the 
pen. No rat born in the pen was seen to exhibit 
such an extensive home range. When both cap- 
tures and visual observations of his presence were 
included he exhibited the following distribution: 
southeast half of pen, 43 (South Alley, 14; Area 1, 
17; Area II, 12); northwest half of pen, 25 (North 
Alley, 12; Area III, 3; Area IV, 8). These records 
are for the period March 27 to October 29, 1947, 
which approximates the breeding season. How- 
ever, trapping records (fig. 107) which more 
closely approximates places of harborage indicate 
a strong preference for the southeast half of the pen. 
During the nonbreeding winter season of 1947-48 
male 12 lost his prior dominating status. By 
April 17, 1948, when he was approximately 605 
days of age he was emaciated and arthritic to the 
extent of having a permanently arched back. 
There was much scar tissue and fresh wounds over 
his lumbar region; his pelage was extremely 
sparse; and he had only one descended testis, which 
was no more than 10 mm. long. From this time 
until his last record on October 28, 1948, he showed 
a marked shift in his place of residence (fig. 107). 
During April, May, and June he lived mostly in 
Area III. His presence there during the time 
female 43 was rearing her litters Nos. 8, 13 and 18 
at least reflects the lower social status shared by 
other rats inhabiting this northernmost portion of 
the pen. To what extent he also served to mold 
the behavior of the young of female 43, 1 do not 
198 
