driven from its territory previously. A few examples 
will help to clarify this point: 
1. During the spring of 1949 male 49 dominated 
the area about the South Alley Burrow and 
its extension in front of Passage 1 . Neverthe- 
less, and despite the fact that he was observed 
in the Food Pen hundreds of times in close 
association with other rats, only once was he 
observed to fight another rat there. On this 
one occasion he chased male 707 out of the 
garbage pail placed there for the purpose of 
photography. Male 707, who was the domi- 
nant male of the neighboring burrow by 
Passage 2, and who was a younger sib of male 
49, was the only male who persisted in invad- 
ing the vicinity of the South Alley Burrow, 
particularly at times when females were in 
estrous. Such a period of invasion occurred 
during the evening of April 25 when the con- 
flict in the Food Pen occurred. Thus, this 
single aggressive action by male 49 outside his 
territory was probably an extension of a specific 
social relationship involving territorial rights 
rather than resulting from competition over 
food. 
2. During 1948 male 22 established Area I as his 
territory and consistently chased out all 
adult males which invaded it. He was also 
a persistent storer of food. On one such trip 
on June 28 he was carrying a large piece of 
cake. Just before he reached Passage 1, as he 
was going up Path 1, the cake crumbled into 
several pieces. He then began making the 
several trips requisite to retrieve the pieces. 
On one of the last trips, while he was still in 
his harborage, adult male 30 invaded Area I. 
The latter was immediately chased out of 
Area I and through Passage 1 by male 22. 
Although male 30 went over a few feet into 
the West Alley, he returned in a few seconds to 
Path 1. There he and 22 sat amicably side 
by side and ate the remaining pieces of cake. 
Here male 22 failed to exhibit any aggressive 
action outside his territory even when a piece 
of food was involved toward which male 22 
might have been expected to exhibit some 
“property rights.” 
3. On May 18, 1948, female 28, who had 31 
day-old young in Area I, stopped and entered 
several holes of the South Alley Burrow. 
While this was going on female 37, who had 
19 day-old young in this burrow, came from 
the Food Pen. She jumped on 28 and bit her. 
The latter fled. Later in the evening they 
were observed feeding together in the Food 
Pen with no show of animosity. Similar 
observations are available for other females. 
There is one main difference between the 
territorial defense exhibited by lactating females 
and that by males with a harem. This is that two 
or more lactating females may simultaneously 
inhibit the same burrow system without showing 
any animosity toward each other. Males exhibiting 
territorial defense rarely permit the presence of 
another adult male. However, when more than 
one lactating female simultaneously inhabits a 
burrow it is characteristic that each confines its 
activities primarily to a restricted portion of the 
burrow. Where a territory was held by a single 
male (such as by 22, 49, or 690) (pp. 198 to 202) it 
was quite apparent that the adult females who 
lived in it were subjected to much less stress than 
females living elsewhere. This was because they 
were bothered less by the sexual advances of males, 
as well as because of the reduced necessity of 
defending a terriotry. 
There was one behavior associated with terri- 
toriality which became highly developed in male 
49 This was the behavior, which I have designated 
as “passage guarding.” It consisted of a passive 
phase in which a rat stood in, against or near a 
passage through the fence. When so blocked, 
any more subordinate individual had to wait for 
the dominant rat to move, or it had to take a more 
circuitous route to its goal. The active phase 
consisted of exhibiting threatening motions, or 
actually giving chase to rats who approached. 
When a territory included a passage, the focus of 
the defender’s attention to that point enabled it 
most effectively to keep away other rats. Passage 
guarding occured primarily at the passages through 
the central barrier fence, although it was occasion- 
ally exhibited at the passages into the Food Pen 
(probably as a sexual response). Two conditions 
contributed to the origin of the passage guarding 
repsonse. They were that chases frequently term- 
inated there, and that these spots were favorite ones 
for the depositing of estrous scent. 
For rats one can make the distinction between 
territoriality and dominance on the basis of exclu- 
sion from a space. Among males it is difficult to 
assign territoriality unless there is complete exclu- 
sion of other males. Among females there must be 
the exclusion of females who are not members of 
187 
