arc in front of the dominant rat. These gross 
behavioral differences must make it rather easy for 
one rat to detect the rank of another. 
The second circumstance eliciting avoidance 
behavior is the rapid approach of one rat toward 
another. This situation is one in which one rat, 
which is eating, or drinking, or is engaged in some 
other stationary activity, is approached from the 
rear or from one side by another rat in rapid 
motion. The rat which is being approached 
frequently dashes away for at least a short distance, 
regardless of whether it is lower or higher in rank 
in comparison with the approaching rat. This 
holds true for all but the very highest ranking rats. 
The critical point to note here is that the rat which 
does the avoiding does not have the opportunity 
to make any discrimination regarding either the 
individuality or rank of the approaching rat. By 
running to one side it gains the opportunity to 
examine the situation and decide whether to 
return or continue in fleeing. 
The avoidance behavior of the first type discussed 
above appears to become elaborated to the extent 
that the presence of the dominant rat is not re- 
quired. After a rat has experienced many threats, 
chases, or losses in combat at a particular place the 
same vacillating, and hesitant approach and with- 
drawal is elicited even in the absence of any other 
rat. This sort of behavior with reference to entering 
the Food Pen, as well as that of carrying food from 
the hopper over into a corner of the Food Pen to 
eat, probably have their origin in the avoidance of a 
dominant by a subordinate rat. Each of these 
behaviors comprise aspects of the syndrome of the 
social outcast (pp. 195 to 196). Male 8 ex- 
hibited these behaviors in 1947 as a result of his 
experience with the then dominant male 12. The 
latter in 1948 after having become subordinate to 
some of the younger, more vigorous adult males also 
exhibited it. 
c. The combat. Juvenile rats at least up until the 
initiation of sexual maturity, 85-115 days of age, 
engage in what may be termed “mock-combat.” 
They exhibit nearly the full repertoire of actions 
including preliminary periods of boxing in which, 
while standing on their hind legs and bracing 
themselves with their tails, they knock at each 
other with their forefeet. This is frequently fol- 
lowed by a brief episode of rolling and tumbling 
over each other in which the participants appar- 
ently hold on to each other, although this apparent 
holding may simply be the act of one rat closely 
following the escape movements of the other. The 
reason that such encounters are thought to repre- 
sent “mock-combat” or play is that terminating 
the action each goes about its own activities without 
any show of aggression or avoidance. In fact they 
may even sit near each other and groom. Fur- 
thermore, although two juveniles who have been 
caught in the same trap together may fight viciously 
upon the observer’s approach, there is rarely any 
evidence that wounds are received in such en- 
counters. Thus, there may be both lack of ability 
as well as lack of intent to injure among young 
rats. The low prevalence of wounds among young 
rats is shown in figure 122. 
This “mock-combat” behavior gradually is 
transformed into real combat through the inter- 
action with older rats. A typical case is as follows: 
On July 6, 1947, 370-gram, 320-day-old, dominant 
male 12 was seen at the North Alley Burrow boxing 
with 293-gram, 81-day-old male 21. At first, they 
stood up facing each other while boxing without 
moving out of their tracks. Finally male 12 forced 
male 21 over on his back and the boxing continued 
such that male 21 kept pushing away male 12 who 
was leaning over. Male 21 was held on his back 
for 15 seconds. Finally, one of the rats must have 
taken a bite at the other for there was a squeal 
followed by 21 running away, while 12 remained 
and groomed for several minutes. Although male 
21 may have experienced some punitive action in 
this encounter, the mild character of the combat 
may be judged by comparing it with the following 
account of a combat between two adult males. 
A frame-by-frame examination of the filmed 
sequences of combat taken by the U.S. Army Signal 
Corps at the Towson plot enabled a very accurate 
description of the sequence of events occurring in 
combat. The following is the best such account 
available. The action occurred at the North 
Alley Burrow, during April 1949 in the presence of 
an estrous female: The scene begins with two adult 
males peering down into a burrow entrance 
through which an estrous female had just escaped 
their advances. The rat on the right just slightly 
throws his hip at the left male, which at first moves 
slightly away and then several feet away. Al- 
though the remaining male examines the entrance 
intently he does not engage in any sexual rolling. 
All of a sudden this male jumps up in the air, ap- 
parently as a result of being nipped by the estrous 
female, whose head can be seen for two frames 
while the male is in the air. At this time the other 
180 
