rats grouped about the source of food. Observa- 
tion of such groupings has led me to conclude that 
what appears to be rather complex interrelation- 
ships among members of such groups can actually 
be broken down into paired relationships. Frame 
by frame examination of several thousand feet of 
movie film supports this conclusion. 
The following are the major types of paired 
relationship about the food : 
1 . Two rats approach the food and begin eating 
without apparently paying any attention to 
each other, even though they may move so 
close together that their sides touch. 
2. The two rats may approach each other in the 
recognition behavior of extending their bodies 
and heads until their noses nearly touch. 
This may develop into: 
a. Rats eat side by side paying no attention 
to each other. 
b. Both rats run away. When this happens, 
the two rats may very shortly come back 
and begin eating while paying no attention 
to each other. 
3. When one rat is eating and is approached by 
another, the first rat may initially run away 
and avoid the second rat. This behavior of 
the first rat may be the simple one of retreating 
from an object in motion. This retreat may 
occur even though the approaching rat is 
socially subordinate. 
4. The behavior of the rat that avoids the 
approaching rat, must be qualitatively differ- 
ent depending upon social rank. Normally 
the approaching rat does not give chase to 
the avoiding rat unless the approaching rat 
is a dominant one and the avoiding rat holds 
a subordinate position. The implication of 
such observations is that many conflicts, 
which occur near the food source, do not 
arise as a competitive action over food. In 
fact, where both rats are socially relatively 
high ranking, the frequency of avoidance is 
less and the likelihood of a chase being 
precipitated by the avoidance is also 
decreased. 
5. When two rats come in contact with each 
other by chance movements or as a result of 
a restriction of the distribution of the food, 
pushing behaviors frequently arise. This 
takes the form of pushing with the forefeet, 
kicking with the hind feet, or swinging the 
posterior end of the body at the other rat. 
Both rats may continue eating while engaging 
in this pushing. Following this pushing one 
of the rats may walk away from the food, 
although sometimes upon receiving a push 
a rat will jump sidewise or backward from 
the food. 
6. This pushing may develop into a conflict, 
which interrupts the feeding of both individ- 
uals to the point that they rear up in the 
sparring position and engage in a tumbling 
fight. One rat at least leaves the food source 
and the other may give chase. 
These latter two categories of behavior may be 
considered as different intensities of intolerance to 
crowding rather than to conflicts resulting from the 
food objects themselves. Considering these six 
categories as having covered the basic relationships 
which may exist between two rats, it is apparent 
that as the number of individuals, which assemble 
simultaneously as the food source increases, there 
will be an increased likelihood that any specific 
paired interaction will become more aggravated. 
Furthermore, the opportunity for sequential re- 
actions becomes enhanced. This happens when 
one animal, which jumps away from the approach, 
push, or bite of another, accidentally lands on a 
companion, who in turn may swing aside and bump 
into another rat. At times a group of 10 to 15 rats 
appears to explode. 
There are a number of factors which predispose 
a paired relation toward complete amicableness or 
aggressiveness. These will be discussed in more 
detail later in the sections relating to social be- 
haviors and social organization (pp. 179 to 198), 
since paired relations may occur at many points 
other than at the food source. Nevertheless, my 
notes are replete with instances of rats in groups of 
from 2 to 15 eating amicably together. 
It was stated above that conflicts arising at the 
food source do not arise over competition for the 
food objects themselves. The following two in- 
stances are typical examples which further support 
this belief: 
1. June 28, 1948: Male 22 (440 days of age; 
weight 532 grams) has been transporting food 
to Area I where he is the dominant male. At 
5:50 p.m. he brought a piece of cake up Path 
1, but along the way it fell and crumbled. 
This caused him to make several trips to re- 
trieve it. On one of these trips back into Area 
I he encountered male 30 (317 days of age; 
weight, 474 grams) who had just invaded 
101 
