male reapproaches the hole. He is very close by 
the time the nipped male lands on the ground. 
They extend their necks and bodies until their 
noses are about an inch apart (their vibrissae seem 
to touch). Then the male with apparent priority 
again sticks his head down the entrance, while the 
other male gradually approaches and does likewise. 
Upon this crowding the dominant male swings his 
head toward the other male, who begins to rear up 
on its hind legs, while he uses his right forefoot to 
fend off the dominant male. Then both rear 
nearly straight up. The right forefoot of the left 
rat (the submissive one) fends off the left forefoot 
of the right rat (the dominant one). Their heads 
then approach until their teeth appear to be in 
contact (this lasts for not quite two frames). The 
power exerted by the hindlegs seem to be critical 
at this point. The greater force exerted by the 
dominant rat throws the other rat over. As the 
submissive rat lands partially on its forefeet and 
partially on its side, the dominant rat appears to be 
biting it on the midback. Whereupon the sub- 
missive rat whirls his head back to the right at the 
head of the dominant rat, but the dominant rat 
pushes him flat on his back with his forefeet, and 
then strikes at the submissive rat’s genital region 
with his teeth. At this point the submissive rat 
begins to roll over and the dominant rat continues 
his biting on the posterior sacral area. The sub- 
missive rat completes his roll, breaks, and runs 
away. The total elapsed time of this action, from 
the dominant rat swinging his head toward the sub- 
missive one to the breaking away of the latter, was 
1.5 seconds. This shows the value of moving 
pictures in describing and interpreting behavior. 
The dominant male then turned back to the bur- 
row entrance from which the estrous female was 
beginning to extend her head. The scene closed 
with the dominant male just initiating a true 
sexual roll. 
Observation without the aid of the camera 
supports the belief that this account is exceedingly 
typical. There is nearly always an initial threat. 
This threat may include one or all of the following: 
1. Whirling of the head and/or body toward the 
other rat; 
2. The prancing approach toward the other 
rat; or 
3. Sidewise motion toward the other rat, against 
whom a hip is thrown. 
These threats are followed by a momentary or 
prolonged (in terms of seconds) period of boxing. 
Although contact, or impending contact, may be 
broken off at any point with the more submissive 
rat running away, the interaction is frequently 
terminated by the rolling over of the two rats 
while still in contact, the emission of a squeal, 
and the fleeing of one of the rats. It is at this 
breaking away period, when the posterior region 
of the submissive rat is exposed to the dominant 
one, that most wounds must be received. Most 
of the several hundreds of records actually state 
that the wounds were on the lumbar-sacral region. 
In fact it was the V-shaped area from the mid- 
back posteriorly over the sacrum and hips which 
in many mature males was characterized by much 
scar tissue. Fewer wounds occurred over the 
shoulders, and there was only an occasional wound 
about the head. Wounds on any portion of the 
ventral aspect of the head, body, or legs were 
extremely rare. 
d. The Chase. One rat giving chase to another 
may precede combat. When the chase terminates 
in a combat, all the preliminaries such as boxing, 
or hip throwing fail to occur. Instead, as soon as 
the pursuer catches up with the pursued there is 
a brief tumbling fight following which the loser 
flees. Chases may also follow a combat. In such 
chases, as well as in chases involving no fights, it 
frequently happened that the rat being pursued 
made successful its escape. It often happened that 
the pursued was younger and more agile. This 
enabled it to out-maneuver and out-distance the 
pursuer. The most frequent type of place where 
chases broke off was at the passages between the 
alley and areas. There were two main reasons 
why the breaks developed at these points. 
Because of its initial head-start, or because of 
its greater speed the pursued rat would reach and 
pass through the passage from the alley toward 
the areas before the pursuer arrived. Here it 
was forced to turn left or right into one of the 
adjoining areas. The pursuer could detect this 
change in direction through the fence and would 
reorient its route of travel correspondingly. This 
reorientation would deflect the line of travel of 
the pursuer away from the passage with the result 
that the chase usually terminated after the two 
ran parallel for a short distance on opposite sides 
of the fence. Such an example is shown in figure 
121 . 
A second factor influencing the termination of 
a chase at these passages was that they served as 
a sexual signpost. The pursuer frequently ceased 
181 
