boxing. The same male or another male would 
then follow and mount. Even when the female 
was in this receptive phase, successful copulation 
did not necessarily occur. At least the female 
might break away without exhibiting lordosis. 
Occasionally the signal for the stopping by the 
female is the stepping on her tail by the male. 
When the male was still standing on her tail as she 
pulled from under him, he was likely to be upset 
as he bent over to grasp his penis. 
Two to twelve males might pursue the female in 
a relatively compact pack. As soon as one male 
mounted, the others merely stood around and 
watched, or wandered off to roll at a burrow 
entrance. There was never any attempt by one of 
these males to interfere with the male who had 
mounted. Yet they frequently fought when two 
males simultaneously attempted to roll at a burrow 
entry, where the female was hiding. 
Where a single male dominates a burrow system, 
he is able to keep away most other males. An 
occasional male from surrounding colonies is able 
to avoid the dominant male and copulate with the 
receptive female. However, the actions of the 
dominant male both reduce the number of mount- 
ings while she is receptive, and effectively preclude 
other males bothering her after she is no longer 
receptive. When there are relatively few adult 
rats, as was the case during the 1948 breeding 
season, a female who is sexually attractive to males 
is not unduly bothered by them, even though there 
is no dominant male residing near to her place of 
harborage. The female can either avoid the few 
males or repulse their advances. 
However, when there is no clearly dominant 
male at the burrow inhabited by a sexually attrac- 
tive female, and when many males live in the vi- 
cinity, the fate of the female is quite otherwise. 
For the rest of the night, at the beginning of which 
the female is first receptive to being mounted, a 
pack of 2 to 12 males will be in continuous pursuit. 
This pursuit continues after she has ceased being re- 
ceptive. That receptivity does decline is indicated 
by the fact that after a number of consecutive 
mountings she begins aggressive action toward 
the males. She will not only pull out from under 
a male, who has begun to mount her, but she will 
wheel around, box, and even attack and bite the 
male. Even so, many males succeed in mounting,' 
although the frequency with which she exhibits 
lordosis declines. Between each mount or small 
group of mounts or attempted mounts she retreats 
into the burrow. As soon as she enters, the pack 
of males who were in close pursuit, immediately 
scatter to adjacent entries. In this way nearly 
every possible route of escape by the female is 
covered by at least one male. It is at such times 
that fights most frequently occur between males as 
two vie for the right to exhibit sexual rolls at the 
same burrow entry. As mentioned elsewhere (pp. 
183-148) this aggressiveness becomes transferred to 
other places in the pen. Males who are not in- 
volved in direct competition over the female, nor 
who have even exhibited sexual activity of any sort, 
receive the brunt of the aggression of males, whose 
sexual activity and aggressiveness have been height- 
ened as a result of the presence of a female who is 
sexually attractive. Thus, young males and adult 
males not involved in the sexual activity were fre- 
quently attacked in the Food Pen. Among those 
males in the sexual pack there was frequently clear- 
cut differentials in the ability to win combat, yet 
territoriality was absent. This situation, when 
compared to that where there is a dominant male 
exhibiting territorial defense, suggests that hierar- 
chical organization without territorial defense mav 
actually be detrimental. 
When the female emerges she is immediately 
covered by a male, and the rest of the pack join the 
pursuit, until she again enters the burrow. Often 
the male at a burrow entrance may be seen to 
bounce up into the air as the female sticks her head 
out and nips him. The exact number of mountings 
or attempted mountings per night is unknown, but 
it must approach a thousand. Normally the males 
in a pack do not enter the burrow, but if the female 
stays in too long one will venture in and force her 
out. Practically all of this activity occurs in the 
immediate vicinity of the female’s home burrow. 
Only rarely does she get the opportunity to go to 
the Food Pen, and even then, males who paw and 
inspect her genital region or attempt to mount, 
give her little opportunity to eat or drink. There 
can be little doubt that this sequence of events 
produces a marked stress on the female’s physiology. 
Under the topic, “Stress and Reproduction” (p. 
214) it is pointed out that females exposed to such 
intense action by males have a slightly reduced 
number of conceptions, and practically none of the 
young conceived are raised. 
The description of most of the sexual behavior 
described above was facilitated by the frame by 
frame examination of several thousand feet of film 
taken by the U.S. Army Signal Corps. 
155 
