of attaining sexual maturity, 86 to 115 days of 
age. 
One of the most potent social forces affecting 
juveniles and tending to reduce the likelihood of 
them remaining at home was the action by their 
mothers. Between the ages of 60 and 85 days the 
young were frequently chased away from the 
vicinity of the home burrow by their mother. The 
juvenile might be caught up with, knocked and 
rolled over, whereupon it squealed, but the rarity 
of wounds on rats of this age indicates that they 
were rarely bitten in the process. This action by 
the mother may occur whether or not she is 
lactating or pregnant. 
However, lactating females sometimes become 
particularly antagonistic to all juveniles over 46 
days of age. I have not observed this increased 
antagonism against juveniles under this age. If 
this absence of aggression by lactating females 
toward juveniles between the ages of 25 and 45 
days is actually true, it will certainly have survival 
value for the young, in that following that age they 
will be better developed physically to meet the 
exigencies of the environment. 
Adults of both sexes show antagonism toward the 
juveniles at the source of food when the latter 
make too frequent incursions upon their feeding 
activities. During its first few trips to the food 
source, a 30-45-day-old rat will dash among and 
over adults who are feeding. This dashing ac- 
tivity by the juvenile in itself is sometimes disturbing 
to an adult feeding aggregate, because they have 
come to associate rapid motion (p. 179) with the 
occurrence of interadult strife. Furthermore, the 
juveniles will push right in and take away food from 
the adults. Although this action may be initially 
ignored, it is usually followed by the adult pushing 
the juvenile away with its fore or hind feet. If the 
intrusion of the juvenile continues, as it usually 
does at this stage, the adult will turn on it more 
vigorously. In this process the adult may knock 
the juvenile over and give it a thorough trouncing 
with all four feet. 
Up until 50 days of age (see fig. 122) the juveniles 
are never bitten by the adults. In fact, it is ex- 
tremely rare that the juveniles are ever bitten by 
adults under any circumstances, even up to the 
age of 86 days when sexual maturity begins to 
develop, despite the apparent severity of the 
thrashing or fight which develops. Because of the 
usual absence of wounds received by juveniles in 
this process of social conditioning by adults, I have 
termed this category of actions as “psychological 
drubbing”. That this action is effective soon be- 
comes apparent. Even as early as 45 days of age 
a young rat will run and sometimes squeal as an 
adult wheels toward it. Certainly during the 
period between 86 and 115 days, when the juvenile 
is rapidly developing sexual maturity, this avoid- 
ance behavior toward the threats of adults is 
apparent in all rats. The juveniles not only learn 
to avoid the threats of adults, but they also learn 
to avoid expressing those behaviors which would 
elicit the antagonsim of adults, such as attempting 
to take priority over a particular morsel of food, 
or in pushing an adult away from a passage through 
the barrier fences. 
The social conditioning of the young encom- 
passes considerably more than the adjustment to 
the priority rights of older rats as a result of the 
psychological drubbings. These other aspects of 
social conditioning, whereby the young rat comes 
to express adult behaviors and becomes integrated 
into the adult society, mostly stem from a gradual 
transition of the mother-to-young relationships into 
those of adult-to-adult relationships. As soon as 
young rats engage in movements outside of the 
burrow, independent of being transported from 
place to place by its mother, they may be seen 
closely trailing their mother. An example is as 
follows: 
On June 1, 1948, female 37 who had conceived 
2 days previously was observed transporting food 
up Path 1 and over into Area IV near Box 29, 
where she had recently shifted her place of residence 
from the South Alley Burrow. Two of her 30-day- 
old young were seen trailing her in an apparent 
attempt to grasp a teat. 
There are two important behaviors here. First, 
there is trailing. Second, there is the oral inspec- 
tion of the posterior ventral region of the mother. 
Whereas trailing is most commonly observed with 
reference to the mother, it may also be observed 
very early with respect to other animals. The 
manner in which this shift may be made is exempli- 
fied by the instance in which one of female 37’s 
31 -day-old young was following her from the Food 
Pen toward Area IV. Along the way adult male 
22 crossed between them, whereupon the young 
rat followed him for a few feet. I strongly suspect 
that it is such accidental following of mother sub- 
stitutes which leads to the occasional harboring of 
a 35- to 40-day-old juvenile rat with some other 
adult than its mother at the time the mother is 
149 
