Area I. Male 30 normally inhabited the ad- 
joining Area IV. Male 22 chased male 30 
out of Area I. By the time male 22 got back 
to the pieces of cake on Path 1 male 30 was 
there eating. Male 22 joined him and they 
ate amicably. 
2. May 19, 1948: Female 37 (276 days of age) 
has a litter in the South Alley Burrow. Her 
littermate, male 34, who had been living at the 
South Alley Burrow but shortly shifted his 
harborage to other places in the pen, and 
female 28, another littermate whose home was 
now in Area I, both approached the South 
Alley Burrow. Both were chased away by fe- 
male 37. A few minutes later these three rats 
were seen to be eating amicably together at 
the pile of garbage in the Food Pen. 
The point which I wish to make is that conflict 
arises not over the food object itself but results 
rather from crowding. About the place of cus- 
tomary harborage the threshold of tolerance to 
crowding is low, with the resulting expression of 
territorial defense. At a distance from the har- 
borage, such as at the food source, the tolerance to 
crowding is so high, that normally physical con- 
tact, followed by pushing, is requisite to initiating 
conflict to the extent of fighting. An intuitive hy- 
pothesis derived from such observations is that the 
threshold of tolerance to crowding is directly pro- 
portional to the distance from the harborage 
The home range of each animal may be thought 
of as being gourd-shaped with the neck of the gourd 
ending over the Food Pen. Where other conditions 
have enhanced the expression of territorial de- 
fense about its harborage, there is a tendency for 
this heightened aggression to be expressed about 
the approaches to the Food Pen as well as within 
the Food Pen itself. Details of this type of ag- 
gression are given later in the paper (pp. 183 to 
184). 
In my notes there are only five records of simul- 
taneous attention to a single piece of food by two 
rats. These occurred after one of the rats was 
already in possession of the food : 
1. A 102-day-old male from the North Alley 
Burrow took a piece of food away from a 316- 
day-old female at the South Alley Burrow. 
She relinquished the food and walked away as 
if nothing had happened. 
2. A 105-day-old male took a piece of cake away 
from 443-day-old male 22 at an entrance to 
the Food Pen with no show of antagonism 
upon the latter’s part. 
3. At the North Alley Burrow 282-day-old 
lactating female 42 ran out and had a tug-o- 
* war with a young rat which was attempting 
to transport a piece of food away from the 
burrow entrance. 
4. Female 37, who was in estrous, took a roll 
away from an adult male as he was ap- 
proaching one of the passages through the 
Food Pen. The male was probably a sib of 
female 37 and both lived at the South Alley 
Burrow. No antagonism was shown by the 
male. 
5. An adult rat dragged a ham bone to the South 
Alley Burrow but it was too large to be taken 
down into the burrow. A much smaller rat 
approached the bone every time the adult 
went down in the burrow but retreated each 
time the larger rat came back out. 
The meagerness of these observations indicates 
the infrequency of joint action over a piece of food. 
In the Food Pen several rats frequently ate simul- 
taneously from a large piece of garbage. 
A socially low-ranking rat, while transporting 
food to its harborage, may be chased by another. 
Usually the rat being chased drops its food. Oc- 
casionally the rat doing the chasing may return to 
eat or transport the food to its own harborage, 
but more often the food will be left until such time 
as some other rat encounters it. Involvement of 
food in the conflict situation appears to be coinci- 
dental rather than causal. See pages 179 to 
180, 182 to 183, and 194 to 195 for de- 
scription of the behaviors of subordinate rats 
which tend to elicit attack. 
C. Shelter Storage. The simplest behavior of rats 
with regard to food is to consume it at its source. 
The next increase in complexity is to transport the 
food a short distance before eating it. This 
slightly more complex behavior arises from the 
tendency of rats to seek shelter, which provides 
protection both above and to the sides. At each 
of the entrances of the Food Pen there was a metal 
tunnel which housed the photoelectric cell and the 
mechanism for recording the passages of the rats. 
This type of shelter was probably utilized by all of 
the rats for eating food they had transported from 
the center of the barren Food Pen. Although I 
have no quantitative data on this point, it is my 
general impression that as great a quantity of food 
was actually consumed in these four recorder 
102 
