DISTRIBUTION OF FECES ALONG THE PERIPHERAL FENCE 
FENCE POSITIONS FROM OPPOSITE TILE PASSAGE TO 
CORNER OF PEN 
Figure 75. — Distribution of feces along the peripheral fence- 
From the point immediately opposite the passage through 
the median barrier fence, the 50-foot section of the 
peripheral fence was arbitrarily divided into 5 sections 
(fig. 74), and the number of feces in each was counted. 
Since rats normally defecate only after stopping, and 
after stopping along the peripheral fence they either 
returned along the previous route or moved out into the 
areas. The number of feces is probably proportional to 
the frequency of making trips of the distances at which the 
defecation occurred. The accumulated total of feces 
represents*an index of the probability of the rats passing 
through points with reference to the point of orientation, 
that is the passage through the median barrier fence. 
Therefore, the relative usage of a given amount 
of space will decrease much more rapidly than the 
frequency of making trips of successively longer 
lengths. This is shown in table 8. This extremely 
rapid rate of decrement in the intensity of space 
utilization by rats at points of increasing distances 
from a point of orientation indicates that there 
can be very little effective interaction between the 
organism and its environment very far from the 
center of orientation. 
If this table adequately reflects the intensity of 
utilization of space at increasing distances from 
the center of activity, certain inferences may be 
made regarding the manner in which different 
groups of rats interact in their utilization of space. 
Only two major burrow systems were constructed 
in the “Alley” about the Food Pen. The center 
of these two mature burrow systems with 10-foot 
isobars of space utilization about them are shown 
in figure 74. In the region where the isobars of 
these neighboring burrows systems overlap there 
will be an increase in the space utilization equiva- 
lent to the sum of the overlapping bands. This 
suggests that this increase in the relative intensity 
of space utilization might limit or modify the 
movements of rats irrespective of any social an- 
tagonism which might exist between adjacent 
colonies. 
Table 8. — Relative intensity of use of bands of 10-foot 
width from a point of orientation 
Band 
Distance 
to outer 
limit of 
band in ft. 
Area of 
band in 
sq. ft. 
Relative 
number 
of trips 
into band 1 
Relative 
visitations 
per 314 sq. 
ft. (i.e., equiv- 
alent area) 
A 
10 
314 
100. 0 
100. 00 
B 
20 
942 
61. 2 
20. 40 
C 
30 
1, 571 
37. 5 
7. 50 
D 
40 
2, 199 
22. 9 
3. 27 
E 
50 
2, 827 
14. 0 
1. 56 
F 
60 
3, 456 
8. 6 
.78 
1 The relative number of trips into a band was determined 
on the basis of the fact that the decrement in accumulated 
total of feces at each position along the fence decreased 
on the average of 38.8 percent from that of the previous 
position. 
Although this possibility was not recognized 
during the course of recording observations over 
the history of the pen, there were, nevertheless, 
accumulated certain observations which are rele- 
vant. These pertain to the 65 observations of 
known individuals, where the passage utilized 
to enter the Food Pen, as well as the passage used 
subsequently to depart from the Food Pen, was 
recorded. The number and direction of trips 
through each passage is shown in figure 74. It 
will be noted that for Passages 5, 7, and 8, the 
passages nearest the burrow systems, there are 
fewer exits than entrances. The deficit is made 
up through Passage 6 which leads into the East 
Alley. Here in the East Alley near Passage 6 the 
sum of the theoretical relative usage, as reflecting 
centrifugal movements in the absence of the food 
goal, would be 6.6 or less in contrast with ap- 
proximate relative usages of 9.1 for Passage 5; 
10.8 for Passage 7; and 15.0 for Passage 8. Thus, 
once rats were at the source of food their return 
journey home could be made with a greater 
avoidance of contacts with other rats, who were 
84 
