AREA II 
time each utilizes either a single place of harborage 
or a few neighboring ones. From such centers of 
orientation the activities of the rats radiate in all 
directions. Some directions are favored over others 
because of the location of goals, such as sources of 
food. The general impression was obtained that 
there was a gradual decrease in the frequency of 
longer travels. However, it was impossible to 
obtain direct evidence of this. On the assumption 
that the outward travel from any point of orienta- 
tion follows the same general principle, an ap- 
proximation may be obtained by examining the 
distribution of feces adjacent to the outer limiting 
barrier fence. Rats passing outward through 
Passages 1, 2, 3, and 4 through the median barrier 
fence frequently traveled directly out to the outer 
limiting barrier fence and thence along it for 
varying distances toward a corner of the pen. 
Usually each rat would stop at some intermediate 
point prior to reaching the corner. When the rat 
again initiated travel, it would generally travel out 
into the area rather than continuing along the 
fence toward the corner. It is presumed that 
defecation occurred at these times when the rats 
stopped, since in the other regions of the pen the 
distribution of feces was such as to suggest that they 
were deposited at those points where the rats came 
at least to a momentary stop in their travel. 
Surveys on six dates gave a total of 4,793 feces 
along the outer fence. The fence was arbitrarily 
divided into five intervals of 10 feet each from the 
point opposite the passage through the median 
barrier fence to the corner of the pen (see fig. 74). 
The number of feces in these five intervals was: 
1,868, 975, 738, 545, and 667. The increase in 
the feces in the terminal group toward the corners 
of the pen presumably represents in part the feces 
that would have been deposited at points still 
farther away had the fence not terminated the 
outward travel. To the extent that the number 
of feces at any point were proportional to the 
number of trips taken to that point, conclusions 
can be drawn as to the utilization of space radiat- 
ing out from a point of orientation. The number of 
feces within any one 10-foot interval along the 
fence only partially reflects the extent of use of that 
area. This is because the number of trips through 
this region will be proportional to the sum of all 
the feces in that region plus the total feces in 
regions farther along the fence, since rats normally 
passed through the nearer regions along the fence 
in order to get to the more distant ones. Therefore, 
Figure 74 . — Some indications of space utilization and orien- 
tation by the Norway rat. The "fecal deposition fence 
positions" are in terms of distance along the peripheral 
fence directly opposite the passages through the median 
barrier fence (see fig. 75 ). The isobars of space utilization 
about the North and South Alley Burrows were prepared 
under the assumption that the probability (table 8) of 
rats being at different distances from the centers of the 
burrows follows the same pattern of decrement with 
distance as revealed by the deposition of feces along 
the peripheral barrier fence. On the average there was 
a circular flow of movement from the burrows, into the 
Food Pen, and back again. This flow reduced the number 
of contacts of rats proceeding in opposite directions. 
Harborage boxes are lettered with reference to increasing 
distance from the passages through the median barrier 
fence. See table 18 for details of utilization of these 
boxes. 
the accumulated totals of feces (4,793, 2,925, 1,950, 
1,212, 667) for the successively more distant 
locations along the fence were utilized as a more 
accurate reflection of the frequency with which 
rats pass through points at successively greater 
distances from a point of orientation. Both the 
actual and the accumulated totals of feces at the 
five fence positions are shown in figure 75. 
Although these accumulated totals of feces reflect 
the relative frequency of arriving at distances from 
a point of orientation, they do not reflect the in- 
tensity of usage of the environment. This arises 
from the fact that each band of equal width, w, 
about a point of orientation increase in area by 
and amount 2ttW 2 over the preceding band. Thus, 
as the amount of area in a band increases, the 
frequency of visitation to the band decreases. 
83 
