Figure 57. — Aggregation of rats in box 30 on December 22, 1948. In addition to the 14 seen here there were 9 others in 
this aggregate which were crowded into a burrow nest cavity (see fig. 33) immediately adjoining the box at the lower 
right. The unbalanced sex ratio of 1 7 males to 6 females was one indication of the low social rank of this large 
aggregate. 
basic pattern of the trailway system was apparent. 
This pattern was one of trails connecting basic 
goals. One harborage is connected with an adja- 
cent one; harborages are connected with sources 
of food; and had there been alternate sources of 
food, as is usually the case with natural populations, 
trails would have connected them. 
The trails are normally just wide enough for a 
single adult individual to travel. Frequently, two 
individuals pass without showing antagonism. 
In such cases each appears to step slightly aside. 
The frequency of this event is probably not great 
enough to cause much widening of the trail. 
Unfortunately, a series of measurements of the 
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