NORTH ALLEY BURROW WITH ITS EXTENSION 
TOWARD PASSAGE 4 ON JUNE I, 1949 
i i i I i I I I I I I I I I I I I I I L I 1 1 1 1 I I I I I I I I I I I 
O 10 20 30 
FEET 
Figure 22. — The pattern of tunnel systems developed at the North Alley Burrow. Once the tunnels contacted the fence they 
followed close to it with few interconnections. The decay of the older section of the burrow is associated with its inhabit- 
ance by socially low ranking rats, which exhibit an inhibition of the behaviors involved in the development and maintenance 
of tunnels and nests. 
BURROW STUDY / / 
2 [MOUND/ 
SCALE IN FEET 
Figure 23. — Patterns of burrow systems during the early stages of their development. Also see figure 34. 
676-768 0—63 3 
25 
