Figure 41. — Surface of the South Alley Burrow during April 1949. The sealed hole 18 is in the center of the circular area 
of bare dirt in the extreme right center. Path 1 crosses the foreground. Hole 31 is in the center of path 1 . See figures 20 
and 21 for other features. Also compare the appearance of this burrow with its state a year previously as seen in figure 4. 
Photograph by U.S. Army Signal Corps. 
Table 3. — Number of burrow sealings related to number 
of young weaned 
South Alley 
and Area I 
North Alley 
and Area III 
Number of burrow sealings . . . 
15 
46 
Number of young weaned 
during 1 947 and 1 948 
107 
62 
Considering this evidence I think that it is fair to 
assume that the incidence of this burrow sealing 
behavior is in some way dependent upon the char- 
acter of the social structure of the group. It is 
more likely to occur in groups with an unstable 
composition of members and in which the mem- 
bers are rather low ranking with regard to the 
hierarchial structure of the whole society. The 
676-768 0 - 63-4 
exact dependency relationship between this behav- 
ior and social rank is rather problematical. There 
are at least two possible causes: (1) The presence 
of a burrow seal may make it less likely that a more 
dominant rat will enter the harborage of a socially 
low ranking rat. (2) The burrows of rats having 
lower social rank exhibit a higher “catabolism”, 
with which is associated more breaks in the burrow 
system which allow light or air leaks. Thus, the 
increased incidence of the burrow sealings may only 
relate to the greater frequency of breaks in the 
structure of the burrow system. See the previous 
discussion of the histories of the North and South 
Alley Burrows (pp. 15-20). 
There are two behaviors closely associated with 
this burrow sealing. Each was observed only 
twice. One of the ways in which rats seal openings 
into their burrows is with wads of mud which they 
41 
