RELATIVE FREQUENCY OF TYPES OF TUNNEL SEGMENTS 
Figure 49. — Relative frequency of types of tunnel segments in relation to the size of a burrow. The number of tunnel seg- 
ments per burrow is listed on the abscissa. This figure is based on the classification of 712 tunnel segments from 44 
burrows. 
individual inhabits only a portion of the burrow 
it is possible for it to experience, and presumably 
conceptualize, the situation of alternate or multiple 
routes of travel between goals. Rats living within 
the elongate burrow have relatively fewer oppor- 
tunities for experiencing alternate routes of travel 
to goals and thus may develop a more sterotyped, 
less complex conceptualization of possible modes 
of action. It is suspected that such differences in 
conceptualization of the complexities of the physical 
environment have reverberations on the ability of 
the individual to develop complex social interre- 
lationships. 
In fact the hypothesis is forwarded that there 
are mutual cause and effect interrelationships 
between social integration and burrow integration. 
The effect of social integration upon the mainte- 
nance of burrow integration is reflected in the 
histories of the South Alley Burrow (fig. 21) and 
the North Alley Burrow (fig. 22). As will be 
documented later (p. 204) the greater social 
integration of the inhabitants of the South Alley 
Burrow is reflected in (a) a higher reproductive 
rate, (b) fewer males per female, (c) higher rank 
in the social hierarchy by its members, and (d) 
more rapid growth rate of the individual members. 
These two burrows — and their contained colonies — 
have histories of identical duration in time. When 
the study was terminated in May 1949, the rats in 
the South Alley Burrow had maintained the 
older section of the burrow system in fair repair 
and in direct connection with most of the newer 
sections. By this time the rats of the North Alley 
Burrow had allowed the older sections to become 
50 
