1. The Social Use of Space 139 



Where fx = Ho and N = No it may be seen by substituting Eq. (80) into 

 Eq. i'-U) that the frequency of contacts will remain constant at (Nb — 1) 

 regardless of the increase in density. Since we are considering the special 

 case where area, A, remains constant, the constancy in the absolute num- 

 ber of contacts despite increases in density can only derive from decreases 

 in the d or the v component of ju = dv/A. 



Where decreases in ju transpire within the lifetime of an individual as an 

 adjustive change to increase in density, and where this decrease in m results 

 solely from a decrease in the target diameter, d, this change must be re- 

 flected through reductions in the frequency of usage of signahng mechanisms 

 or of the intensity of such signals. Vocalizations should occur less frequently, 

 be less complex, and of reduced intensity. Bodily display characteristics 

 under voluntary control should similarly be reduced, as should also the 

 use of chemical signals. Similarly, when a species, A, now exhibits an Nb 

 of 80-120 or 800-1400 (see Section XIII, B, 3) but there is reason to sus- 

 pect that at some earlier era it had had an Nb of 2 or 12, such as is still 

 expressed by a related species (or genus), B, then a comparative examina- 

 tion of species of types A and B should reveal that members of species B 

 more frequently resort to the utilization of vocal, display, and chemical 

 signals and that these are of greater complexity and intensity than in 

 species A. In making any such comparisons it is well to keep in mind the 

 earlier hypothesis that the change of an Nb = 2 to an Nb = 12 may lead 

 to an increase in complexity of the signal. For this reason, it is more ap- 

 propriate to compare a species w^hose A^6 has a typical range of 7-19 with 

 one which rarely falls below 80. Such comparisons will provide critical 

 tests of the general formulation. 



In like fashion, velocity, v, may be the factor which becomes reduced as 

 density increases. This reduction may be expressed in any of the three 

 aspects of v listed in Section XIII, A, 1. Sense organs may become less 

 effective with reference to the animals' perception. This reduces ^i. Such 

 a tactic must be effective only through genetic changes and so can serve 

 only as a long-term adaptive mechanism. The animal may also reduce its 

 V2 by w^ay of reducing the number of trips it makes, or by altering the time 

 and place of its activities. This strategy includes initiating activity while 

 others are resting, or by becoming cryptic in the sense of becoming arboreal 

 or subterranean. Finally, the animal may reduce its Vs, its actual rate of 

 movement. 



Although such reductions in d and v will lead to a reduction in m which 

 will compensate for increase in density, it is obvious that n must decline 

 so markedly as to present biological limits of effectiveness. Further accom- 

 modation to increases in density must require m' to decrease also. Reduc- 

 tion in this communication-inhibiting or contact-blinding factor means 

 (a) decreased duration or intensity of behaviors or decreased memory 



