1. The Social Use of Space 67 



of their own kind. Yet even with them their movements are sufficiently 

 inhibited as to reduce contacts far below that otherwise possible. How- 

 ever, with Peromyscus so much overlapping of home ranges existed that 

 most individuals must have had frequent associations with others of their 

 own kind. Reduction of communication with others of their own kind ac- 

 companies interspecific social subordination. The lower the rank of a 

 species, in terms of the degree other species in the community cause it to 

 restrict its home range, the more its intraspecific systems of communication 

 will be reduced. Even, as the analyses shown in Figs. 28-30 suggest, if 

 there develops some compensatory clumping of home ranges by members 

 of subordinate species, there must still be a greater degree of isolation 

 between such clumps than between any comparable number of groups of 

 the dominant species. 



F. The Instability of Social Relations 



Results from the extensive censusing of small mammals conducted by 

 Drs. Patric and Webb and their associates at the Huntington Forest form 

 a major key in unraveling the process involved in community structure. 

 Fortunately, their records (Patric, 1958) include some of the years before 

 1952 (see Table VI for 1952-1956) . 



An effort of 9650 trap-nights during 1940 and 1941, in which traps were 

 set for five consecutive nights, caught 173 Clethrionomys and 1280 Peromys- 

 cus, or 7.4 Peromyscus for each Clethrionomys; in contrast, during the 

 years of 1952-1956, 4.1 Clethrionomys were captured for each Peromyscus 

 taken (Table VI). However, during these two years the trends of capture 

 over time were so nearly identical that only the greater numbers of Pero- 

 myscus can argue for its having been more dominant. Actually, both 

 showed increases in catch per day as associates were removed. The day 1 

 to day 5 captures were: for Peromyscus, 117, 225, 313, 317, 308; for Clethri- 

 onomys, 17, 19, 61, 46, 30. Apparently many members of both species were 

 characterized by reduced home ranges, which they expanded as associates 

 were removed. There being so few Clethrionomys present, they could not 

 represent the species producing the inhibition of home ranges. Thus at this 

 time we must suspect that actions by members of the genus Peromyscus 

 not only caused many of its own kind to contract their home ranges, but 

 also caused similar contraction by Clethrionomys. In the light of the ap- 

 parent reversibility of social roles of these two genera, previously discussed 

 when comparing different localities, these comparisons between different 

 eras within the same habitat suggest that Peromyscus and Clethrionomys 

 in this habitat are really codominants, but that one will nearly exclude the 



