52 John B. Calhoun 



ten, no matter where it is in its home range. Since the dynamics of the use 

 of space relating to uniformity of utihzation of resources and the character- 

 istics of the sign and signal field all point to an optimum interval between 

 home range centers of somewhere near 2 sigma, it follows that there should 

 have been evolutionary adjustment of tolerance to simultaneous or near 

 simultaneous communication with five to ten others. 



VIII. Interpretations of Observed Data Derived from Removal Trapping of 



Small Mammals 



At this stage in the development of a concept of community organiza- 

 tion, one must resort to a certain amount of quasi circular reasoning. 

 Regularities in observed results lead to theoretical formulations. Then these 

 formulations can be used to reexamine the data for further insight. This is 

 my present intent. In time, many aspects of the concept may be subjected 

 to more rigorous study. However, for the present we must content ourselves 

 with a search for a best approximation to a very complex set of phenomena. 



Section VI, "Continuous Removal Trapping of Small Mammals," 

 presented results from several extensive studies. Specific interpretations 

 follow\ 



A. The Relationship between Two Dominant Species 



The dominant species in the community reveals itself during removal 

 trapping through its members having such large home ranges that every 

 individual living near a trap has a high probability of encountering it. 

 Thus, for them, few^r days lapse from initiation of trapping until 50% of 

 the population is caught. As can be seen from the two Alaryland studies 

 presented (Fig. 10 and Fig. 13B), Peromyscus fulfills this criterion. For 

 species associated with Peromyscus, whether they be Blarina and Sorex, or 

 Blarina and Pitymys, the dates of 509(' removal arrive much later. The 

 later the date of 50% removal, the more subordinate a species, and the 

 more slowly its members expand their home ranges as the dominant 

 species is removed. 



In more northern forest habitats, Peromyscus rarely is found in the 

 absence of Clethrionomys. In fact, it is as if the red-backed mouse is just 

 superimposed upon the simpler Peromyscus-Blarina- Sorex community of 

 more southern forests. Typical dominance of Clethrionomys over Peromyscus 

 may be seen in Figs. 9, 11, and 13A. Although I am convinced that 

 Clethrionomys usually can develop the ability to inhibit the home range of 



