1. The Social Use of Space 27 



slowly. It began in 1950 when I asked A. Dexter Hinckley, then a summer 

 student at the Jackson Memorial Laboratory, to continue eight NACSM 

 lines for 15 days (see Section VI, E and Fig. 13A). Despite the expectation 

 of a continually declining catch after the first 3 days, it turned out that the 

 number taken from day 4 onward actually increased each successive day 

 until on day 15 three times as many individuals entered traps as did on 

 day 1. 



These results initiated an intensive effort to explore the results obtained 

 from prolonging the period of removal trapping. I am particularly indebted 

 to Drs. William L. Webb and Earl F. Patric of the Huntington Wildlife 

 Forest, and to my colleague. Dr. Kyle R. Barbehenn. Without their per- 

 mission to utilize here some of the data from their extensive studies of 

 removal trapping, it would have been impossible to develop the concepts 

 elaborated in succeeding sections of this paper. I have also profited from 

 a number of 30-day census contributed by other NACS]\I cooperators. 



Our concern here will be with the contribution of this program, and 

 allied research developing from it, to furthering our understanding of 

 home range and the organization of small mammal communities. The 

 following few sections merely present results. Note that within each study 

 presented, the several species present markedly different patterns of cap- 

 tm*e by traps over time. Interpretations based upon the data in Section 

 VI are given in Sections VIII, IX, and X. 



A. Rich Lake Island, New York, 1952, Sixty-Day Removal Study— Data 

 Contributed by William L, Webb' 



Four NACSM traplines were run on this island in the Huntington 

 Forest for 60 consecutive days, beginning August 16. The red-backed 

 mouse, Clethrionomys, and the shrew Sorex formed the majority of the 

 catch. Figure 9 gives the results for the first 30 days. Note that 

 Clethrionomys, which entered the traps in large numbers during the first 

 few days, was by the end of 30 days represented by only half the total 

 catch as that for Sorex, Avhose peak in catch per day did not come until 

 the ninth day. Both species exhibited a secondary minor period of increase 

 in captures. 



During the same summer, 34 NACSM lines were run for the standard 

 3-day period in similar forests on the mainland (Table IV). As on the 

 island, comparatively few Sorex entered traps on mainland areas during 

 the first 3 days of trapping. And yet, continuous removal trapping for an 

 80-day period (Section XI) in one tract of the mainland forest produced 

 ()17 Clethrionomys and 1225 Sorex. 



