68 John B. Calhoun 



other. At such times whichever one became more numerous than the other 

 would cause members of the less numerous species to contract their home 

 ranges and live within the interconstellation matrix of the more abundant 

 species. 



A small amount of trapping during 1946-1948 revealed that Peromyscus 

 still held a 3:1 relative abundance over Cleihrionomijs. The intensive trap- 

 ping was resumed during 1951, an apparently critical year in the social 

 balance of the population. Forty-one NACSM traplines, each run for three 

 consecutive days, for a total of 7380 trap-nights of effort (NACSM Re- 

 lease No. 5) provided total catches for the three consecutive days as 

 follows: Clethrionomys: 143, 114, 77; Peromyscus: 167, 132, 108; Blarina: 

 52, 58, 50; Sorex: 2, 0, 2. Although Peromyscus was slightly more numerous 

 than Clethrionomys, 9.93 versus 8.15 per trapline per three days, its slower 

 rate of decline in captures from days 1 through 3 suggests that it was 

 slightly subordinate and that some of its members were enlarging home 

 ranges as their associates were being trapped off. However, the nearly 

 constant total catch per day for Blarina clearly indicated its subordinate 

 status to the other two genera. 



The 24-day continuous removal study of 1951 (Table V, Fig. 12) pro- 

 vided further insight into this realignment of social relations. Despite 

 nearly equal numbers taken for the three most abundant species, Blarina 

 is clearly subordinate to both Peromyscus and Clethrionomys. Its more 

 marked contraction of home ranges is revealed by the continuously in- 

 creasing daily catch over the first few days of trapping (Fig. 12) . Compari- 

 son of the proportion taken the first 5 days with that during the last 5 

 days provides an index of expansion of home range. The relatively more 

 that are taken during the first 5 days, the less has been the expansion of 

 home range, and thus the more dominant the species. On this basis, the 

 four genera are listed in order of decreasing rank in Table V. 



One of the most remarkable aspects of this set of data is the nearly con- 

 stant daily catch for each of the three more abundant genera between the 

 4th and 17th day of trapping. This means that within each genus, survivors 

 increase their home range each day sufficiently to result in as many en- 

 countering traps as on the previous day despite their fewer numbers. 

 Furthermore, an individual member of each of these genera must be re- 

 ceptive to the inhibitory signals from the other two genera as well as of 

 others of its own kind. Otherwise, the capture curves would have resembled 

 that for clearly alpha species (Fig. 9). 



This set of data also suggests that in the presence of several more domi- 

 nant species actively contending for rank status, the very subordinate 

 Sorex not only is markedly reduced in numbers, but also is much slower in 

 expanding its home ranges. Peak captures, and thus maximum expansion 



