1. The Social Use of Space 



83 



placed, one at approximately every .5 feet. Along two diameters at right 

 angles to each other, 156 additional traps were placed, 3 to a station and 

 with a 50-foot interval between stations. This central cross of traps was 

 intended to facilitate removal of residents and afterward capture any in- 

 vaders "filtering" through the peripheral circular trapline. All 937 traps 

 were run for 80 consecutive days. Xo Clethrionomys entered the traps on 

 the 21st day. Prior to that, 101 were caught and, in addition, six died in a 

 preceding period of live trapping. These 107 individuals presumably 

 represent the majority of residents. Between the 21st and 80th day of 

 trapping, 501 additional redbacks entered traps. Furthermore, these 501 

 represented four fairly definite waves, roughly 15 days elapsing between 

 the beginning of each wave and the start of the next one. Each later wave 

 exceeded in numbers that of the preceding one (Fig. 31). 



Let us now return to a consideration of the hypothesis, originally con- 

 ceived from reflecting upon the results of Hinckley's 1950 Maine study. 

 Although it is now recognized that the hypothesis does not apply to the 

 study from which it originated, w^e shall now ask the question: "Does it 



140 



UJ 



O 130 



o 



21-35 36-50 51-65 66-80 



PERIOD OF CAPTURE (DAYS) 



Fig. 31. Invasion of redbacked mice into an area from which most of the residents 

 had presumably been removed. 



