38 John B. Calhoun 



longer present. In the absence of the inhibiting influences emanating from 

 the former alpha neighbors, the beta individuals then make a comple- 

 mentary expansion of their home range. As they do so, some beta individuals 

 come into contact with traps and are also removed. Inspection of a number 

 of continuous removal census in which there is an alpha species and one or 

 more subordinate species indicates that maximum expansion of home ranges 

 of the subordinate species is generally reached by the fifteenth day of 

 trapping. After this time, the catch by day for subordinate species also 

 declines over time since fewer and fewer remain to be caught. 



B. The Nature of the Inhibitory Influence 



Both Sorex and Blarina in Fig. 10 and Sorex in Fig. 9 exhibit an increase 

 in catch even beginning on the second day of removal trapping. Similar 

 results apply to the subordinate species included in Figs. 11-14, although 

 not so apparent in those graphs where the ordinate represents accumulated 

 catch. These results indicate that even removal of a small proportion of 

 the alpha species is sufficient to induce home range expansion by sub- 

 ordinate species. Thus, the means of communication through which in- 

 hibition operates must be sufficiently effective and repetitive that a change 

 in the general field intensity (or frequency) of stimuli emanating from an 

 alpha species is detected within a few hours at least by subordinate species. 



Bodily contact by random movement is unlikely to be effective. By the 

 same token that it takes several days before all alpha species are taken in 

 traps, it follows that in many instances subordinate species would be un- 

 aware of the absence of their alpha neighbors if this detection were a con- 

 sequence of a change in frequency of contact. Production and detection of 

 scent, at least where scent signposts are concerned, would likely operate 

 to inhibit home range expansion because of the persistence of scent beyond 

 the death of alpha individuals. Sight is unlikely to be an effectual means 

 of detection of alpha by beta species, both because of concentration of 

 activity during the night by many species and because many of these beta 

 species actuality spend considerable time under the leaf mold. 



There remains vocalization and audition as the means of communication. 

 Although there is as yet no proof that such is the means of communication 

 whereby individuals can detect the presence of unseen neighbors, it stands 

 out as the most likely possibility. iVIost small mammals do vocalize. 



Fewer barriers exist that might prevent or distort the passage of sound 

 through the environment than is true with regard to light stimuli or odors. 

 In the following discussions vocalization and audition will be assumed to 

 be the means of communication within and between species. However, 



