252 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1936 



cated by crises that evict birds from some habitats and crowd them 

 into others or drive starving remnants from one place to another, 

 the cycle of mortality starts over again; and the birds continue to 

 be preyed upon largely in proportion to their vulnerability, if not 

 by horned owls, then by something else. 



Thus may be concluded this resume of the relationship of one 

 predator to one prey species as it has been worked out in one region 

 over a period of years. It does not necessarily typify predator-prey 

 relationships, though some others seem to be similar. Other relation- 

 ships are apparently quite different; still others consistently defy 

 scientifically acceptable analysis ; and, of countless others, it can only 

 be said that virtually nothing is really known of them. 



This writing is not intended to be a brief against all attempts to 

 control predators for economic or conservation or other legitimate 

 purposes. It does not imply that no control of any predators is 

 desirable in the conservation of the bobwhite, nor that control of 

 horned owls may not be important in the protection of species other 

 than bobwhite, nor even that under some conditions bobwhite con- 

 servation may not be aided by the control of horned owls. 



It does submit that predator control is frequently emphasized be- 

 yond any existing justification. Too often the persecution of pred- 

 ators — however futile — is the one thing that is stressed in the name 

 of conservation, whereas measures of the utmost merit are barely 

 toyed with, if not disregarded altogether. When predator control 

 is only blind, ruthless suppression of any and all flesh-eaters, or 

 alleged flesh-eaters, with no heed for the status of rare or endangered 

 species, it surely ceases to be the public interest and should be dis- 

 couraged the same as any other wasteful practice. 



The interrelationships of predation are exceedingly complex and 

 variable, and how much they will ever be understood is problem- 

 atical. The accumulating evidence seems to suggest that many 

 prey populations are constituted to withstand far more pressure from 

 enemies than they ordinarily get; and, within the restrictions im- 

 posed by their habitats, seem to be mainly self-limiting and self- 

 adjusting in numbers. The impacts of predation, then, are absorbed 

 by at least some populations that seem to be resilient chiefly accord- 

 ing to their needs. The trimming down by predation of excess 

 populations that must disappear, anyway, is incidental. It should 

 not be regarded as a threat to the permanent nucleus, which, barring 

 drastic change in environment, will continue to occupy all livable 

 quarters and produce the usual annual surplus. The surplus is 

 strictly temporary, and generation after generation is frittered away. 

 Whether taken by predators or otherwise lost, the surplus must 

 disappear; population sooner or later coincides with carrying 

 capacity. 



