THE PHENOMENON OF PREDATION — ERRINGTON 513 



appear, broadly, not too dissimilar. Parts of grasshopper popula- 

 tions may, as for the muskrats, be relatively well situated ; other parts, 

 crowded into inferior habitats or beset by the frictions of overpopula- 

 tions, are more exposed to miscellaneous mortality factors, including 

 predation. 



I can now see that a good deal of the predation suffered by grass- 

 hoppers — which I had long assmned to be more random, more of a 

 gradual-attrition type — falls instead in more of an off-and-on, secure- 

 and-insecure dichotomy. 



(I am reminded that once I had even felt that the predation borne 

 by an abmidant muskrat population was proportional to the numbers 

 of muskrats and the predators preying upon them, whittling down the 

 general muskrat population little by little. That was before any 

 attempts were made to inquire more deeply into what was happening. 

 With careful local analyses, it became apparent that the predation 

 that suggested gradual attrition was not in fact working that way 

 on the muskrat population as a whole ; it was conforming to the same 

 overall rules of order that the Iowa muskrat studies had been bringing 

 out again and again, whereby parts of the population lived very vul- 

 nerably while other parts retained their security.) 



When reexamining questions of social intolerances and population 

 effects of predation in the Animal Kingdom, I do not feel surprised 

 because of the fewness of pat answers that come to mind. 



Predator-prey relationships are hardly likely to be unaffected by 

 social frictions, established property rights, and complex behavior 

 patterns just because the participants happen to be classed as lizards, 

 fishes, insects, and crustaceans instead of as mammals and birds. Nor 

 should the greater collective fecundity of lower vertebrates, with 

 corresponding individual cheapness of life, be considered a complete 

 explanation for the lesser territoriality of lower vertebrates. Even 

 among higher vertebrates, the strongly territorial gray wolf with 

 close family ties has, on paper, a far higher biotic potential than its 

 prey, the deer and caribou that may congregate in tremendous num- 

 bers. Nor can the lesser territoriality of lower vertebates be wholly 

 explained in terms of their lesser intelligence and lesser adaptiveness, 

 for territoriality reaches some of its most pronounced evolutionary 

 peaks in birds, which as a class are less intelligent and adaptable than 

 are mammals as a class. 



The point is, once more, that Life selects for what works out, ir- 

 respective of our human efforts to define and classify. 



INTERCOMPENSATIONS 



We may next consider something else that Life selects for, something 

 that is very often interlinked with or a byproduct of territoriality. 

 It is a tendency to compensate, one of the prime upsetters of both 



