516 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 64 



We may go on from quail and pheasants and muskrats and see simi- 

 lar evidences of social interplays and compensations in the extensive 

 literature on population dynamics. Poison-depleted rat and ground- 

 squirrel populations have responded to lessened social tensions by ac- 

 celerated rates of increase. The red fox, despite sport and bounty 

 hunting in north-central United States, not only maintains its numbers 

 at high levels in suitable range but also, I should say, thrives with 

 heavy hunting mortality. Heavily hunted deer populations produce 

 greater numbers of twin fawns than the less hunted. Mallard ducks, 

 though overshot by man, have remarkably low "natural" loss rates 

 compared to blue-winged teal, which are relatively little subject to 

 human hunting. Heavily exploited stocks of sport or food fishes have 

 faster growing individuals than less exploited stocks in the same 

 waters. The Iowa lake that most consistently produces the greatest 

 numbers of large bullheads of which I know is at the same time among 

 the most heavily fished. 



Of course, one could easily overgeneralize. I am aware that many 

 species of birds have practically no renesting in them. Some grouse 

 may normally make but a feeble attempt at renesting and then only 

 if their initial clutches of eggs for the season be destroyed before the 

 laying birds have invested much time in incubation. The shortness 

 of the summer does not leave Arctic-nesting waterfowl much time for 

 renesting, at best, if the late-hatched young are to develop enough to 

 fly out before freeze-up. Even the bobwhite quail may lose its renest- 

 ing resilience under the influence of severe and prolonged drought. 

 There are conditions under which the most resilient of species will not 

 try to breed at all, under which there seems to be no chance for any 

 kind of compensatory balancing, at any stage of life. 



As concerns either the lack or the prevalence of intercompensatory 

 trends in the population dynamics of invertebrates, I feel too unsure of 

 myself to generalize. I do not have to go far in this direction soon to 

 find myself outside of my radius of professional experience. Of the 

 opinions about compensations expressed in the invertebrate literature, 

 a great deal remains inconclusive. Many leading students of popula- 

 tion dynamics of insects regard compensatory tendencies as of general 

 application throughout the Animal Kingdom ; another very respected 

 entomologist regards compensatory predation as probably uncommon 

 in insects. 



Perhaps, it may be argued that, concerning phenomena in which 

 almost anything can happen, everyone can make whatever choice 

 pleases him, but I do not think that that is a scientifically fair judgment 

 to make. In studies of the exploiters and the exploited, we deal with 

 adaptations of long standing. We need not restrict ourselves to the 

 Animal Kingdom to see this. Grass grows anew in response to graz- 



