172 AGGREGATION, COMPETITION AND CYCLES 



in all directions, so that independent ranges were out of the question 

 in these species. However, in general, -territories and runways are 

 usually distinct and nests spaced well apart. 



BIOTIC BALANCE 



The older naturalists expressed the untenable view that a stable, 

 static equilibrium existed among the organisms of any community, 

 and in nature in general. It was further thought that fluctuations in 

 populations of insects pests and other small forms were due to biotic 

 modification by agricultural practices. This appears to have been 

 assumed (Forbes, 1880, a, and others) in the face of locust outbreaks 

 in the undisturbed western grassland to the contrary. Forbes says: 

 "There is a general consent that primeval nature, as in the uninhabited 

 forest or the unfilled plain, presents a settled harmony of interaction 

 among organic groups which is in strong contrast with the many seri- 

 ous maladjustments of plants and animals found in countries occupied 

 by man." 



In regard to the larger animals whose life histories and life spans 

 are long and whose rate of replacement is slow as compared with the 

 rapidly reproducing rodents and invertebrates, there is some evidence 

 for distortion of equilibrium as regards numbers. Disturbance of bal- 

 ance in the deciduous forest is suggested in a diagram by Wood (1910) , 

 which is reproduced in Fig. 20, showing an increase of deer accom- 

 panying the decline of predators. The fact that prairie dogs increased 

 with the reduction of wolves and coyotes (INIerriam, 1901) is further 

 evidence of some kind of a balance among the larger forms. Increase 

 of deer to a point endangering their food supply has occurred repeat- 

 edly in recent years under protection and the reduction in numbers of 

 predators. Such facts, so far as experience had brought them to atten- 

 tion a half century ago, were perhaps responsible for the idea of a 

 stable equilibrium in regions not affected by man. 



A natural result of this view has been so much tampering with 

 communities in the name of agriculture, game conservation, and the 

 preservation of rare species that it has been difficult to ascertain what 

 the normal fluctuations are. Custodians of parks, forests and game 

 preserves have usually viewed all declines of popular animals and all 

 increases in unpopular ones with alarm, and immediately proposed 

 and often executed useless or detrimental remedial measures. 



The difficulty has arisen from the fact that normal fluctuations 

 in abundance in areas not influenced by man had been but little 

 studied. However, in the past decade, investigations have brought 



