IN UMBERS: DYNAMICS 61 



statistics av.ailable through the fur- trade. The 

 earher work of animal ecologists showed Uttle reaUza- 

 tion of the importance of animal numbers, and animal 

 ecology is now going through a stage in which it is 

 being loaded with tremendous economic problems 

 connected with the numbers of fishes and rodents 

 and insects and other animals, while the purely 

 scientific aspects of that subject are the least fully 

 developed. We may therefore look forward to a 

 period during which the studies of ecologists them- 

 selves will be greatly supplemented by material 

 gathered for economic reasons and also by other 

 material suppUed by the labours of naturalists, who 

 are in process of transferring to census work (collecting 

 facts about the numbers of wild animals) much of 

 the energy which they formerly appHed (most use- 

 fully also) to the collection of specimens for study 

 by systematists. 



One of the most important generalizations that 

 can be made about wild animal populations is that 

 they fluctuate greatly in numbers. Naturalists of 

 the nineteenth century took over without alteration 

 the idea of the balance of life, i.e. constant popula- 

 tions. The earlier religious ideas had included the 

 concept that the world was created in an orderly 

 way, and disturbances in this order were attributed 

 either to the acts of man himself or to the acts of 

 God in punishing man for his presumption in up- 

 setting this order, or perhaps in doing anything new 

 at all. This general concept fitted naturally into 

 the later biological theories of adaptation among 

 animals, since it was supposed (rightly) that animals 

 were closely adapted to their surroundings and 

 (wrongly) that this adaptedness would lead to a 

 state of steady balance between the numbers of 

 different species. Whatever the various theories of 

 adaptation may be found to require we are now in 

 a position to show that wild animals do fluctuate 

 very much and that these fluctuations are not simply 



