190 ANIMAL ECOLOGY 



naturally into a series of ecological phases : preliminary survey, 

 factors (biotic and otherwise), animal communities, numbers, 

 regulation of numbers, dispersal, and (if so inclined) origin of 

 species. 



Human ecology and animal ecology have developed in 

 curious contrast to one another. Human ecology has been 

 concerned almost entirely with biotic factors, with the effects 

 of man upon man, disregarding often enough the other animals 

 amongst which we live. Owing to the fact that most of the 

 workers in this subject are themselves biotic factors, an undue 

 prominence has been given in history and economics to these 

 purely human influences. It is only recently, under the 

 influence of men like Huntington ^^^ and Hill,^"^^ that the 

 importance of physical and climatic factors in man's environ- 

 ment has become recognised. In animal ecology it has been 

 entirely the other way about. Attention has been concentrated 

 on the physical and chemical factors affecting animals, and if the 

 biotic factors of vegetation and other animals have been studied, 

 they have played quite a minor part in ecological work, or have 

 been studied from the point of view of evolution, either to 

 prove or to disprove the powers of natural selection in producing 

 adaptations. As a matter of fact, we are now in a position to 

 see that animals live lives which are socially in many ways 

 comparable with the community-life of mankind, and if these 

 resemblances be only considered as analogies, there yet remains 

 the important fact that animal communities are very compli- 

 cated and subject to regular rules, and that it is impossible 

 to treat any one species as if it were an isolated unit, when 

 we are studying its distribution and numbers. 



I am ending this book with a diagram which attempts to 

 illustrate in a rough way the relation of the various branches 

 of ecology to each other, and to other branches of science. 

 The diagram is based upon the order of the chapters in this 

 book ; and it may serve as a reminder that ecology is quite 

 a large subject. 



