CHAPTER II 

 ECOLOGICAL SURVEYS 



ECOLOGICAL research sets out to define the 

 relations between animals and their surround- 

 ings. What are these surroundings ? They include 

 not only the climate and soil and vegetation, but 

 also the other species of animals that hve there. 

 The habitat of every animal is partly dead and partly 

 living, and environmental factors are therefore usually 

 classified by ecologists into edaphic and chmatic on 

 the one hand, and biotic on the other. In practice 

 the habitat can best be studied along three fines : 

 the physical and chemical factors, the vegetation, and 

 the animal community. It is not possible to obtain 

 a real picture of the fife of any species unless we bring 

 into this picture aU the other species of animals 

 associated with it. The nature of these associations — 

 involving food, enemies, parasites, competitors, etc. 

 — is discussed in Chapter III. Before such problems 

 can be discussed at all it is necessary to carry out 

 prefiminary ecological surveys which enable the 

 animal community of each habitat to be described 

 and defined. When we know that a species fives in 

 certain conditions of cfimate, on a certain soil, in 

 such and such a woodland type, in company with 

 several hundred other species whose names and 

 habits of life are known, and is itself inhabited by a 

 definite series of parasites, then the stage is set for 

 a discussion of the relation of the species to its 

 surroundings. 



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