28 ANIMAL ECOLOGY 



animal which quietly replaces it without ever becoming *' red 

 in tooth and claw " at all ? Succession brings the ecologist 

 face to face with the whole problem of competition among 

 animals, a problem which does not puzzle most people because 

 they seldom if ever think out its implications at all carefully. 

 At the present time it is well known that the American grey 

 squirrel is replacing the native red squirrel in various parts of 

 England, but it is entirely unknown why this is occurring, 

 and no good explanation seems to exist. And yet, more is 

 known about squirrels than about most other animals. In 

 ecological succession among animals there are thousands of 

 similar cases cropping up, practically all of which are as 

 little accounted for as that of the squirrels. There is plenty 

 of work to do in ecology. 



14. It is probable that accurate data about the succession 

 in animal communities will be most easily and successfully 

 obtained by taking very small and limited communities living 

 in peculiar habitats, for it is here that the number of species 

 is reduced to reasonable proportions. Experience has shown 

 that the general study of animal communities is best carried 

 out on simple communities such as those of Arctic regions or 

 of brackish water. Habitats in which succession can be studied 

 quickly and conveniently are the dead bodies of animals, the 

 dead bodies of plants {e.g. logs, or fungi), the dung of mammals, 

 marine timber, temporary pools, and so on. The ecologist 

 will be able to find a number of such habitats wherever he is ; 

 and they all contain on a small scale similar communities to 

 those found in woods or lakes. In such places succession is 

 always in progress and, what is more important, in quick 

 progress. The writer has found that it is almost impossible 

 to make even a superficial study of succession in any large 

 and complicated community, owing to the appaUing amount of 

 mere collecting which is required, and the trouble of getting 

 the collected material identified. When one has to include 

 seasonal changes throughout the year as well, the work becomes 

 first of all disheartening, then terrific, and finally impossible. 

 Much of this mental strain can be avoided by choosing simple 

 communities, and the results as contributions to the general 



