DISTRIBUTION OF ANIMAL COMMUNITIES ii 



In America they are usually referred to as " life zones," and 

 the existence of great mountain ranges in that country is one 

 of the reasons why ecology has attracted more attention there. 

 In England, where the mountain ranges are in the north, we 

 do not see the impressive spectacle of great series of vegetation 

 zones which have so much attracted the American ecologist. 

 This vertical zonation is most striking in the tropics, where, 

 within the same day, one may be eating wild bananas at sea- 

 level and wild strawberries on the mountains. One of the 

 best descriptions of this phenomenon is given by A. R. Wallace 

 in the account of his travels through Java.^^ 



The work of botanists has given us fairly clear ideas about 

 the distribution of zones of vegetation, but we are still in great 

 ignorance as to the exact distribution and boundaries of the 

 animal communities in these Hfe zones, and of their relation 

 to the plants. A good deal of work has been done by Americans 

 upon certain groups of animals (chiefly birds and mammals), 

 and in particular may be mentioned the extremely fine account 

 of the Yosemite region of the Sierra Nevada by Grinnell and 

 Storer,^o i^ which are given accurate data of the distribution 

 of vertebrates in relation to life zones, together with a mass of 

 interesting notes on the ecology of the animals. 



9. There is a further important point in regard to the 

 distribution and composition of animal communities. If we 

 take the community of animals living, say, in the Canadian zone, 

 we should find that a definite percentage are confined to that 

 zone, and in fact that the distribution of some of the animals 

 is strictly determined by the type of vegetation. These 

 species we speak of as " exclusive " to that community. The 

 game-birds found in Great Britain afford good examples of 

 this. The ptarmigan {Lagopus mutus) lives in the alpine 

 zone of vegetation, while the red grouse (Lagopus scoticus) 

 replaces it at lower levels on the heather moors. Another 

 bird, the capercaillie (Tetrao urogallus), lives in coniferous 

 woods, while the pheasant {Phasianiis colchicus) occurs chiefly 

 in deciduous woods. Finally, the common partridge {Perdix 

 perdix) comes in cultivated areas with grassland, etc. We 

 see here examples of birds which are exclusive to certain plant 



