74 DARWINISM AND HUMAN LIFE 



of those fittest for the particular conditions. 

 The struggle may be for food, or foothold, or 

 breathing-space, or what is sought after may be 

 a luxury, as is seen in the wild stampede of the 

 reindeer when the longing to visit the salt sea- 

 shore becomes irresistible many are overthrown 

 and trampled in the mad rush. 



As an instance of keen struggle between nearly 

 related species, Darwin referred to the combats 

 of rats. The black rat was in possession of many 

 European towns before the brown rat crossed 

 the Volga in 1727 ; whenever the brown rat 

 arrived the black rat had to go to the wall. Thus 

 at the present day there are practically no black 

 rats in Great Britain. Here the struggle for 

 existence is again directly competitive. It is 

 difficult to separate off the struggle for food and 

 foothold from the struggle for mates, and it seems 

 clearest to include here the battles of the stags 

 and the capercailzies, or the extraordinary lek 

 of the blackcock showing off their beauty at 

 sun-rise on the hills. 



(b) Struggle between Foes. In the locust swarm 

 and in the rats* combats there is competition 

 between fellows of the same or nearly related 

 species, but the struggle for existence includes 

 much wider antipathies. We see it between foes 

 of entirely different nature, between carnivores 

 and herbivores, between birds of prey and small 

 mammals. In both these cases there may be a 

 stand-up fight, for instance between wolf and 

 stag, or between hawk and ermine; but neither 

 the logic nor the biology of the process is different 

 when all the fight is on one side. As the lemmings, 

 which have over-populated the Scandinavian 



