STEPPE FAUNAS OP ASIA AND AMERICA 53 



food, and also a seasonal and local scarcity. If the 

 rains of early summer are abundant in the steppe there 

 is an extraordinarily rapid awakening into life on the 

 part of the steppe plants, resulting in a great abun- 

 dance of food for the herbivores of the region. If the 

 rains fail, scarcity reigns, and it comes in any case as 

 soon as the favourable season is past ; that is, alike in 

 the height of summer and in the depth of winter. But 

 local conditions produce minor variations in climate, 

 altitude being one of the most important of these con- 

 ditions. For this reason there are frequent alternations 

 of famine and plenty, alike in time and space. Like 

 the tundra animals then, the steppe animals tend to be 

 social, to move about in flocks from one region of 

 abundance to another. But as the wealth of the steppe 

 is greater than that of the tundra, they are far more 

 numerous, and far more diverse. Like the tundra 

 animals as a whole, they attempt to escape unfavour- 

 able conditions by migration, and as these migrations 

 must be rapid, to prevent death by starvation occurring 

 between one region of pasturage and the next, the 

 steppe animals are mostly swift, with special adapta- 

 tions to ensure rapidity of movement. 



The herbivores, always, as we have seen, necessarily 

 the majority, are far more exposed in the open steppe 

 than in the forest, and therefore they are either bur- 

 rowers, or have singularly keen senses, enabling them 

 to perceive danger from afar. The social instinct also 

 is here of great aid. In some cases, as with the wild 

 asses, the strength of the male enables him to protect 

 the females and young from attack. As the safety of 

 the species depends in this case upon the strength of 

 the male, we find that he must win and keep his post 

 as leader and defender by his strength, and that he is 



