STEPPE FAUNAS OF 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 
