STEPPES OF ASIA AND AMERICA 55 



almost throughout tUl man interfered, though the steppe 

 region of Asia is continued into it through Southern 

 Russia and part of Hungary. We find then that since 

 the close of the glacial period Europe has been con- 

 tinually liable to incursions of steppe animals from 

 Asia, some of which, like the hamster, have kept their 

 hold, while others, like the saiga antelope, rapidly 

 died out. 



Another character of the animals of the temperate 

 steppe is the prevalence of hibernation among them. 

 The tundra is too cold for hibernation to be practised 

 to any great extent, and the shelter and presence of 

 food even in winter in the forest makes it relatively 

 infrequent there. But the animals of the steppe can 

 only find in burrows and in sleep protection against 

 want of food and extremes of temperature, so that here 

 both aestivation and hibernation may occur. The 

 squirrels in the fir woods wake whenever the temperature 

 rises in winter, just as the fir-tree itself becomes active 

 whenever the temperature permits. But the plants of 

 the steppe disappear beneath ground so soon as their 

 brief period of activity is over, and their quiescence is 

 reflected in that of many of the steppe animals. 



Large areas of land almost devoid of trees, and 

 clothed, at least at times, with grasses and herbs, occur 

 in many other . temperate regions besides Asia and 

 South-eastern Europe. A great area of land of this 

 type extends from the border of the Canadian forest 

 southwards through the United States in th^ region 

 west of the Mississippi river, nearly to the Gulf of 

 Mexico. Similar areas occur in the Argentine and in 

 Patagonia in South America, in South Africa, and in 

 the south-eastern part of Australia. By extension the 

 term steppe can be applied to aU these regions, and 



