STEPPES OF ASIA AND AMERICA 63 
so the upper parts of mountains form steppes because 
the elevation prevents forest growth. Again, it is 
believed that in those parts of the world recently sub- 
jected to glaciation there was a period, after the retreat 
of the ice, when the climate was unsuited to trees, lead- 
ing to a wide extension of steppe conditions. This 
brought in its turn a wide extension of steppe animals, 
which, with the gradual improvement of the climate, and 
the return of forest-haunting forms, were driven up 
the mountain sides to the Alpine regions. If this be so, 
then the shrill whistle of the Alpine marmot, so common 
a sound in the mountainous regions of Switzerland in 
summer, not only recalls the conditions of the Asiatic 
steppes, but also brings back a time when much of 
Europe was in the condition in which the steppes are 
to-day. The Alpine marmot is now limited to the Alps, 
Pyrenees, and Caucasus, the time being far past when 
it also inhabited the low ground. On the other hand, 
the bobac (A. bobac), the characteristic marmot of the 
Asiatic steppes, extends into Europe as far as the 
eastern frontier of Germany. 
Marmots are rather clumsy animals with heavy 
bodies, short limbs, and usually short tails. The short- 
ness of the limbs must greatly limit the range of vision, 
and the animals have very markedly developed that 
habit of sitting up on the hind limbs to take a wider 
view which is common in relatively short-legged animals. 
The shortening of the fore-limbs here gives greater 
purchase in burrowing, the burrows being extensive. 
The food appears to be entirely vegetable, and the 
animals hibernate much more profoundly than the 
susliks. Bobacs occur in very large colonies, and 
tunnel the ground in all directions with their burrows. 
According to Kobelt, the result of these excavations is 
