64 STEPPE FAUNAS AND TEMPERATE 



to modify the condition of the soil, so that special 

 plants appear in the ' marmot gardens ', which can 

 thus be recognized from afar. The hemp-leaved nettle 

 and wild rhubarb occur especially here, and the presence 

 of the large leaves of these plants among the lyme 

 grass (Elymus) of the steppes is a very obvious feature, 

 while the loosening of the soil by the burrows makes 

 progress for horsemen very difficult over the ' gardens '. 



The interesting pomt is that rodents of similar habits 

 seem to inhabit steppe regions in general. Thus the 

 prairie marmot (Cynomys Ivdovicianus), a related form 

 inhabiting the prairies of North America (Fig. 9), has 

 similar habits, while the viscacha of the pampas of 

 Argentina, though not very nearly related, shows also 

 a general resemblance in habits, and also modifies the 

 herbage in the regions of its occurrence. 



A different, though no less perfect, adaptation to 

 steppe hfe is shown by the jerboas or jumping mice. 



In speaking of the marmots we noted that for rapid 

 and efficient burrowing, short fore-legs are necessary, 

 but, on the other hand, if the hind-legs are also short, 

 the animal's range of vision is small, and its speed 

 cannot be great. On the other hand, if the legs are 

 elongated to give speed, then feeding on the ground 

 and drinking become difficult, as is seen in the giraffe 

 (Fig. 36). The jerboas show a curious form of compro- 

 mise to these varying needs, generally parallel to that 

 shown by the kangaroo, which is, however, not a 

 burrowing animal. In the jerboas the fore-limbs are 

 short, thus permitting the animal to burrow, but the 

 hind-legs are enormously long (Figs. 37 and 38), and the 

 tail also long and capable of helping in the support of 

 the body. The animal therefore progresses by leaps, the 

 fore-legs not touching the ground at all. In feeding. 



