34 THE TUNDRA AND ITS FAUNA 



upon cuttles and crustaceans. The white whale (Delphin- 

 a/pterus leucas) is similarly an Arctic form, remarkable 

 for its habit of ascending rivers for a considerable 

 distance. The kiUer whale {Orca gladiator), on the 

 other hand, which is a very widely distributed animal, 

 chiefly occurs in the Arctic in summer. 



If we sum up the facts in regard to the distribution 

 of tundra animals, and of the marine forms which 

 occur round its seaward margin, we may say briefly 

 that the tundra fauna is virtually uniform throughout. 

 The animals, generally speaking, are either circiunpolar 

 at the present time, or have once been circumpolar, 

 and there is no distinction between eastern and western 

 faunas. In other words, the fact that the ' salt, estrang- 

 ing sea ' is here more or less ice-bound makes the land 

 areas virtually continuous, and this, combined with the 

 marked uniformity of physical conditions, leads to 

 practical uniformity of distribution, both of plants and 

 of animals. No such similar uniformity exists in regard 

 to the.other natural regions of the world. Though the 

 steppes of Asia show a general resemblance in physical 

 conditions to the steppe-like regions of North America, 

 yet their faunas are different. In the same way, the 

 faunas of the similar equatorial forests of South America 

 and Africa are markedly dissimilar, and there is almost 

 no resemblance between the desert fauna of Australia 

 and those of Africa or of America. No resemblance, 

 that is, when the actual affinities of the animals are 

 considered, but necessarily desert animals or forest 

 animals, whatever their affinities, share certain adapta- 

 tions to forest or desert life. 



Eefeeencbs. Accounts of tundra animals are to be found in almost 

 all books dealing with the Arctic regions. The foUowing may be men- 

 tioned as giving a considerable amount of detail : Marnial of the Natural 



