THE TAIGA AND ITS FAUNA 37 



the rigour of the winter climate. The thick branches 

 may shelter the ground from snow, the covering of 

 dead leaves may protect it from frost ; hollow trees 

 and dense bushes offer protection to many small 

 animals. In short, while the forest does not offer the 

 rich pasturage of the steppe in summer, it offers greater 

 advantages in winter, and especially greater reserves 

 of food. 



One result of this is that on the whole the habit of 

 migration is less marked in the animals of the temperate 

 forest than in steppe ones. It does occur, but, on the 

 other hand, both tundra and steppe animals may seek 

 the forest in winter, and the greater uniformity of con- 

 ditions in the forest prevents migration occurring on 

 the same scale as in steppe and tundra, where areas 

 of abundance even in the summer season alternate 

 with others where famine reigns. 



As a consequence of the fact that the forest offers 

 a refuge to animals from other areas, we find that its 

 denizens may be divided into two groups. We have 

 forms like the squirrel, the dormouse, the lynx, the 

 woodpecker, the tree-creeper, the tree-frog, and so 

 forth, which are structurally adapted for forest life, 

 and are not at home elsewhere, and we also find animals, 

 like some kinds of deer and wolf and fox, which show 

 no very special adaptations to forest life, but which 

 visit the forest for shelter or for food. 



We have already noted that the northern limit of 

 the forest is determined by adequate summer warmth. 

 Its southern limit depends upon much more complicated 

 factors, especially upon the rainfall, and the absence of 

 drying winds in winter, when the coldness of the soil 

 prevents absorption. A small rainfall, limited to the 

 summer months, favours grass rather than trees, and 



