ANIMAL DISTRIBUTION 



475 



The vertical or altitudinal distribution of terrestrial animals de- 

 pends primarily upon the vertical distribution of the vegetation. 

 The variation in the kinds of plants found at different altitudes de- 

 pends to a large extent upon the climatic belts which extend around 

 the earth between the equator and the poles. The vertical belts of 

 plants encountered in traveling from a lowland to a high mountain 

 top correspond very closely to the climatic zones surrounding the 

 poles of the earth. The communities of animals and plants found in 

 each vertical zone are similar throughout the world. 



The seven vertical life zones and a few of the characteristic animals 

 and plants found in each zone, as it is represented in the Southwest, 

 are here given. 



MUDSONIAM 



,. vo*'%n ><>>itt»i>n 



UA t-IVlL 



ALi»ise ^' 



HUOSONIAH 12- 



CANADIAN 



TRANSITION "* 



10- 



9- 



»- 

 7* 

 6- 

 5- 



4- 

 J- 



2- 



1- 



Fig. 205.— Diagrammatic sections of the Grand Canyon and San Francisco peak 

 showing the vertical life zones. (After N. N. Dodge and Merriam. ) 



1. The Alpine zone (usually above 10,500 feet) is the area above 

 the timber line. This highest zone is represented in the Southwest 

 on the top of San Francisco Mountain in Northern Arizona and in 

 the Sangre de Cristo range of the Rockies in Northern New Mexico. 

 This zone is characterized by the presence of few plants, such as 

 saxifrages and dwarf willows. Among the fauna are found the 

 golden eagle, some weasels, and mountain sheep. 

 ■ 2. The Hudsonian zone (9,000-10,500 feet) consists of a forest of 

 spruces and some firs, and harbors the dusky horned owl, bears, 

 shrews, and red squirrels. The Hudsonian zone is found in the same 

 region as the Alpine zone. 



3. The Canadian zone (8,000-9,000 feet) is distinguished by the 

 presence of the Douglas fir and the aspens. Common animals of this 

 zone are the three-toed woodpecker, one species of shrew, and two 



