250 



NATURALIST'S GUIDE TO THE AMERICAS 



The principal mammals of the Alpine 

 summits above timberline are the Rockly 

 Mountain goat (Oreamnos americanus 

 subsp.), bighorn sheep {Oris canadensis 

 group), hoary marmot (Marmota caligata 

 group), and pika (Ocholona). 



d. Prairies. (See under Oregon.) 



e. Sagebrush semi desert. The great 

 sagebrush region of Idaho is traversed 

 by the Snake river. It is a lava desert, 

 with great extinct craters, solidified lava 

 flows, canj'ons, crevices, caves with ice, 

 super-chilled springs. 



They have as characteristic mammals 

 the co5'ote (Caiiis lestes), grasshopper- 

 mouse {Onychomys leucogaster subspp.), 

 pocket-mouse (Perognalhus), kangaroo- 

 rat {Dipodomys), ground-squirrel {Citel- 

 Ivs spp.), sage chipmunk {Eutemias 

 minimus pictus), pigmy rabbit {Brachy- 

 lagus idahoensis), white-tailed jack- 

 rabbit (Lepus townsendii) 1 black-tailed 

 jackrabbit {Lepus californicus group), 

 cottontail rabbit (Sylvilagus muttallii 

 group), and pronghorn antelope {Anti- 

 locapra americana). — L. R. D. 



Reptiles include the collar lizard 

 (Crotaphytus collaris baileyi), the leop- 

 ard-lizard {Crotophytus wislizenii), the 

 swifts {Sceloporus graciosus gracilis 

 and S. occidentalis hiseriatus), the 

 rattle-snakes (Crotolus oreganus and C. 

 conjluenlus), the bull-snake {Pituophis C. 

 catenifer), the racer {Coluber constrictor 

 mormon), and the horned toad {Phyrn- 

 osoma d. douglassii and P. platyrhi- 

 nos).—H. T. G. 



In the mountains there are innumer- 

 able small lakes, cascades, and falls. 

 Along these streams there are springs 

 both hot and cold, notably so in the 

 central and southern regions. Larger 

 lakes are Payette, Coeur d'Alene, Pend 

 Oreille, Priest and Bose. Idaho grows 

 higher from north to south, with an ele- 

 vation of about 1800 ft., in the north to 

 about 5000 ft., in the south. The only 

 "low" spot is at Lewiston (west- 

 central, near the Washington boundary), 

 lying in a canyon of 700 ft. elevation. 

 The Snake River Plains also slope down 

 from east to west, so that Idaho slopes 



down from southeast to northwest, 

 from 5000 to ISOO ft. 



/. Aquatic communities. The aquatic 

 communities present perhaps the great- 

 est variety of all. In the mountains 

 there are innumerable alpine lakes which 

 form the headwaters of precipitous 

 creeks. The creeks have dug deep 

 canj^ons, through which they tumble 

 in rapids, falls, cascades, with occasional 

 placid stretches. Such lakes and 

 streams are most numerous in the 

 Salmon River and Clearwater River 

 drainage. Swamps are found in a 

 number of the valleys throughout Idaho, 

 although none of them occupy more 

 than a few square miles of area. 



The fresh water mollusca are abun- 

 dant, especially in the northern part of 

 Idaho, in Lake Pend Oreille, and the 

 rivers and streams flowing into and from 

 this lake. Nearlj^ all are related to 

 those of eastern North America, and 

 include the genera Lymnaea, Planorbis, 

 Rhysa, Amnicola, Valvata, Fluminicola, 

 Ferrissia, Hydrobia, Pisidium, Sphae- 

 rium. Only a few Naiades are found nor 

 are the Pleuroceridae abundant, as both 

 of these groups are in the central part 

 of the United States. A few species are 

 peculiar to the region. For the ecologi- 

 cal distribution of the Lymnaediae, see 

 Baker, Monograph of Lymnaediae, 

 1911.— F. C. B. 



II. PRESENT BIOTIC CONDITIONS 



Except for the American bison and 

 perhaps the prong-horned antelope, 

 the original biota of Idaho are found in 

 at least a part of Idaho, chiefly in the 

 mountain fastnesses and the Snake 

 River Desert. 



Along the border of Washington and 

 in the central valleys of northern Idaho 

 three factors have tended to alter the 

 biota, or at least to diminish their 

 extent. These are, first, the great 

 fires which from time to time have swept 

 over millions of acres and left barren 

 wastes which are slow in reforesting 

 themselves. The second factor was the 

 discovery of gold and other precious 



