530 



NATURALIST'S GUIDE TO THE AMERICAS 



the precipitation on some mountain 

 ranges is probably well above 20 to 25 

 in. Under these conditions the climate 

 is varied, though predominantly cool 

 and mainly arid. The vast treeless 

 plains are level or rolling and are located 

 for the most part in the southern half 

 and in the eastern portions of the state; 

 in the eastern portions the rainfall is 

 sufficient to give the plains the character 

 of grassland steppe, but the plains of 

 the central and western regions are 

 characterized by sagebrush desert which 

 gives place on the foothills and lower 

 mountain slopes to juniper and semi- 

 desert coniferous forest. The mountain 

 ranges are found chiefly in the northwest 

 part of the state. Their middle slopes 

 are usually covered with mountain 

 coniferous forest and these merge into 

 the treeless crests and peaks above 

 timberline where alpine conditions pre- 

 vail. Three great river systems have 

 their sources in the mountains of Wyom- 

 ing and the heavy snowfall of the moun- 

 tains helps to make a well watered state, 

 considering prevailing arid conditions. 

 The life zones in Wyoming as out- 

 lined by Gary include the following: 

 (1) A zone occuping the low plains and 

 most of the valleys in which the yucca 

 (Yucca glauca), rabbit brush {Chryso- 

 thamnus), salt-bush (Atriplex spp.), 

 juniper, broad leaved Cottonwood {Popu- 

 lus occidentalis) and willows are charac- 

 teristic {Upper Sonoran). (2) A zone, 

 comprising fully half of the state, 

 embracing the high sagebrush and 

 grassy plains, the basal slopes of the 

 mountains and most of the foothills, and 

 characterized by sagebrush {Artemisia 

 tridentata) , the narrow-leaved cotton- 

 wood {Popuhis anguslifolia), and west- 

 ern yellow pine {Pinus scopulorum) 

 {Transition) . (3) A zone covering the 

 middle mountain slopes (Montane Belt) 

 and the highest foothill ranges and 

 characterized by forests of lodgepole 

 pine {Pinus murrayana), aspen {Populus 

 tremuloides), and, higher up, spruce 

 {Picea engelmanni) and alpine fir {Abies 

 lasiocarpa). A rich fauna and flora 

 is present {Canadian). (4) A compara- 



tively narrow zone in the timberline 

 region (subalpine), characterized by 

 dwarf Engelmann spruce, alpine fir 

 and white-barked pine {Pinus albicaulis) 

 {Hudsonian). (5) A zone consisting of 

 the mountain peaks and crests above 

 timberline with no trees, but where soil 

 is present and alpine grasses and flowers 

 flourish {Arctic-Alpine). For lists of 

 animals see references below. 



II. PRESENT BIOTIC CONDITIONS 



At one time the large game animals 

 and game birds were very abundant. 

 Gountless herds of bison and pronghorn 

 antelope roamed the plains. Now, 

 bison are found only in Yellowstone 

 Park and in one or two private herds. 

 Antelope and elk in spite of protection 

 are being rapidly decimated; bear, deer 

 and bighorn sheep are growing scarce; 

 mountain goats and moose are nearing 

 extinction; hawks, eagles and all kinds 

 of game birds are much less abundant 

 than formerly; prairie-dogs, ground- 

 squirrels, wolves and coyotes are being 

 exterminated by the U. S. Biological 

 Survey. Great flocks of sheep and 

 herds of cattle graze on the plains and 

 in the foothills, and in parts of the 

 National Forests, and many natural 

 areas are being altered by too close 

 grazing. Some areas, principally bor- 

 dering Yellowstone National Park, are 

 still largely in a primitive condition 

 except for diminishing large game and 

 the introduction of trout. Remote 

 open deserts are also almost untouched. 

 For present distribution of life at various 

 altitudes see Gary's Life Zone Investiga- 

 tions in Wyoming. In nearly all sec- 

 tions, close grazing and in the valleys, 

 agriculture are changing natural con- 

 ditions. Timber cutting under re- 

 stricted conditions is allowed in some 

 of the National Forests. 



III. BIRD RESERVATIONS 



Three are known to the writer. The 

 Shoshone Bird Reservation, located in 

 Park Gounty, on the Shoshone River, 

 above the Shoshone dam; water fowl 



