adjacent river breaks and uplands. The eastern boundary ends in 

 the vicinity of the Robinson Bridge crossing of the Missouri 

 River . 



The Marias River from the north, including its tributary the 

 Teton River, and the Judith River from the south are the principal 

 tributaries entering the Missouri River in the study area. Other 

 tributary drainages entering the Missouri River from the north in 

 this area include: Little Sandy, Eagle, Chips, Birch, Bullwhacker 

 and Cow creeks. Belt, Highwood, Shonkin, Arrow, Dog, Two Calf 

 and Armells creeks enter from the south. 



The study area includes portions of Chouteau, Cascade, Fergus, 

 Blaine and Phillips counties. 



P hysiography 



The greater part of the study area lies in the glaciated por- 

 tion of the Great Plains. It is characterized by broad, rolling- 

 to-broken divides sloping gently toward the Missouri River. The 

 Missouri River flows through a relatively deep valley varying from 

 500-1,000 feet below the average elevation of the adjacent plains. 

 The soils are extremely unstable and erosion and tributary drain- 

 age have produced highly dissected, rough terrain, resulting in 

 spectacular, varied, and scenic badlands and breaks ranging from 

 2-10 miles in width immediately adjacent to the river valley along 

 both sides of the Missouri River, and of lesser width along tribu- 

 tary streams. This greatly eroded section of the region is com- 

 monly known as the Missouri River Breaks (Department of the In- 

 terior 1975) . 



Climate 



The climate is semi-arid. It is marked by wide seasonal fluc- 

 tuations in precipitation and temperature, by recurring drought, 

 a relatively short growing season, 120-135 days, and a high pro- 

 portion of sunny days. Precipitation averages about 13.5 inches 

 annually, and more than 70 percent occurs between March 1 and Sep- 

 tember 1. About 7 inches of the annual total falls during the 

 months of May, June and July. Summer temperatures are moderate, 

 usually hot in the daytime and cool at night. Fall months are 

 generally open and dry. Very little snow falls before October. 

 Winters are cold, with light to moderate snowfall (about 40 inches) 

 occurring over an average season. Low temperatures are frequently 

 dispelled by moderating winds known as "chinooks." The Missouri 

 River below Fort Benton is usually frozen over by December and 

 does not thaw until April (Department of Interior 1975) . 



During the report period, the study area experienced two ex- 

 tremely severe winters, 1977-78 and 1978-79. Since these winters 

 had a major influence on wildlife, the following description of 



