necessary to know what the ideal population level is, and when 

 it has been reached. What constitutes a sustained-yield harvest of 

 this population, and how to attain and recognize it must be 

 determined. 



The proper population level is determined by the welfare of the 

 animal itself and by its value to man. An ideal balance between a 

 minimum and a maximum population must be quantitatively resolved 

 to provide for the beaver's welfare. Soil and water conservation, 

 sport fisheries, wildlife habitat development, fur and other positive 

 values, as well as the negative values of agricultural conflict, timber 

 destruction, road damage, stream obstruction, etc., must be quan- 

 titatively expressed to properly determine the ideal population level. 



Part of the beaver research conducted by the Fur Resources 

 Section is directed toward this problem of pop- 

 Beaver Research ulation levels. Results on beaver "carrying capa- 

 Directed Toward city" studies in the Jefferson Basin are giving 

 Carrying Capacity the determinants of the population level con- 

 ducive to the welfare of the beaver. Through 

 these studies it is possible to understand some of the factors of 

 population levels and to better define an ideal situation. 



Maximum sustained yield cropping is determined by the annual 

 net increment of an ideal population. It is difficult, however, to know 

 when a beaver- harvest constitutes sustained-yield cropping. Mon- 

 tana's research on this problem includes age-ratio methods develop- 

 ment, aerial colony count trend analysis and beaver harvest analysis. 



The age-ratio of a beaver population will change under varying 

 intensities of trapping. A method of determining age-ratio figures 

 through pelt-measurement analysis was developed by section per- 

 sonnel and is now in use on a state-wide basis. "'^ 



Annual state-wide aerial colony counts were initiated in the fall 

 of 1953. These counts constitute only an index designed to help 

 determine population trends and thus the relative intensity of 

 cropping. Approximately one-fifth of the state's beaver habitat is 

 involved in this operation. Results of the first count indicated that 

 over half of the state contains a "maximum" beaver population. 



A comprehensive harvest analysis is conducted at the end of 

 every season. This shows the number trapped, dates of capture, 

 trapper success and the ratio of piivate land to public land utilized, 

 for every beaver trapping area. 



Through these studies of age ratios, aerial colony count trends 

 and harvest analysis, the status and trend of beaver populations can 

 be determined and within reasonable limts the status of harvests 

 in relation to sustained-yield cropping can also be ascertained. 



In the last two years beaver management in Montana has shown 

 considerable progress. Much of this progress can be directly attrib- 

 uted to the research and planning of the Fur Resources Section. The 

 Fish and Game Department's program will continue to improve as 



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