Introduction 



Passage of the Federal Endangered Species Act of 1973 and subsequent recognition of 

 the value of conserving biotic diversity (Wilson 1988) have resulted in many government 

 agencies becoming active in species conservation. Surveys to determine the location and size 

 of populations of rare species are being conducted on public lands throughout the west. 

 These surveys are necessary in any species conservation program; however, knowing the 

 location and size of populations at any one point in time is only the first step in a long-term 

 protection strategy (Sutter 1986). Extinction is a process requiring an understanding of 

 population dynamics (Menges 1986). Periodic inventories can detect trends but will do little 

 to determine causality or help generate predictive hypotheses (Palmer 1987). Long-term 

 conservation requires a knowledge of many life history parameters including fecundity, 

 recruitment, survivorship, age structure, and population flux. Demographic monitoring 

 techniques can provide information on factors regulating population density and persistence 

 (Palmer 1987). This information, in turn, provides an essential basis for management 

 decisions. 



Astragalus scaphoides (Jones) Rydb. (Bitterroot milkvetch) is endemic to a small area 

 of east-central Idaho and adjacent Beaverhead County, Montana. It is a candidate for listing 

 as a threatened or endangered species (C-2) by the U.S. Fish and Wildlife Service (USDI- 

 FWS 1990). It is listed as sensitive in Idaho (Moseley and Groves 1990) and Montana 

 (Lesica and Shelly 1991). Most populations of A^ scaphoides in Montana are on public lands 



