A description of the small mammal community (Orders Rodentia and Insectivora) in the Hells Canyon Study Area

Publication Type:

Report

Authors:

Holthuijzen, Anthonie M. A.

Source:

Hells Canyon Complex FERC No. 1971, Idaho Power Company, Issue Revised, Boise, ID, p.42 (2003)

Call Number:

U03HOL01IDUS

Keywords:

bushy-tailed woodrat, Deer Mouse, Great Basin pocket mouse, Microtus montanus, montane vole, Neotoma cinerea, Perognathus parvus, Peromyscus maniculatus, Reithrodontomys megalotis, Sorex vagrans, vagrant shrew, western harvest mouse, Western Jumping Mouse, Zapus princeps

Abstract:

In April of both 1997 and 1998, small mammals were sampled at nine sites along 30 trap lines in the Hells Canyon Study Area (sites between Grouse Creek and Pittsburgh Landing, on OR and ID sides of the Snake River). Objectives were to determine relative abundance and distribution of small mammals, community composition of the small mammal community, and habitat relationships between dominant cover types and the small mammal community. Trap lines were placed in all available cover types at each site, and nine cover types were sampled. Trap lines consisted of 25 stations set 10 m apart, with two traps at each station. A cluster sampling approach was taken at each sample site (i.e., a simple random sample in which each sampling unit is a collection or cluster of elements [in this study, cover types]; clusters were defined as those sample areas that were accessible and contained the maximum number of habitat types). The sites covered at least 10 ha (25 ac); all cover types of potential importance as small mammal habitat were sampled. Eight species of small mammals were trapped along trap lines. The most abundant species caught was the deer mouse (81.1%), followed by the montane vole (9.3%), western harvest mouse (4.8%), and vagrant shrew (3.4%); the others were caught in very small numbers (< 1%): Great Basin pocket mouse, western jumping mouse, bushy-tailed woodrat, and long-tailed vole. Four species were reported from the three pit-fall sites: the vagrant shrew, montane vole, deer mouse, and northern pocket gopher. Many other species were observed or caught incidentally and documented. Species diversity differed considerably among cover types. The highest diversity was found in the Mountain Shrubland cover type and the lowest in Shore & Bottomland Wetland. Species diversity was highest in the reach below Hells Canyon Dam compared with species diversity for the other two reaches (called Hells Canyon Reservoir and Brownlee Reservoir reaches). The study was done to provide Idaho Power Company with the information necessary to relicense the Brownlee, Oxbow, and Hells Canyon dams with the Federal Energy Regulatory Commission (FERC).