Date of Award:

5-1-1976

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Department name when degree awarded

Biology & Ecology

Committee Chair(s)

James A. MacMahon

Committee

James A. MacMahon

Abstract

Rodents were live-trapped in 2.7 ha grids in five Great Basin desert shrub communities in NW Utah during June, July, and August, 1974. The eight species captured, in decreasing order of abundance, were: Dipodomys ordii, Peromyscus maniculatus, Perognathus parvus, Eutamias minimus, Reithrodontomvs megalotis, Onychomys leucogaster, Neotoma lepida, and unknown. For each grid, mean monthly density for each rodent species, species diversity (Shannon-Wiener), and total animals captured were compared to various vegetation and soil characteristics. Densities in the first four species correlate significantly with different environmental variables. Rodent species diversity correlates primarily with shrub height diversity, average shrub height, and shrub density. Total number of individuals captured correlates primarily with shrub height diversity, average shrub height, shrub density, and shrub/herb species diversity. Ordinations of grids by rodent and vegetation factors by means of principal component analysis substantiate correlations between rodent community characteristics and shrub density, average height, and height diversity, and shrub/herb species diversity. Importance Values were calculated for rodents and vegetation in each grid; these values were used to compute similarity values between grids and trapping periods. For rodents, between-trapping-period similarity slightly exceeds between-grid similarity. Between-grid similarity for rodents exceeds that for vegetation, indicating that rodents respond significantly to non-vegetation factors. Shrub height diversity may reduce predator visibility. It may allow finer subdivision of resources by different species or reduce intraor interspecific competition. Greater average shrub height, including the number of shrubs 46 to 90 cm high, increases resources (productivity) available for rodent use. Scansorial species may exploit this resource, possibly reducing competition between climbing and non-climbing species. Higher shrubs may also reduce predator visibility. Number of rodent species and equitability of number of individuals per species may both be affected by shrub height diversity and average shrub height. The positive effect of low shrub/herb species diversity and low shrub density on rodent community characteristics is not understood. Suggestions are given for increasing the effectiveness of future studies of rodent-habitat relationships.

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