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Vegetation management on levees, especially removal of trees and shrubs, might affect burrowing mammals that are considered threats to levee integrity. We evaluated habitat associations of California ground squirrels ( Otospermophilus beecheyi) and Botta's pocket gophers ( Thomomys bottae) on levees in the Sacramento Valley to assess the effects of levee vegetation management on these species. Using burrows as an indirect measure of mammal presence, we found that the presence of trees had a negative effect on the occurrence and abundance of ground squirrels on levees, and on the location of their burrowing activities on the levee slope, potentially because visual occlusion caused by tall woody vegetation impedes detection of predators. Similarly, trees had a negative effect on the abundance of pocket gophers on levees and on the location of their burrowing activities on the levee slope, probably because of the effect of tree cover on food availability. The conversion of woodland habitats to grasslands on levees most likely will result in increased occurrence, abundance, or both of ground squirrels and pocket gophers, and thereby increase the potential threat that their burrowing activities pose to levee integrity. © 2012 The Wildlife Society. [ABSTRACT FROM AUTHOR]

Great Gray Owls (Strix nebulosa) in the Sierra Nevada Mountains feed primarily on rodents, especially voles and pocket gophers. Voles have been shown to be negatively affected by cattle grazing, but effects of grazing on gophers in the Sierra Nevada Mountains are unknown. We investigated the effects of grazing on pocket gophers (Thomomys monticola and T. bottae) in 21 grazed and 21 ungrazed montane meadow sites in the central Sierra Nevada Mountains of California. Pocket gopher densities were significantly higher in grazed meadows than ungrazed meadows. Vegetation cover and height, thatch depth, and the frequency of sedge occurrence were higher in ungrazed meadows and there were negative correlations between pocket gopher densities and these vegetation variables. We suggest that potential negative effects of grazing on Great Gray Owls could be minimized by managing meadow vegetation commensurate with the habitat needs of their prey. [ABSTRACT FROM AUTHOR]