Other than the muskrat, the water vole is the largest arvicoline in Oregon. It occurs in the Cascade Range from Mt. Hoot to Mt. Mazama and in the Wallowa and Blue mountains east and north of a line connecting Langdon Lake, Umatilla County; the North Fork Malheur River, Grant County and Cornucopia, Baker County. It is considered an inhabitant of alpine and subalpine streamsides.

The water vole is active throughout the diel cycle; however, activity is least from dawn to midday, rises during the afternoon, and peaks at night, probably after midnight. It is a good swimmer and can swim against the current in small streams both on and below the surface.

Photo by Peter Trimming, Wikipedia