Microtus mordax macrurus [Dice], Murrelet, 13:49, May, 1932.
Microtus longicaudus macrurus [Goldman], Jour. Mamm., 19:491, November 14, 1938.
Type.—Obtained at Lake Cushman, Mason County, Washington, by C. P. Streator on June 26, 1894; type in United States National Museum.
Racial characters.—Size large; tail relatively long, almost as long as head and body; color of upper parts dull brown; dorsal stripe obscure; underparts gray.
Measurements.—Two males and 4 females from the Olympic Mountains and the coast of Washington, average, respectively: total length 212.5, 220.5; length of tail 82.5, 86.8; hind foot 25.5, 24.7; ear 15.0, 13.7.
Distribution.—The Olympic Mountains, the coast region of western Washington, and the Cascade Mountains, save in the southeastern part. Marginal occurrences are: Sauk ([Taylor] and [Shaw], 1929: 24), Tye (W.W.D.), Naches River (W.W.D.), and Wind River (W.W.D.).
Remarks.—Specimens from the Cascade Mountains are referred to macrurus but are intermediate between that race and halli.
Microtus richardsoni (De Kay)
Water rat
Description.—This is the largest meadow mouse found in Washington. It is too large to be called a mouse and the term water rat, applied to it by [Merriam], suits it well. It is the only Washington microtine measuring more than 8 inches in total length. The upper parts are dark, reddish brown in color; the underparts are grayish brown. The tail comprises about one-third of the total length.
This species of meadow mouse ranges from Canada south to Colorado in the Rocky Mountains and in the Cascades south into Oregon. The water rats are strictly alpine animals, occurring about streams, marshes and damp meadows. In the Cascade Mountains they are most common in the glacial cirques where tiny streams flow through grassy meadows to plunge over the lip of the cirque on a rocky course of cascades to the valley below. Here their broad trails occur along the stream banks, commonly entering the water where it is swift. These trails are well-worn roads, usually about four inches wide but often wider. The burrows of the water rat are about three inches in diameter and are constructed with no effort at concealment; large mounds of earth mark their entrances. Freshly dug burrows are so abundant that it seems likely more are dug than are actually inhabited. Burrows are often dug beneath rocks.