104. Northern grasshopper mouse 323 105. Western harvest mouse 325 107. Deer mouse 329 108. Bushy-tailed wood rat 335 109. Northern lemming mouse 337 110. Heather vole 339 111. Gapper and California red-backed mice 342 113. Pennsylvania meadow mouse 346 114. Montane and Townsend meadow mice 348 116. Long-tailed meadow mouse 352 117. Water rat 356 118. Creeping mouse 357 120. Muskrat 362 122. Mountain beaver 368 124. Big jumping mouse 372 125. Porcupine 375 126. Pika 378 127. Snowshoe rabbit 383 128. Black-tailed jack rabbit 386 129. Nuttall cottontail 388 INTRODUCTION Mammals of Washington are of especial interest to the naturalist because many of them are recent immigrants; much of Washington was buried under thick glacial ice until relatively recently and many of the mammals, therefore, have inhabited the area only since the ice disappeared. The evolution or development of certain subspecies, in Washington, has certainly occurred within the last few thousand years. To be able thus to date such evolutionary changes as have occurred is of course a matter both of importance and interest to zoölogists. The evolutionary changes in several species are relatively great. In color, for example, the bobcat in the humid coastal area of western Washington is notable for its dark coloration, whereas in the more arid area of southeastern Washington it is remarkably pale and of a different subspecies. Within the limits of the state of Washington, elevations ranging from sea level to more than 14,000 feet occur. Since different elevations have their characteristic mammals, more kinds are found in Washington than in other areas of corresponding size that lack such topographic diversity. Expressed in terms of the life-zone concept, Washington includes faunas ranging from the Upper Sonoran Life-zone to those of the Arctic-Alpine Life-zone.