Marshes are not uncommon on the Columbian Plateau and elsewhere in the Upper Sonoran Life-zone in Washington. They do not possess a fauna that is strictly Upper Sonoran but instead contain species more typical of the Arid-timbered subdivision of the Transition Life-zone. Meadow mice found in desert marshes include Microtus montanus and Microtus pennsylvanicus. The only shrew we have found is Sorex vagrans. The harvest mouse (Reithrodontomys megalotis) is often abundant in marshes.
Fig. 15. Upper Sonoran Life-zone, sand and basalt cliffs along the east bank of the Columbia River, at Vantage, Washington, 1930. (Fish and Wildlife Service photo by Victor B. [Scheffer], No. 848.)
The Canadian Life-zone
The Canadian Life-zone is a relatively uniform area in which the forest habitat is most important. Talus and swift, cold streams bring some typical mammalian species into the Canadian Life-zone from the Hudsonian. Mammals are usually common; they are abundant only in the upper portion of the Life-zone. Arboreal species and forms adapted to life beneath the forest cover are dominant. The Douglas squirrel, red squirrel, northern flying squirrel and Townsend chipmunk are typical arboreal species. Traps set beneath the trees might catch Peromyscus maniculatus, Clethrionomys gapperi, Neotoma cinerea, Sorex obscurus, or Sorex trowbridgii.
Fig. 16. Canadian Life-zone forest on Mount Rainier, Washington, elevation 2,800 feet, September 14, 1934. Western hemlock, Douglas fir, western red cedar, and grand fir. (Fish and Wildlife Service photo by Victor B. [Scheffer], No. 325.)