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. [Illustration: 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_. [Illustration: 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.)] THE HUDSONIAN LIFE-ZONE In Washington the Hudsonian Life-zone is of greater diversity than any other. Frost and steep slopes have formed great masses of talus and, in this talus, certain species of mammals, such as _Ochotona princeps_, _Marmota caligata_ and _Marmota olympus_ are found. Other species, such as the golden-mantled ground squirrels, mountain chipmunk, bushy-tailed wood rat, red-backed mouse and long-tailed meadow mouse find the talus an ideal home. Glacial action has produced, in the Hudsonian Life-zone, numerous level or concave areas that contain small lakes and slow-moving streams. Dense, herbaceous vegetation is abundant nearby. Small mammals abound and a line of mouse traps will almost certainly catch a few such typical species as: _Sorex palustris_, _Sorex obscurus_, _Microtus oregoni_, _Microtus richardsoni_, _Microtus longicaudus_ and _Zapus princeps_ as well as the ever present _Peromyscus maniculatus_. The shrew-mole or heather vole might also be taken, though the latter is more apt to be found in nearby heather meadows. TABLE 1. Distribution of mammals in Washington by Life-Zones. _A._ Abundant. _C._ Common. _R._ Rare. Column headers: A: Humid Transition B: Arid-timbered Transition C: Arid-grasslands Transition D: Upper Sonoran E: Canadian F: Hudsonian