Reasons why the second hypothesis is inadequate are: (1) Raccoons range but little north of the state of Washington, both east and west of the Cascades. (2) Raccoons of western Washington and the area about San Francisco Bay, California, are as much alike as are raccoons from southwestern Washington and northwestern Oregon. It is thought that raccoons, if resident in western Washington since interglacial time, would have developed strong racial characters, and the fact that they have not indicates that they have entered the state at a relatively recent date.
The raccoon of eastern Washington (excelsus) is a member of the Great Basin Fauna and has probably included southeastern Washington in its natural range for a long period of time. The raccoon has not extended its normal range into northeastern Washington, although it is seemingly ideal raccoon habitat; only an occasional vagrant occurs there. A stock of raccoons from which emigrants might come has existed in southeastern Washington and the Yakima Valley for some time. The Columbia River might serve as a highway by which emigrants could reach northeastern Washington.
Martes caurina.—The earlier distributional history of the western marten has been postulated by [Davis] (1939: 131-132), who stated: "When the ancestral stock split into the two groups, the one that gave rise to americana may have pushed eastward across Canada to the Atlantic Coast; the other, giving rise to caurina, may have migrated southward along the Sierra Nevada-Cascade and Rocky mountains. Perhaps the great ice sheet was instrumental in pushing americana eastward and separating it geographically from caurina." The present occurrence of americana in Alaska and British Columbia is thought to have been by invasion from the east in postglacial time.
[Davis]' theory seems basically correct but subject to correction in detail. The presence of caurina in the southern Rocky Mountains suggests that it is not a Pacific Coastal species in the common sense. Had americana occupied northern British Columbia in pre-Wisconsin Time, it and not caurina would be expected to occur in the southern Rocky Mountains today, for the form found in British Columbia almost certainly would have been forced into the Rockies. The range now occupied by caurina in the Rocky Mountains is so extensive as to suggest that martens could not have migrated into all of it from the Pacific Coast since Vashon Time, even had the region been unoccupied by any species of marten. The presence of americana in Alaska and British Columbia suggests that it arrived in those areas before caurina and that had the Rocky Mountains been unoccupied by martens in pre-Wisconsin time, americana and not caurina would have reached the Rockies first. It appears that caurina occupied much of western North America in pre-Wisconsin Time and was forced southward into the southern Rocky Mountains and along the Pacific Coast by Vashon-Wisconsin ice.
The separation of americana and caurina may be supposed to have occurred before the pre-Vashon-Wisconsin interglacial interval, perhaps by a glacier similar to but antedating the Vashon-Wisconsin glaciation.
The martens of western Washington (Martes caurina caurina) are a coastal race. Those of northeastern Washington belong to a race of the Rocky Mountain Fauna, and are referred to M. c. origenes. [Davis] (1939: 132) refers the martens of Idaho to Martes caurina caurina. I have compared specimens from Idaho with animals trapped for fur from the Pacific Coast proper and feel that the animals from northeastern Washington and those from Idaho are more like origenes than caurina, although perhaps not typical. The animals from the Pacific Coast proper are caurina and have darker heads and brown instead of yellow patches on the throat.
Martes pennanti.—Fishers are found throughout the Cascade Mountains and probably were widely distributed over western North America in pre-Wisconsin Time.
Mustela erminea.—The distribution of ermines along the coast of northern California and in the Cascade-Sierra Nevada of Oregon and California indicates, as does their differentiation there, that they ranged southward to these areas before and during Vashon-Wisconsin Time.