Chapter III: Part 3

The known facts of this movement were sufficiently impressive to cause the author to study rather closely the distribution of mammals in this area. The collection of bones from a cave along the Columbia River near Vantage, Grant County, on the Columbian Plateau, is especially helpful in this respect. This cave was first visited in 1938. It had been the habitat of owls, bats, and primitive man. The floor of the cave was buried under from one to three feet of bat guano, much of which had been hauled away for fertilizer. Here and there we found traces of fire and occasional piles of mussel shells. Some arrowheads and one beautiful obsidian spear head were found, all buried in guano and about midway between the floor and the top of the deposit. Remains of mammals were abundant through the bat guano, and apparently had been brought to the cave both by man and owls. The jaw of a mountain sheep was found. This species was known to be present when the first settlers reached the area (Cowan, 1940: 558). The remains of smaller mammals included gopher, pocket mouse, muskrat, meadow mouse, deer mouse, coyote and white-tailed jack rabbit. No remains of cottontail, black-tailed jack rabbit or harvest mouse were found. The absence of the cottontail was especially surprising, in that fully thirty skulls of white-tailed jack rabbits were noted. The grasshopper mouse (_Onychomys_) was also absent, but this species is not common. The two rabbits and the harvest mouse, however, are abundant in the area today. The cottontail and harvest mouse have only recently been recorded from the Okanogan Valley of British Columbia (Cowan and Hatter, 1940: 9). The black-tailed jack rabbit has never been taken there.

Apparently then, some species have only recently entered the Upper Sonoran Life-zone of eastern Washington. They have, of course, reached the state from Oregon. The first step in the invasion probably was the occupation of southeastern Washington. No barrier prevents mammals from reaching southeastern Washington from eastern Oregon but the Columbia to the north and west prevents them from occupying the Yakima Valley, and the Snake River prevents them from reaching the Columbian Plateau. The kangaroo rat, Great Basin striped skunk and Great Basin spotted skunk now are at this stage of invasion. The second stage was the crossing of the Columbia River to the Yakima Valley. This has been accomplished by the black-tailed jack rabbit and, earlier, by the pocket mouse, _Perognathus parvus parvus_, and ground squirrel, _Citellus townsendii_. The third stage was the crossing of the Snake River and occupation of the Columbian Plateau. The final stage is the crossing of the northern Columbia River and occupation of the Okanogan Valley.

SPECULATION AS TO THE LATER DISTRIBUTIONAL HISTORY OF THE MAMMALS

Whereas it is probable that a few of the species now occurring in Washington evolved there, most are immigrants from other areas. The success of a given species in any area is dependent on numerous factors which may be classified under food, shelter from the elements, protection from enemies and safe breeding places. The factors may be of an inorganic nature, such as climate, soil and exposure or they may be organic, such as vegetation, competition for food and response to enemies. Abundance results in population pressure and a tendency for the range of a species to expand.

Mammalian populations are dynamic and change in accordance with alterations in environment. Because the later geologic history of the state of Washington was violent, with resultant changes in climate and geography, the mammalian populations and the distribution of the species have changed much. With changes in environment, rare species may become common; common and widespread species may become rare or extinct; species foreign to the area may enter, become established and affect the distribution of other forms.

Subspecies are groups of individuals with similar genetic components or are groups of microgeographic races. In instances where the phenotypic expression of these similar genetic factors, or the "characters," are, as a unit, uniformly different from those of animals of the same species in another geographic area, it is convenient to give recognition to the two kinds by separate subspecific name. Intergradation between two geographically adjacent subspecies occurs, directly or where impassable barriers separate them, indirectly by way of one or more other subspecies. Subspecies of mammals are geographic races, which means that to warrant recognition by subspecific name, there must be a logical geographic range in addition to morphological characters.

Timofeef-Ressovsky (1932, 1940) advances the theory of harmoniously stabilized gene-complexes to account for the persistence of subspecies. The persistence of subspecies as genetic units has been best explained, I feel, by Sumner (1932: 84-86) who theorizes as follows:

1. The number of young produced by a subspecies is greater than the
carrying capacity of the land they occupy, at least at certain
times or in some years.

2. Population pressure results, with a tendency of individuals to
emigrate outwards, to the border of the range of the subspecies,
where the population pressure is less.

3. The outward moving tendency keeps the center of the range of
the subspecies genetically "pure."

4. The peripheral wave continues, as long as favorable habitat is
encountered, until an oppositely directed wave of another race is
encountered.

5. Areas of intergradation represent local mingling of genetic
factors and do not affect the "pure" individuals of the central
part of the range of the subspecies.

Certain aspects of this hypothesis are strongly supported by the distribution of mammals in Washington. Witness the rapid invasion of _Citellus beecheyi_ and _Lepus californicus_ in Washington, and the eastern cottontail in western Washington and the domestic rabbit in the San Juan Islands. The volume of the "wave of population pressure" where no opposing force is met, is scarcely believable. In seven years the eastern cottontails released in southwestern Washington multiplied from a maximum of 12 individuals to a minimum of 40,000.

Competition between subspecies where their ranges come into contact seems to be exceptional. _Peromyscus maniculatus oreas_ and _P. m. austerus_ seem to afford an example of this. However, in a few cases subspecies seem to be determined in part by adaptation to restricted environments; each race lives only where local conditions favor its respective adaptations.

In the pocket gophers, where restricted habitat and fossorial habits cause numerous microgeographic races, these microgeographic races may be potential subspecies. This is especially true in the Puget Sound area, where six races occur in a small area. These races meet all the requirements of subspecies and are recognized as such. It should be pointed out, however, that these races and probably many other races produced by isolation, may represent degenerative mutations of the type mentioned by Wright (in Huxley, 1940). The principal differences of such races seem to have resulted from the loss of factors of original multiple factor series, with resultant homogeneity of the race. Inherent variability is another thing that has to be taken into account when considering the differentiation of the mammals of Washington into subspecies. The pocket gopher is an extremely plastic species, especially in Washington, whereas the Douglas squirrel is less so. The flying squirrels, the yellow-pine chipmunk and the snowshoe rabbit are the other plastic species. These species are not so likely to break up into numerous subspecies over all of their ranges as they are in Washington where in a small area the topography is highly varied. The range of the one subspecies, _Tamias amoenus amoenus_, to the southeast of Washington is larger than the combined ranges of all six races occurring in Washington but, so far as I can see, the topography and environment are no more varied in Washington than in the mentioned area to the southeast of it. The range of one subspecies, _Lepus americanus americanus_, in Canada is several times larger than the entire state of Washington, in which four races are found.

The shrews are poor subjects for a study of differentiation, principally because their small size makes it difficult to see morphological variations that may be present. The difficulty is increased because cranial sutures become ossified at an early age. Although it is difficult to evaluate the differentiation in them, there is some. The bats, especially the _Myotis_, are less restricted by geographic barriers than are terrestial mammals. Nevertheless, obvious differentiation exists. The larger predatory mammals and the artiodactyls are able to move over large areas, at least in the breeding season, but in these animals also, some differentiation has occurred.

The greatest changes, other than the extinctions, to occur in the mammalian fauna of Washington since the late Pleistocene, are changes in distribution. The interglacial cycle preceding the Vashon-Wisconsin glaciation was of far greater duration than the Recent. Presumably the mammalian fauna had, from a distributional standpoint, reached a relatively stable condition. The descent of the Vashon-Wisconsin ice destroyed the stability and set parts of the fauna in motion. Probably no stability was reached before the ice began to recede, and when it did so the previous movements of the various species were, at least in part, reversed. Stability has not yet been reached by the mammalian fauna of Washington. Great changes have occurred in historic times and other changes probably are under way at present.

In the following pages an attempt has been made to interpret the probable late Pleistocene and Recent distributional history of the species of mammals occurring in Washington. The interpretations are made in the light of what is known of the physical history of the state and are to be accepted as such rather than as evidence for the conclusions made concerning the physical history of the state of Washington and adjacent areas.

SCAPANUS TOWNSENDII.--Probably this animal was confined to the Humid Transition Life-zone of the Pacific Coast since the Pliocene.

SCAPANUS ORARIUS.--This species probably had a history similar to that of _townsendii_ up to the late Pleistocene. It seems slightly more adaptable than _townsendii_, and to be able to extend higher into the mountains. The distribution of the subspecies _orarius_ is almost exactly that of _S. townsendii_. In Oregon, _orarius_ extended eastward over the Cascades where the subspecies _schefferi_ developed. Perhaps this subspecies developed since the Pleistocene and since that time extended along the Columbia River Valley to southeastern Washington. The race _yakimensis_, in the Yakima Valley area, is closely related to _schefferi_, and seemingly could have been developed from a stock of _schefferi_ that migrated westward across the Simcoe Bridge.

NEUROTRICHUS GIBBSII.--The history of _Neurotrichus_ in North America was probably similar to that of the two species of _Scapanus_. It tolerates environmental differences to about the same degree that _Scapanus orarius_ does but occurs much farther south (Monterey County, California) than _S. orarius_. This may be because _Neurotrichus_ has no counterpart to compete with it in the south, whereas _Scapanus orarius_ must compete in northern California with the morphologically similar _Scapanus latimanus_. _S. orarius_ stops short at this place and _S. latimanus_ occupies all the territory to the south.

The shrew-mole of the lowland of Washington (_N. g. minor_) probably became distinct from the mountain subspecies (_gibbsii_) in Vashon-Wisconsin time.

SOREX CINEREUS.--It is reasonable to suppose that the cinereous shrew had a continuous range across the forested area of British Columbia in pre-Wisconsin time. Without having been isolated, the dark coastal race (_streatori_) may have developed from the wider-ranging inland _cinereus_, as a response to the denser, humid, coastal forest-habitat, after having been forced southward to Washington by the Vashon Glaciation. Since that time it is presumed to have reoccupied the coast of British Columbia and southern Alaska. This coastal race might have developed in Vashon time, while isolated in southwestern Washington. The Cascades are populated by a race of the Rocky Mountain Fauna, _S. c. cinereus_, which probably entered the Cascades from northeastern Washington or British Columbia in Recent Time. The absence of the species in western Oregon, its rarity in western Washington, and its abundance farther north suggest a northern origin and northward rather than southward postglacial movement. Had the full species _cinereus_ been a preglacial resident of western Washington we would expect _streatori_ or a race related to it to occur in the Cascades.

SOREX MERRIAMI.--The periphery of the range of this member of the Great Basin Fauna may have been in southeastern Washington since pre-Wisconsin time.

SOREX TROWBRIDGII.--This shrew is a typical Pacific coastal species with an extensive range along the Pacific Coast south of Washington. The Washington population may have been isolated in southwestern Washington during Vashon time or may have crossed the Columbia into Washington from western Oregon early in the Recent. Since the retreat of the ice it has extended northward to southern British Columbia and eastward to the eastern side of the Cascades. Save for crossing the Cascades its postglacial movements have been slight, as is typical of Pacific Coastal species. The race _destructioni_ probably has been isolated on Destruction Island for several thousand years.

SOREX VAGRANS.--This species probably has had a continuous range over the western United States since the late Pleistocene. The dark coastal race (_vagrans_) probably was differentiated from the paler races of the Great Basin in response to the more humid climate along the coast.

SOREX OBSCURUS.--The history of this shrew of alpine predilection probably corresponded closely to that of _Sorex cinereus_. The derivation of the dark, long-tailed, coastal race (_S. o. setosus_) from the smaller, paler, inland race (_obscurus_) probably occurred before Vashon-Wisconsin Time. _Sorex o. setosus_ is one of a complex of races distributed along the Pacific Coast from Alaska to California.

SOREX PALUSTRIS.--This species has a wide range in North America and extends southward in the Cascade-Sierra Nevada Chain to southern California. Its extensive range at present in this mountain chain suggests that it was resident in the Cascades previous to Wisconsin time. Mountain water shrews probably reached the Olympic Mountains from the Cascades by way of the Puget Bridge in early Recent Time.

SOREX BENDIRII.--This Pacific Coastal species probably had a history very similar to that of _Neurotrichus_ and _Scapanus orarius_.

The difference between the Bendire water shrews of western Washington and western Oregon indicates that the Washington population was separated from the shrews of western Oregon during Vashon Time. The white-bellied race of the Olympic Peninsula is probably of local origin.

MICROSOREX HOYI.--The Washington record of this shrew at Loon Lake, Stevens County, is in an area where mammals typical of the Rocky Mountain Fauna occur.

MYOTIS LUCIFUGUS.--The dark race of this species (_alascensis_) may have persisted through the glacial period in southwestern Washington. The race _carissima_, of the Great Basin Fauna, may have entered the state since the glacial period, from the south, of course. Habitat selection determines their range at present.

MYOTIS YUMANENSIS.--The dark, coastal race (_saturatus_) seems to be an established member of the Pacific Coastal Fauna. Unlike _lucifugus_, the coastal race is not found east of the Cascades. The race _sociabilis_, of the Great Basin, has doubtless entered the desert of eastern Washington from eastern Oregon.

MYOTIS KEENII.--The southernmost record station for this north coastal species is on the Olympic Peninsula of Washington. It probably developed in the humid, northern part of the Pacific Coastal area previous to the last Pleistocene glaciation and extended its range to the south in Vashon-Wisconsin Time. The range of tolerance in _M. k. keenii_ seems to be more restricted than that of _M. lucifugus alascensis_.

MYOTIS EVOTIS.--In Washington, the distribution of this bat is similar to that of _Myotis lucifugus_. The dark, forest race probably originated in the north-coastal region. The paler race, that developed in the southwest, entered eastern Washington from Oregon.

MYOTIS THYSANODES.--In Washington this species has been recorded only in the southeastern part where the Great Basin Fauna occurs. It probably originated in the southwestern United States, and a point in British Columbia a little way north of Washington marks the northern edge of its natural range.

MYOTIS VOLANS and MYOTIS CALIFORNICUS.--Remarks made about _Myotis lucifugus_ apply also to these two species.

MYOTIS SUBULATUS.--The northwestern periphery of the range of this species seems to be in eastern Washington.

LASIONYCTERIS NOCTIVAGANS.--Undifferentiated subspecifically from coast to coast, no basis is provided for judging the route by which this species entered the state.

PIPISTRELLUS HESPERUS.--The northwestern periphery of the range of this bat, also, lies in eastern Washington.

EPTESICUS FUSCUS.--Big brown bats from both eastern and western Washington seem to have been derived from the Pacific Coastal race of the species. Presumably it extended its range westward across the Cascades in early post-Pleistocene Time.

LASIURUS CINEREUS.--No speculation as to the distributional history of the hoary bat seems justified at present.

CORYNORHINUS RAFINESQUII.--The dark, coastal race of this bat probably persisted in southwestern Washington and western Oregon through Vashon Time and moved northward in the Recent. The paler _intermedius_ probably invaded eastern Washington from eastern Oregon in the Recent.

ANTROZOUS PALLIDUS.--This species strays into eastern Washington from Oregon as part of the Great Basin Fauna.

URSUS AMERICANUS.--The dark, western race of the black bear (_altifrontalis_) and the paler, inland race (_cinnamomum_) were probably separated by a glacial divergence. The inland race has entered northeastern Washington in the Recent with other members of the Rocky Mountain Fauna.

URSUS CHELAN, etc.--The apparent past distribution of _chelan_ indicates it to have invaded Washington from British Columbia since the Pleistocene.

The apparent absence of grizzly bears from the southern Cascades and western Washington may indicate their absence from these areas immediately before pre-Vashon time, or their extermination in or shortly after that period.

PROCYON LOTOR.--The raccoon of western Washington seems to be the Pacific Coastal race which occurs also in western Oregon and northwestern California. This indicates that the coastal race (_psora_) was confined to the coastal area south of Washington during Vashon Time and has only recently reinvaded western Washington. It is possible, though less likely, that raccoons existed in southwestern Washington during Vashon Time but did not develop racial characters, or that the Columbia was crossed so frequently that genetic differences were dispersed throughout the entire population.

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.

In immediate pre-Vashon-Wisconsin Time, the dark race _streatori_ probably occurred in western Washington. The race _murica_ probably occurred in the Blue Mountains then, as it does today, but probably occurred also in the Cascades of Washington. The descent of the Vashon glaciers probably displaced _streatori_ from the northern part of its range, at least temporarily. In the Cascades, _murica_ was likewise forced southward. Ermines related to the northern _richardsonii_ were forced into northern Washington and Idaho by the Wisconsin ice. They probably were unable to live on the barren, unglaciated plains of eastern Washington but persisted in Idaho.

The ranges of the three forms at the maximum extent of the Vashon-Wisconsin may be reconstructed as follows: _streatori_ in southwestern Washington; _murica_ in the southern Cascades and the Blue Mountains; _invicta_ stock in northern Idaho. While so isolated, the ermines of the southern Cascades probably mingled, to a certain extent, with _streatori_ and developed the characters that now separate _gulosa_ from both _murica_ and _streatori_. The intermediate nature of _gulosa_ has been mentioned by Hall (1945: 85).

The retreat of the ice allowed _streatori_ to move north and _invicta_ to move north and east into Washington and the northeastern Cascades. To a lesser extent, _gulosa_ may have moved north. The poorly-marked race _olympica_ probably evolved from _streatori_ in the Recent. It is difficult to account for the dark race _fallenda_.

It must have evolved from _streatori_ in the Recent but the origin of such a strongly marked race in such a short time is surprising. It might be mentioned that a similarly differentiated race of chipmunk, _Eutamias amoenus felix_, occupies much the same range.

MUSTELA FRENATA.--The long-tailed weasels of the Pacific Coast behave as a plastic group and clearly show the effect of the Vashon-Wisconsin Divergence. The range of the coastal race, _altifrontalis_, indicates that it was isolated in southwestern Washington during Vashon Time. In that period, or shortly after, it extended its range southward but only along the extreme, coastal area of Oregon (see Hall, 1936: 101). Following the retreat of the ice it extended its range northward to the deglaciated area of western Washington.

Also following the retreat of the ice, a Great Basin subspecies (_nevadensis_) extended its range northward. This race seems to have been more adaptable and successful than other kinds of Great Basin mammals, for it extended its range farther northward, eastward and westward than most.

A third race, _washingtoni_, was isolated in the southern Cascade Mountains during Vashon Time and became differentiated from both _altifrontalis_ and _nevadensis_. It is now found in the Cascades from central Oregon north to Mount Rainier. It is difficult to see why it did not extend its range to include the northern Cascades when the glacial ice left, but it did not. Instead _altifrontalis_ entered the northern Cascades from the west and _nevadensis_ did the same from the east. Weasels obtained in habitats north of Mt. Rainier are intergrades between _altifrontalis_ and _nevadensis_.

One is reminded here of the _douglasii_ group of _Thomomys talpoides_ in which subspecies did not move north of Mt. Rainier in postglacial time. The area north of Mt. Rainier was populated instead by gophers of the _fuscus_ group, subspecies of which invaded the area from the east. Perhaps Mt. Rainier itself served as a barrier to alpine mammals in the immediate post-Pleistocene. Perhaps _Mustela f. washingtoni_ will eventually extend its range northward, displacing the _altifrontalis-nevadensis_ intergrades from the habitats to which _washingtoni_ may be better adapted.

The Blue Mountains of southeastern Washington are occupied by a weasel (_effera_) that has a more extensive range in eastern Oregon. The range of this race has probably not changed materially for a long period of time.

One would expect the weasels from extreme northeastern Washington to be referable to the race _oribasa_, of the Rocky Mountain Fauna. Instead they are intermediate between that race and the Great Basin race, _nevadensis_. Apparently _nevadensis_ was so dynamic and adaptable that it actually entered the geographic ranges of surrounding races for some distance. In view of Sumner's theory for the retention of subspecies, one might say that the population pressure of _nevadensis_ on the periphery of its range is stronger than the opposing pressure of some surrounding races.

MUSTELA VISON.--Pending a review of the minks of North America, little can be said concerning their historical distribution in the state of Washington. From the general range of the species in western North America, one would expect some effect of the Vashon-Wisconsin Divergence to be apparent. There is some evidence for this. Minks from Idaho and adjacent parts of British Columbia are distinctly less reddish than minks from the area about Puget Sound, as noted by Davis (1939: 138).

GULO LUSCUS.--The range of the subspecies _luteus_, peculiar to the Cascades and Sierra Nevada suggest that the wolverine may have been forced southward in the Cascades and there isolated during Vashon Time. The differences separating the southern race from the northern may have been developed while the two populations were isolated. The range of the wolverine was probably more extensive in glacial and immediate postglacial time than at present.

LUTRA CANADENSIS.--The otter of western Washington seems to be a member of the Pacific Coastal Fauna. Little can be said regarding the distributional history of the species in the state, for specimens from eastern Washington are not numerous enough to permit of a person certainly establishing their systematic position.

SPILOGALE GRACILIS.--The western race of the civet cat (_latifrons_) seems to be a coastal race, isolated in southwestern Washington and western Oregon during Vashon time. The eastern race, _saxatilis_, is a race of the Great Basin Fauna, that has entered the state from Oregon and that will probably extend its range to the north.

MEPHITIS MEPHITIS.--Of the four subspecies of skunks occurring in Washington, two seem to have been resident in the state during Vashon Time. The western race, _spissigrada_, was probably isolated in southwestern Washington and extended its range northward, in the deglaciated area of western Washington, after the retreat of the ice. Another race (_notata_) was probably isolated in the southeastern Cascades and adjacent Oregon. _M. m. hudsonica_ of the Rocky Mountain Fauna entered the northeastern part of Washington after the ice retreated from there. A race of the Great Basin Fauna, _major_, entered southeastern Washington from Oregon and may eventually extend its range farther north.

It is interesting to note that both of the western races, _spissigrada_ and _notata_, both of which probably developed in Washington during Vashon Time, occupy limited ranges in adjacent Oregon (Bailey, 1936: 308).

TAXIDEA TAXUS.--This species has probably long been resident on the Columbian Plateau and in southeastern Washington. For the early distributional history of the species see Hall (1944: 17). Pleistocene remains, referable to this race, have been found in Franklin County.

VULPES FULVA.--The red fox of the Cascades was probably isolated there during Vashon Time by glacial ice. Its range extends southward in the Cascades to Oregon. The fox of eastern Washington is probably a member of the Rocky Mountain Fauna that lived in the Blue Mountains of southeastern Washington in Wisconsin Time and that emigrated to northeastern Washington in Recent Time.

CANIS LATRANS.--The distributional history of the coyote in Washington is not clear.

CANIS LUPUS.--The dark wolf (_fuscus_) of western Washington is probably a coastal race. The race that may have occurred in northeastern Washington probably was an invader from the Rocky Mountain Fauna, and the race that possibly occurred in southeastern Washington would be assumed to have long been a resident of the area.

FELIS CONCOLOR.--The cougar of western Washington is a coastal race, probably developed while isolated in southwestern Washington and western Oregon. The cougar of northeastern Washington probably entered the state with other Rocky Mountain species, early in the Recent. The cougar of the Blue Mountains of southeastern Washington has probably long been resident there.

LYNX RUFUS.--The bobcat of western Washington seems to be a coastal race that was isolated in either southwestern Washington or western Oregon by Vashon ice. It has since extended its range into southern British Columbia. The bobcat of eastern Washington seems to be a member of the Great Basin Fauna that has spread to some forested areas on the periphery of the more arid life-zones.

LYNX CANADENSIS.--The lynx is an element of a northern fauna that was probably forced southward into the Cascades and Rocky Mountains. Its range was probably more extensive, as is indicated by the scattered records of its occurrence in Oregon (Bailey, 1936:271).

MARMOTA MONAX.--The woodchuck invaded northeastern Washington in the early Recent with the Rocky Mountain Fauna.

MARMOTA FLAVIVENTRIS.--The yellow-bellied marmot is a typical member of the faunas of the Great Basin and the southern Rocky Mountains. It has doubtless entered southeastern Washington from eastern Oregon at an early time. In northeastern Washington, west of the Columbia River, it occupies alpine habitat, but it does not occur farther east, where _Marmota monax_ is found, or in the Cascades where _Marmota caligata_ lives.

The yellow-bellied marmots are great wanderers, and commonly are found in scattered outcrops far out on the Columbian Plateau. There is even one record for western Washington, near Bellingham, Whatcom County. This individual must have crossed some low pass in the Cascades from the area about Lake Chelan. There are records of eastern Washington birds occurring in this same area, so it seems likely that the marmot was a natural stray and not an animal that escaped from captivity.

MARMOTA CALIGATA.--The absence of the hoary marmot from the Cascades of Oregon, and the presence there of _Marmota flaviventris_, indicates that the species did not occur in the southern Cascades of Washington during Vashon Time. Presumably the hoary marmot is a member of the fauna of the northern Rocky Mountains and entered the Cascades of Washington in the Recent, after which it spread widely and rapidly owing to lack of competition with any established species of marmot.

MARMOTA OLYMPUS.--This species has probably lived in the Olympic Mountains since pre-Vashon Time.

CITELLUS WASHINGTONI.--This ground squirrel has probably lived on the Columbian Plateau since before Wisconsin Time.

CITELLUS TOWNSENDII.--The Townsend ground squirrel probably entered the Yakima Valley area from Oregon. The differences between it and its relatives in Oregon indicate a considerable period of isolation but one far shorter than the period during which _washingtoni_ is presumed to have been isolated from _townsendii_.

CITELLUS COLUMBIANUS.--The Columbian ground squirrel might have been forced southward in the Rocky Mountain area by the Wisconsin glaciation, might have lived in southeastern Washington since then, and might have invaded northeastern Washington in the Recent with other species of the Rocky Mountain Fauna.

CITELLUS BEECHEYI.--This ground squirrel is known to have entered Washington about 1915 from Oregon.

CITELLUS SATURATUS.--The mantled ground squirrel of the Cascades probably evolved, from the _lateralis_ stock, as a separate species while isolated in the southern Cascades during Vashon Time. It is a poorly differentiated species and may actually be instead a strongly marked subspecies.

CITELLUS LATERALIS.--The golden-mantled ground squirrels of northeastern and southeastern Washington are closely similar. It is deduced that _connectens_ of southeastern Washington developed the differences that characterize it while isolated, from the main stock, in the Blue Mountains area of Washington and Oregon.

The race found in extreme northeastern Washington (_tescorum_) probably reached that area in relatively recent times. Its range in Washington is more restricted than that of several other members of the Rocky Mountain Fauna; areas of suitable habitat west of the Columbia River are not inhabited by these ground squirrels. Its range in Washington is almost exactly that of (_Marmota monax_).

TAMIAS MINIMUS.--The least chipmunk of the Yakima Valley is the same race (_scrutator_) as that occupying the Great Basin area of Oregon and Nevada. It must have crossed the Columbia in relatively recent times. Had it been resident in the isolated Yakima Valley area for any considerable period of time, the development of distinctive racial characters there would be expected. Perhaps, then, it has not been resident there as long as has the Townsend ground squirrel which, though closely related to the ground squirrel of eastern Oregon, is racially distinct.

The least chipmunk of the Columbian Plateau is thought to be racially distinct from its relatives in the Yakima Valley and eastern Oregon. Probably it reached the Plateau very early in the Recent. It has probably not been separated from the parent stock as long as has the ground squirrel (_Citellus washingtoni_) of the plateau. The ground squirrel is specifically rather than racially distinct.

TAMIAS AMOENUS.--The distributional picture of the yellow pine chipmunks in Washington is complex. (Fig. 81.) Certain habits of these mammals doubtless have modified what was probably the original postglacial distribution of the species. Chipmunks are diurnal and natural selective factors for color possibly operate more strongly on animals active by day than on nocturnal animals. Yellow pine chipmunks are neither forest nor desert inhabitants. Indeed, dense forests or open deserts serve as barriers to their distribution. They prefer brush lands, open woods, and other habitats where there is food and cover but abundant sunlight. In such habitats they are almost independent of altitude, temperature and humidity. They live in the Olympic Mountains where rainfall is heavy and humidity high. They live and breed at considerable altitudes in the Cascades, even in the crater of Mount Rainier, where snow, ice and freezing conditions exist the year around. On the other extreme, they occupy the low, open pine forests and brush lands at the lower edge of the Arid Transition Life-zone where temperatures, in summer, are high and rainfall scarce.

We find in the present distribution of the species in the Cascade-Sierra Nevada chain and the Rocky Mountains, indication that the species had a wide geographic range over western North America previous to the Vashon-Wisconsin glacial interval. Probably the range of the species extended in an arc, from the Rocky Mountains across northern Washington to the Cascades, around the basaltic plateau desert in eastern Washington and Oregon. Presumably the descent of the Vashon-Wisconsin glaciers broke this arc into two parallel geographic ranges, the Rocky Mountains and the Cascade-Sierra Nevada chain, with a desert area between.

Almost every species of forest-dwelling animal had its range separated into two parts by the southward movement of the glaciers. Most of these forest-dwelling species were composed of relatively homogeneous stocks, although the yellow pine chipmunk probably was not. The extensive range of tolerance of the yellow pine chipmunk to altitude and climate and its unique habitat requirements cause it to meet radically different natural selective factors. The predators of the chipmunks near Wenatchee, Chelan County, would include: rattlesnake, gopher snake, badger, striped skunk, prairie falcon, red-tailed hawk and other predominantly desert-dwelling species. The chipmunks at Stevens Pass, in the mountains to the west, would have to contend with: marten, black bear, goshawk, bald eagle and other alpine predators. At the present time, the chipmunk of the eastern Cascades is racially distinct from that of the higher Cascades. Geologic and botanical evidence indicates that the Columbian Plateau was a desert in pre-Wisconsin Time. We suppose that a transition from alpine conditions in the Cascades to desert conditions on the Columbian Plateau existed even in pre-Wisconsin Times. We suppose also that the chipmunk existed in this transition area and in the Cascades before Wisconsin Time and in the southern and southeastern Cascades during Wisconsin Time. We further suppose that the differences separating the transition area race (_Tamias amoenus affinis_) from the mountain race (_T. a. ludibundus_) came about through natural selection and not as a result of geographic isolation. The principal difference between the two is the paler color of the race in the transition area.

The descent of the Vashon-Wisconsin glaciers, then, found two races of the yellow pine chipmunk in the Cascades. Chipmunks living north of the Columbian Plateau, in northern Washington and British Columbia, were probably forced southward onto the inhospitable plains of the plateau and exterminated. Farther east, north of northeastern Washington, chipmunks from the north were probably forced southward to compete with resident chipmunks.

The range of _Tamias amoenus luteiventris_ in Washington, Idaho and Montana is most unusual (See Howell, 1929; Davis, 1939). From a compact range in Montana, two long fingers reach northward and westward. The western finger crosses Idaho to end in the Blue Mountains of Oregon and Washington. The northern finger crosses northern Idaho, northeastern Washington and extends on into southern British Columbia. Between these two fingers of the range of _luteiventris_ another race (_canicaudus_) is found. This race occupies a more lowland area than does _luteiventris_. The range of _luteiventris_ in the northern Rocky Mountains is extensive. Presumably this race occupied an area farther north in pre-Wisconsin Time and was forced southward to its present range by the Wisconsin glaciers. The original population occupying extreme eastern Washington and adjacent Idaho was _Tamias amoenus canicaudus_. The pre-Wisconsin range of this race might have been more extensive. At any rate, _luteiventris_ which was driven southward displaced _canicaudus_, or some other race of chipmunk, from much of the Rocky Mountains south of the glacier. The northern chipmunks were adapted to more boreal conditions and perhaps otherwise better suited to environmental conditions of the northern Rocky Mountains. A small population of the older established race (_canicaudus_) persisted in lowland areas of eastern Washington and adjacent Idaho.

Regarding the range of _canicaudus_, surrounded by the range of _luteiventris_ on three sides and faced by desert on the west, Davis (1939: 220) writes, "It may be that, of these two races, _luteiventris_ has a greater range of tolerance to environmental conditions and, thus, is able to succeed in areas to which _canicaudus_ is not adapted. This inference is supported by the fact that _luteiventris_ occupies a large range which is diversified geographically and climatically, whereas _canicaudus_ seems to be limited to a much smaller, more nearly uniform area." Seemingly _canicaudus_ now exists only in an area ideally suited to it, and one where it can successfully compete with the generally more adaptable and successful _luteiventris_. The maximum extent of the glacial ice, then, found _luteiventris_ the dominant chipmunk in the northern Rocky Mountains, with an isolated population of _canicaudus_ in eastern Washington and adjacent Idaho.

The topography of the ground moraine exposed by the retreat of the Vashon-Wisconsin glaciers was a barrier to many species of mammals. The rough, rocky surface with thin soil probably first supported mosses and grasses, then brush, and later trees. The earlier stages of plant succession on the deglaciated ground probably presented ideal habitat for yellow pine chipmunks. Certainly the races immediately adjacent to the glaciers extended their ranges farther north than many species. In eastern Washington, _T. a. luteiventris_ spread to the northeastern corner of the state and on into British Columbia. In the northern Cascades, _T. a. affinis_ spread northward and eastward, across the Okanogan River, into northeastern Washington as far as the range of _luteiventris_. The chipmunk of the higher Cascades (_ludibundus_) likewise extended its range northward into British Columbia. In the northwestern Cascades of northern Washington and southern British Columbia, a richly-colored race, _T. a. felix_, now occupies a limited geographic range. This race doubtless originated from _ludibundus_ stock but the method of its development is unknown. Perhaps in early postglacial time, selective factors developed in chipmunks of the western slopes of the Cascade Mountains the rich, dark color of _felix_. The ancestral _ludibundus_ may have given rise to a pale race, _affinis_, in the arid eastern Cascades and a dark race, _felix_, on the humid western slope of the Cascades. This seems improbable for there is no trend to darker color on the western border of the range of _ludibundus_ south of the range of _felix_, and instead, _affinis_ may have given rise to _ludibundus_. A more appealing hypothesis is that a local mutation in some _ludibundus_ stock so changed the range of tolerance of a portion of the population that it was allowed to enter the more dense habitat along the coast north of the Fraser River and, there, isolated by habitat selection, it developed the characters of _felix_. Population pressure later forced it eastward until the eastern border of its range again met the range of the ancestral race, _ludibundus_.

The chipmunks of the Olympic Mountains probably reached their present range from the Cascades. Their probable path of emigration was westward from Mt. Rainier, along the glacial outwash train of Nisqualli Glacier, to the moraine and outwash apron of the Vashon Glacier and thence to the Olympics. So similar are the chipmunks of Mt. Rainier and the Olympic Mountains that Howell (1929) included Mt. Rainier in the range of _caurinus_.

Briefly summarized, the probable pre-Vashon-Wisconsin distribution of chipmunks of the species _Tamias amoenus_ in Washington was: _ludibundus_ in the higher Cascades; _affinis_ in the eastern Cascades; _canicaudus_ in eastern Washington and adjacent Idaho; and _luteiventris_ in the area north of the range of _canicaudus_. The descent of the Vashon-Wisconsin ice restricted but did not materially alter the ranges of _ludibundus_ or _affinis_. On the east, _luteiventris_ was forced southward to compete with _canicaudus_ and displaced it over a large region, especially in mountainous areas. Following the retreat of the ice, _luteiventris_, _affinis_, and _ludibundus_ extended their ranges northward over the deglaciated territory. A stock of _ludibundus_ that moved westward from Mt. Rainier became isolated and gave rise to _caurinus_. In some less obvious development, _ludibundus_ stock gave rise to _felix_ north of the Fraser River in the Cascades.

TAMIAS RUFICAUDUS.--Until a better understanding of the range of this chipmunk and its relation to other _Tamias_ is gained, uncertainty will remain concerning its distribution in the past.

TAMIAS TOWNSENDII.--This is a typical coastal species that ranges southward, along the coast, to California. The lowland race of western Oregon and Washington (_townsendii_) probably occurred no farther north than southwestern Washington when the Vashon Glacier was in place. Chipmunks of this species in the Cascades and in the southern Olympic Mountains probably developed independently the slightly paler color that separates _cooperi_ from _townsendii_. The tendency for species of the Pacific Coastal Fauna of the Cascades and the Olympic Mountains to be paler than their lowland relatives is widespread.

After the retreat of the ice, both races probably moved northward. Perhaps because of its alpine adaptations, _cooperi_ has moved farther than _townsendii_. Also, _townsendii_, in the lowlands, ranges to the Fraser River, a barrier not encountered by _cooperi_.

SCIURUS GRISEUS.--This species of the Pacific Coastal Fauna probably entered Washington from Oregon since the retreat of the Vashon Glacier. It has probably entered the state in relatively recent times.

TAMIASCIURUS HUDSONICUS.--The two species of red squirrels, _T. hudsonicus_ and _T. douglasii_, are specifically distinct and probably became differentiated in the Pleistocene when southward moving glaciers cut in two the range of the ancestral stock. The morphological differences are too great, comparatively, to have occurred during the Vashon-Wisconsin Divergence. _T. hudsonicus_ probably occupied a range in pre-Wisconsin Time that included the Rocky Mountains and areas to the north. Glacial ice probably restricted the range of _hudsonicus_ in Wisconsin Time but after the retreat of the ice _hudsonicus_ moved northward to reoccupy its former range. It also moved westward across northern Washington to the Cascades, where it met the range of _douglasii_. Farther north, it moved westward to the Pacific, thus occupying an area that, in pre-Vashon time, probably was occupied by _douglasii_.

TAMIASCIURUS DOUGLASII.--The Douglas squirrel probably occupied the coastal region of Oregon, Washington and British Columbia in pre-Vashon Time. The descent of the ice restricted its range to southwestern Washington and areas to the south. After the retreat of the ice it moved northward somewhat but, like other coastal species, the movement was slow. Meanwhile _hudsonicus_ from the Rocky Mountain Fauna, had spread to the coast of British Columbia.

GLAUCOMYS SABRINUS.--This flying squirrel is a plastic species. It inhabits all of the forested parts of Washington. The distributional picture presented by the 5 races (Fig. 92) which occur in Washington is complicated. The ranges of 3 of these lie principally outside the state of Washington.

The race _oregonensis_ occupies Washington and Oregon west of the Cascades; _fuliginosus_ occupies the Cascades of Washington, Oregon and southern British Columbia; _columbiensis_ occupies the interior valleys of British Columbia and adjoining Washington; _latipes_ occupies the northern Rocky Mountains of British Columbia, northern Idaho and extreme northeastern Washington; and _bangsi_ occupies the Blue Mountains of Washington and Oregon and a wide range in Idaho and eastward.

The differences separating the race _oregonensis_ from other subspecies found in Washington are relatively great. This lowland race is smaller and richer in color. The other races exhibit slight but relatively constant differences. The relatively great difference between _oregonensis_ and the other races indicates that _oregonensis_ was isolated from the remainder of the species for a considerable time. Presumably _oregonensis_ was a strongly differentiated coastal race in pre-Vashon Time and occupied most of western Washington and Oregon. The descent of the Vashon ice restricted the range of _oregonensis_ to southwestern Washington and western Oregon. The descent of the ice forced a northern race, _fuliginosus_, southward into the range of _oregonensis_. The northern race, adapted to boreal conditions, was able to compete successfully with the established _oregonensis_ only in mountainous areas. In the Cascade Mountains, _fuliginosus_ extended its range southward to southern Oregon.

The descent of the Wisconsin ice in eastern Washington forced the flying squirrels of adjacent British Columbia southward into the Rocky Mountains. These squirrels were probably closely related to _fuliginosus_, or to _bangsi_, which latter race already may have been established farther south in the Rocky Mountains. The Blue Mountains of southeastern Washington were probably inhabited by _bangsi_ in Wisconsin times, or even earlier. The retreat of the Vashon-Wisconsin glaciers allowed the flying squirrels to extend their ranges northward. In western Washington _oregonensis_ moved to southern British Columbia. In the Cascade Mountains the more boreal _fuliginosus_ moved much farther northward and, north of the Okanogan Valley, spread eastward to the arid, interior valleys of British Columbia. Subsequent differentiation in the population of the arid, interior valleys developed the slightly differentiated race _columbiensis_. Farther east, flying squirrels from the northern Rocky Mountains moved northward. Northeastern Washington and adjacent British Columbia were occupied by _latipes_, derived from _bangsi_.

THOMOMYS TALPOIDES.--Views as to the probable historical distribution of this plastic group have been presented in an earlier report (Dalquest and Scheffer, 1944: 308-333). This may be briefly summarized as follows.

Previous to Vashon-Wisconsin Times, pocket gophers occupied at least the Cascade Mountains and the Columbian Plateau of Washington. The race occupying the Columbian Plateau, _devexus_, was probably racially distinct in pre-Wisconsin time. The descent of the Vashon-Wisconsin glaciers isolated gophers in the southern Cascades. Three racial stocks developed there: _shawi_ in the Mount Rainier area; _limosus_ in the Columbia River Valley south of the Cascades; and _immunis_ in the mountainous area between the other two races. At the maximum extent of the Wisconsin ice, gophers from the Columbia River Valley (_limosus_) were able to cross the Simcoe Bridge and reach the Blue Mountains. With the retreat of the Wisconsin ice, the Simcoe Bridge was closed. Gophers isolated in the Blue Mountains developed the racial characters of _acqualidens_ and those between the Blue Mountains and the Columbia River intergraded with the desert race, _devexus_. These intergrades, which have, also, some characters of their own, bear the name _columbianus_. Gophers in the southern Cascades (_limosus_) moved westward on prairie-like river terraces to Clark County where, isolated, they became racially distinct (_douglasii_).

Gophers from the Mount Rainier area (_shawi_) moved westward on glacial outwash trains to the extensive outwash aprons of the Vashon glaciers in the area about Puget Sound. Here they multiplied and spread to the Olympic Mountains. Growth of forest on the original outwash apron broke the area into numerous isolated prairies. Gophers in the Olympic Mountains (_melanops_) were isolated from those in the area about Puget Sound. Six distinct races originated on the isolated prairie (_glacialis_, _tacomensis_, _pugetensis_, _yelmensis_, _tumuli_, _couchi_).

Following the retreat of the glacial ice from eastern Washington, pocket gophers from the Blue Mountains of Oregon (_wallowa_) moved northward into Washington and gophers from the Rocky Mountain Fauna of Idaho moved onto the deglaciated part of northeastern Washington. From northeastern Washington they spread westward to the Cascades and thence southward to meet the native gophers of the Cascades in the Yakima Valley Area. No racial differentiation in these gophers occurred; all are referable to _fuscus_. Where _fuscus_ and the native gophers came together in the Yakima Valley, a new race, _yakimensis_, developed.

PEROGNATHUS PARVUS.--Three races of the pocket mouse occur in Washington. Two of these (_lordi_ and _columbianus_) occur on the Columbian Plateau. Like many desert species that occur on the Columbian Plateau, the pocket mice are rather different than their relatives in eastern Oregon. Presumably they have been isolated on the plateau since before Vashon-Wisconsin Times.

The range of the pocket mouse of southeastern Washington, _Perognathus parvus parvus_, is continuous with the range of the race in Oregon. This same race occurs in the Yakima Valley, whence it probably arrived from Oregon in relatively recent time.

The distribution of pocket mice on the Columbian Plateau, in eastern Oregon and in the Yakima Valley resembles that of the least chipmunk in those areas. It is also similar to, but of more recent origin than, that of the ground squirrels, _Citellus washingtoni_, and _townsendii_.

DIPODOMYS ORDII.--This kangaroo rat enters the desert area of southeastern Washington from Oregon. It may be expected eventually to cross the Columbia River to the Yakima Valley and the Snake River to the Columbian Plateau.

CASTOR CANADENSIS.--Two races of beavers occur in Washington. One, found in southwestern Washington and northwestern Oregon, is dark with a short, wide skull. The other, ranging over most of the state, is paler with a longer, narrower skull.

The form now found in southwestern Washington and adjacent Oregon (_idoneus_) was probably isolated there by the Vashon glaciation and developed its characters while isolated. The other race, _leucodonta_, was probably widely spread in Wisconsin Time. Beavers are present in Moses Lake, in almost the center of the Columbian Plateau. Beavers might well have lived in the streams of melt water that emerged from the Wisconsin Glacier. The beavers of western Washington, save those in the extreme southwest, are like the beavers of eastern Washington. It seems likely that the race _leucodonta_ originated north of the state of Washington and was forced southward by the Vashon-Wisconsin glaciers. This northern race, adapted to boreal conditions, competed with the resident coastal race, _idoneus_, and occupied much of its range. The distribution of the races of muskrat in Washington closely resembles that of the beavers.

ONYCHOMYS LEUCOGASTER.--The desert-dwelling grasshopper mouse has doubtless entered eastern Washington and the Yakima Valley from eastern Oregon at a relatively recent time.

REITHRODONTOMYS MEGALOTIS.--The harvest mouse, like the grasshopper mouse, seems to have entered Washington from Oregon at a relatively recent date. Within the last ten years it has extended its range into the Okanogan Valley in British Columbia.

PEROMYSCUS MANICULATUS.--Six subspecies of _Peromyscus maniculatus_ occur in the state of Washington. The geographic range of one of these (_rubidus_) lies mainly in the states of California and Oregon and includes, so far as is known, a single small island in the Columbia River that is politically within the state of Washington. Another (_hollisteri_) is restricted to certain islands in northern Puget Sound and obviously has become subspecifically differentiated in postglacial time. The remaining four subspecies, namely _oreas_, _austerus_, _artemisiae_ and _gambelii_, have extensive geographic ranges. These subspecies are not confined to their geographic ranges by geographic barriers. Deer mice occur in the deep forests and the open desert, on high mountains and in low valleys, and are almost everywhere the commonest species of mammal present.