1911. Evotomys phaeus Swarth, Univ. California Publ. Zool., 7:127, January 12, type from Marten Arm, Boca de Quadra, Alaska.
When Swarth (loc. cit.) named the red-backed mouse of the mainland of southern Alaska as a new subspecies, he characterized it as "Size rather large. Differs from E. [= Clethrionomys] wrangeli, nearest it geographically, in cranial characters and in much longer tail; from E. caurinus, the species to the southward in British Columbia, in larger size and longer tail." He remarked (loc. cit.): "I had supposed that the red-backed mouse occurring on the mainland coast of this region would prove to be E. wrangeli, but the latter appears to be purely an insular species. I have had no specimens of that race for comparison, but the Evotomys secured differ so widely from it in all the essential peculiarities of the species as given in the published descriptions that there seems little doubt of their belonging to a different species. Wrangeli has a short tail, less than twice as long as the hind foot—in adults of phaeus the tail is invariably more than twice the length of the foot, frequently more than a third of the entire length of the animal."
The external and cranial measurements of two subadults in the United States National Museum (No. 217413 from Quadra Lake and No. 217415 from Marten Arm, Boca de Quadra, taken in mid-February) and three old adults from Fort [= Port] Simpson, British Columbia (Nos. 90263-90264, 90272 USBS), are almost the same as those given by Swarth in the original description of Clethrionomys phaeus.
In cranial measurements, as well as in the structure of the palate and last upper molar, C. phaeus agrees with the gapperi group (to which it has been assigned by Davis, The Recent Mammals of Idaho, The Caxton Printers, p. 306, April 5, 1939, and by Orr, Jour. Mamm., 26:69, February 12, 1945) and differs from Clethrionomys occidentalis caurinus (which was assigned above to the occidentalis group, formerly the californicus group).
Since the measurements of specimens examined by us, as well as those recorded by Swarth (op. cit.), fall within the range of those of the species Clethrionomys gapperi, and since the differences between phaeus and C. g. saturatus are of the kind and degree that separate subspecies in C. gapperi we employ the name combination Clethrionomys gapperi phaeus (Swarth). C. g. saturatus, as understood by us, occurs to the southeast of C. g. phaeus in the Rocky Mountains of British Columbia, and in northeastern Washington, northern Idaho and northwestern Montana.
Specimens examined.—Total, 23, distributed as follows: Alaska: Chickamin River (Behm Canal), 15 (MVZ); Boca de Quadra, 3 (MVZ); Marten Arm, Boca de Quadra, 1 (USNM); Quadra Lake, 1 (USNM). British Columbia: Fort [= Port] Simpson, 3 (USBS).
Clethrionomys gapperi wrangeli (Bailey)
1897. Evotomys wrangeli Bailey, Proc. Biol. Soc. Washington, 11:120, May 13, type from Wrangell, Wrangell Island, Alaska.
When Bailey (loc. cit.) named the red-backed mouse from Wrangell Island, Alaska, he characterized it as "A large, dull-colored species entirely distinct from any known form," and remarked: "In no way does E. [= Clethrionomys] wrangeli show a close relationship to any other American species. In size and relative proportions it comes closest to E. dawsoni, from which it differs widely in coloration and more widely in cranial characters. With the long-tailed species south and east of its range there is no need of comparison."
Swarth (Univ. California Publ. Zool., 24:173, June 17, 1922) reported that three specimens from Flood Glacier and 23 from Great Glacier, British Columbia, and four from Sergief Island, at the mouth of the Stikine River, Alaska, were: "All E. wrangeli, indistinguishable from specimens at hand from Wrangell Island." Swarth further reported that, although he found no intergradation between Clethrionomys wrangeli from Flood Glacier and the nearly adjacent Clethrionomys rutilus dawsoni, "the two species, however, resemble each other so closely in form, and in some pelages in color also, that wrangeli would seem to be a coastal offshoot of dawsoni...."