_Alberta_: a.s.sineau River, 1920 ft., 10 mi. E and 1 mi. N Kinuso, 6.
_Remarks._--These red-backed mice were taken in various habitats: gra.s.sy areas in aspen and poplar forest, heavy spruce forest with no undergrowth excepting lichens and moss, thick underbrush in river flood plain, and at the site of an old sawmill. The northwestern distribution of this species along the Alaska Highway as found by Alcorn is approximately the same as that found by Rand (1944:44).
Ondatra zibethicus spatulatus (Osgood)
Muskrat
_Fiber spatulatus_ Osgood, N. Amer. Fauna, 19:36, October 6, 1900.
(Type from Lake Marsh, Yukon, Canada.)
_Ondatra zibethica spatulata_ Miller, N. Amer. Land Mamm. 1911, p. 231, December 31, 1912.
_Specimens examined._--Total 2, as follows: _Alaska_: N side Salcha River, 600 ft., 25 mi. S and 20 mi. E Fairbanks, 1; E side Deadman Lake, 1800 ft., 15 mi. NE Northway, 1.
_Remarks._--One muskrat was shot in an old beaver pond on the north side of the Salcha River. A skull from a carca.s.s, that had been left by a trapper the previous winter, was obtained at Deadman Lake.
Phenacomys intermedius mackenzii Preble
Lemming Mouse
_Phenacomys mackenzii_ Preble, Proc. Biol. Soc. Washington, 15:182, August 6, 1902. (Type from Fort Smith, Slave River, Mackenzie, Canada.)
_Phenacomys intermedius mackenzii_ Crowe, Bull. Amer. Mus. Nat.
Hist, 80:403, February 4, 1943.
_Specimen examined._--One from _Yukon Territory_: SE end Dezadeash Lake.
_Remarks._--A subadult taken only a few miles from the Alaskan border in Yukon Territory const.i.tutes an extension of the known range of this species to the northwest. The mouse is evidently rare or irregular in its distribution since Alcorn did considerable trapping in the area from which only one was taken.
Microtus pennsylvanicus
Pennsylvania Meadow Mouse
The Pennsylvania meadow mouse is an abundant mammal along the Alaska Highway. Alcorn obtained specimens at most of his trapping stations, frequently in company with _Microtus oeconomus_ at the more northern localities. A preferred habitat was gra.s.sy areas and willow clumps along streams or at the edges of lakes. The best catches were made along well-used runways, especially where there were piles of cut gra.s.s. These runways were used also by _Clethrionomys_ and other small animals. Specimens of _M. pennsylvanicus_ were frequently taken in the daytime; one was taken on June 29 as it was swimming at the edge of a small lake near the junction of the Liard River and Irons Creek in British Columbia.
Lacking sufficient comparative material in the past, most workers have considered that _M. pennsylvanicus_ ranges without appreciable geographic variation throughout most of northwestern Canada and Alaska, where it has been referred to the subspecies, _M. p.
drummondii_. Dale (1940), in studying collections made in British Columbia and southeastern Alaska, found evidence of geographic variation and recognized two new subspecies; thus he not only pointed out geographically variable characters but reduced the size of the range ascribed to _M. p. drummondii_. A later work by Rand (1943) considered the northwestern populations of _M. pennsylvanicus_ as being too variable to show distinctive groupings. The large collection made by Alcorn offers evidence that other separable subspecies with constant characters are present. Study of this material indicates the presence of two unnamed subspecies, which are named and described as follows:
Microtus pennsylvanicus alcorni new subspecies
_Type._--Female, adult, skin with skull, No. 21552, Univ. Kansas, Mus.
Nat. Hist., 6 mi. SW Kluane, 2550 feet elevation, Yukon Territory, Canada; 24 August 1947; obtained by J. R. Alcorn; original No. 5240.
_Range._--Extreme southwestern Yukon Territory and adjacent parts of Alaska as far south as Haines, as far north as Northway, and as far west along the Alaskan coast as Anchorage and Tyonek.
_Diagnosis._--Size large (see measurements); color of upper parts near (_l_) Brussels Brown; skull noticeably ridged; zygomatic arches heavy, rounded and relatively short; rostrum heavy; auditory bullae not greatly expanded; maxillary teeth relatively heavy and low-crowned.
_Comparisons._--From _M. p. drummondii_ (specimens from vicinity of Whitehorse, Y. T., Trutch, B. C., and Kinuso, Alberta), _M. p.
alcorni_ differs as follows: Averaging larger in all measurements taken except lengths of tail and hind foot, which are the same; color of upper parts slightly paler and more gray and less brown; underparts paler; zygomatic arches heavier, rounder and shorter; skull proportionately more ma.s.sive, except the auditory bullae which are less inflated; maxillary teeth heavier and lower-crowned.
From _M. p. rubidus_ (specimens from Atlin, B. C.), _M. p. alcorni_ differs as follows: Averaging larger in all cranial measurements taken except length of the maxillary tooth-row which is the same; color of upperparts more gray and less brown; underparts darker; skull longer with longer nasals and heavier zygomatic arches; skull of adult more heavily ridged.
From _M. p. admiraltiae_ (specimens from Admiralty Island), _M. p.
alcorni_ differs as follows: Averaging larger in all measurements taken; color of upper parts more gray and less brown, underparts darker.
_Remarks._--_Microtus p. alcorni_ is a well-defined subspecies differing markedly from adjacent subspecies by a larger and heavier skull and broader, more rounded and heavier zygomatic arches.
Characters examined in the specimens available are constant. Specimens from Haines are slightly darker than those from Kluane. An adult (No.
21534, UKMNH) from Northway has slightly more inflated auditory bullae than those from Kluane. An adult from Tyonek (No. 986, UKMNH) has richer brown upper parts. Measurements of this specimen resemble closely those of animals from Kluane, although the rostrum is noticably heavier.
Several adults were available from many of the localities of occurrence of _M. p. alcorni_. At the locality 9 miles west and 4 miles north of Haines, there were four which were considered to be old adults. These four had larger measurements than others considered to be fully adult. In addition, the skulls were larger and more rugged.
There were occasionally old adults in other series. For the sake of uniformity, I have not considered these aforementioned old adults in the comparative studies of younger adults. This subspecies is named in honor of J(oseph). R(aymond). Alcorn, the collector.
_Measurements._--Average and extreme measurements of six adults of both s.e.xes of _M. p. alcorni_ from the type locality are as follows: Total length, 162 (149-172); length of tail, 43 (39-45); condylobasal length, 26.3 (25.6-26.3); basal length, 25.2 (24.2-25.9); length of nasals, 7.3 (6.9-7.5); zygomatic breadth, 15.3 (14.9-15.6); breadth across auditory bullae, 12.8 (12.4-13.2); alveolar length of upper molariform tooth-row, 6.4 (6.1-6.7). Seven adults of both s.e.xes from 9 miles west and 4 miles north of Haines have the following measurements: 158 (148-165); 45 (41-50); 26.1 (25.5-26.8); 24.8 (24.4-25.7); 7.3 (7.0-7.6); 14.9 (14.3-15.1); 12.2 (11.8-13.0); 6.2 (5.9-6.3).
_Specimens examined._--Total 65, distributed by localities of capture as follows and deposited in the University of Kansas Museum of Natural History: _Alaska_: E side Deadman Lake, 1800 ft., 15 mi. SE Northway, 7; 1 mi. NE Anchorage, 100 ft., 1; Tyonek, Cook"s Inlet, 1; E side Chilkat River, 100 ft., 9 mi. W and 4 mi. N Haines, 37. _Yukon Territory_: 6 mi. SW Kluane, 2250 ft., 14; SW end Dezadeash Lake, 2; 1 mi. S and 3 mi. E Dalton Post, 2500 ft., 3. Specimens reported by Osgood (1904:35) have not been seen by me but may be of this subspecies, and are tentatively referred to it. These are from the following localities in Alaska: Lake Clark near Keejik, near the mouth of the Chulitna River, and Kakhtul River near the junction with the Malchatna.
Microtus pennsylvanicus tananaensis new subspecies
_Type._--Female, adult, skin with skull, No. 21509, Univ. Kansas, Mus.
Nat. Hist., Yerrick Creek, 21 mi. W and 4 mi. N Tok Junction, Alaska; 20 July 1947; obtained by J. R. Alcorn; original No. 5023.
_Range._--East-central Alaska as far south as Tok Junction, as far west as Mt. McKinley, as far north as Fairbanks and as far east as Eagle.
_Diagnosis._--Size medium (see measurements); color of upper parts dark, near (_n_) Prout"s Brown, with some individual variation; skull with zygomatic arches moderately heavy and wide; nasals relatively long; auditory bullae inflated.
_Comparisons._--From _M. p. alcorni_ (see description), _M. p.
tananaensis_ differs as follows: Smaller in all measurements taken except alveolar length of upper molariform tooth-row which is the same; color of upper parts darker, more richly brown and less gray; underparts darker; zygomatic arches less ma.s.sive and narrower; auditory bullae larger and more inflated.
From _M. p. drummondii_ (see comparisons under _M. p. alcorni_), _M.
p. tananaensis_ differs as follows: Larger in all cranial measurements taken except nasal length which is the same; color everywhere slightly darker; wider across zygomatic arches; zygoma thicker; nasals, relative to length of skull, shorter; auditory bullae larger and more inflated.
_Remarks._--For the most part the material available of this subspecies consisted of subadults; however, comparison of adults with those of adjacent subspecies indicates that this subspecies can be distinguished by color of the upper parts, cranial measurements, and size of the zygomatic arches and the auditory bullae. Specimens from 14 miles east and 25 miles north of Fairbanks are especially dark. One subadult (No. 21467, UKMNH) has blackish hair on the feet and a blackish unicolored tail. No. 241696, USBS, an old adult female, from Ketchumstock, is larger.
The specimens referred to this subspecies, vary some in color, but vary less in cranial characters. Additional adults are needed from western Alaska to determine how far this subspecies extends down the valley of the Yukon River. Bailey (1900:24) lists one specimen from Nulato, as _drummondii_; I have not seen it but on geographic grounds tentatively a.s.sign it to _M. p. tananaensis_.
_Measurements._--Measurements of the type specimen are as follows: Total length, 160; length of tail, 40; condylobasal length, 26.0; basal length, 24.9; length of nasals, 6.7; zygomatic breadth, 14.5; breadth across auditory bullae, 12.5; alveolar length of upper molariform tooth-row, 6.2. Two specimens from Eagle (Nos. 128295 and 128320, USBS) have the following measurements respectively: 161, 154; 37.5, 36; 25.3, 25.4; 23.8, 23.9; 6.5, 6.8; 14.5, 14.6; 11.9, 12.3; 6.1, 6.1.
_Specimens examined._--Total 34, distributed by localities of capture as follows and unless otherwise stated in the University of Kansas Museum of Natural History: _Alaska_: Near Buster Creek, Chatanika River, 1 (USBS); Chatanika River, 700 ft., 14 mi. E and 25 mi. N Fairbanks, 4; Fairbanks, 2 (USBS); head of Glacier Creek, Mt.
McKinley, 1 (USBS); Moose Creek, Mt. McKinley, 2 (USBS); head of Toklat River, 1 (USBS); Eagle, 4 (USBS); Yerrick Creek, 21 mi. W and 4 mi. N Tok Junction, 13; Ketchumstock, 2 (USBS); 9 mi. from mouth of Robertson River, 1 (USBS); Tanana, 3 (USBS); Tanana Crossing, 1 (USBS). Osgood (1909b:24) records specimens which may be of this subspecies from the following localities in Alaska: Charlie Creek, Circle, 20 miles above Circle, 40 miles above Circle, Nation Creek, and Seventy Mile Creek. Osgood (1900:36) also records specimens from near Fort Yukon. None of these has been seen by me; they are only tentatively a.s.signed to this subspecies.
Microtus pennsylvanicus drummondii (Audubon and Bachman)
_Arvicola drummondii_ Audubon and Bachman, Quadr. North Amer., 3:166, 1854. (Type, by subsequent designation, from vicinity of Jasper House, Alberta.)