Part 10

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 massive 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 assign 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 assigned 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.)

Microtus pennsylvanicus drummondii Hollister, Canadian Alp. Jour., Special Number, p. 23, February 17, 1913.

Specimens examined.--Total 93, as follows: Yukon Territory: McIntyre Creek, 2250 ft., 3 mi. NW Whitehorse, 26; W side Lewes River, 2150 ft., 2 mi. S Whitehorse, 4; 5 mi. W Teslin River, 2400 ft., 16 mi. S and 53 mi. E Whitehorse, 7; E side Teslin River, 2300 ft., 16 mi. S and 59 mi. E Whitehorse, 1. British Columbia: 1 mi. NW jct. Irons Creek and Liard River, 8; Hot Springs, 3 mi. WNW jct. Trout River and Liard River, 3; N side Liard River, 1/2 mi. W jct. Liard River and Trout River, 1; 1/4 mi. S jct. Trout River and Liard River, 13; S side Toad River, 10 mi. S and 21 mi. E Muncho Lake, 2; Summit Pass, 4200 ft., 10 mi. S and 70 mi. W Fort Nelson, 2; E side Minaker River, 1 mi. W Trutch, 19; Beatton River, 115 mi. S Fort Nelson, 1; 5 mi. W and 3 mi. N Fort St. John, 2. Alberta: Assineau River, 1920 ft., 10 mi. E and 1 mi. N Kinuso, 4.

Remarks.--Adults among the specimens listed above vary but little; one female from Assineau River in Alberta is notably more reddish than others taken elsewhere.

Average and extreme measurements of nine adults of both sexes of M. p. drummondii from E side Minaker River, 1 mi. W Trutch, British Columbia, are as follows: Total length, 157 (148-165); length of tail, 42 (37-46); condylobasal length, 25.1 (24.7-26.0); basal length, 24.2 (23.4-25.0); length of nasals, 6.8 (6.4-7.2); zygomatic breadth, 14.4 (13.9-14.7); breadth across auditory bullae, 12.4 (12.0-12.7); alveolar length of upper molariform tooth-row, 6.1 (6.0-6.2); Nine adults of both sexes from McIntyre Creek, 2250 ft., 3 miles northwest of Whitehorse, Yukon Territory, have the following measurements: 153 (147-168); 40 (33-47); 24.9 (24.2-25.5); 24.0 (23.6-24.6); 6.6 (6.2-7.2); 14.4 (13.9-15.1); 12.1 (11.7-12.5); 6.1 (6.0-6.2).

Microtus cf. cantator Anderson

Yukon Singing Mouse

Microtus cantator Anderson, Nat. Mus. Canada, Bull. No. 102, Biol. Ser. No. 31:161, [for 1946], January 24, 1947. (Type "taken in tundra-slide above timber-line on mountain top near Tepee Lake on north slope of St. Elias Range," Yukon Territory, Canada.)

Specimen examined.--One from Alaska: Fish Creek, 3400 ft., 5 mi. N and 1 mi. E Paxson.

Remarks.--The single adult male, obtained by Alcorn, has been compared by Dr. Henry W. Setzer with specimens of Microtus muriei Nelson, M. miurus miurus Osgood, and M. m. oreas Osgood in the United States National Museum. He reports that the specimen is related most closely to M. miurus but exhibits characters by which it is, at least, subspecifically distinct from these two forms of this species. Three specimens of M. andersoni Rand and one of M. cantator Anderson, borrowed from the National Museum of Canada are less mature than the specimen in question. Even so, the male from Fish Creek is less gray than M. andersoni and as seen from measurements of the type, an adult male (Rand, 1945:42), is larger with longer tail and has a shorter and narrower skull and is judged to be taxonomically separable. M. cantator was named from two specimens; both the paratype (seen by me) and seemingly the type are too young to show clearly subspecific characters. Alcorn's specimen is tentatively referred to M. cantator until some adult topotypes can be obtained. Measurements of the male, No. 21539, from Fish Creek, are: Total length, 152; length of tail, 30; hind foot, 22; condylobasal length, 28.0; basal length, 26.6; length of nasals, 7.1; zygomatic breadth, 13.8; breadth across auditory bullae, 11.5; least interorbital breadth, 3.3; alveolar length of upper molariform tooth-row, 6.2.

Alcorn took this specimen in an area above timberline where a low growth of willow was the dominant vegetation. Traps were set where he had seen a mouse go into a small burrow. The next morning, August 18, 1947, he found this specimen and two Microtus oeconomus macfarlani in his traps.

Microtines of the subgenus Stenocranius from continental areas of Alaska and Northwestern Canada are represented in collections by a few specimens from widely separated localities. Lacking material from intermediate localities, describers have given specific recognition to several of these isolated populations. Future collecting will be necessary to disclose whether the North American mice of this subgenus belong to one or to more than one species and may disclose whether or not there has been more than one invasion of the North American continent by members of this Asiatic group.

Microtus longicaudus vellerosus J. A. Allen

Long-tailed Meadow Mouse

Microtus vellerosus J. A. Allen, Bull. Amer. Mus. Nat. Hist., 12:7, March 4, 1899. (Type from upper Liard River, British Columbia, Canada.)

Microtus longicaudus vellerosus Anderson and Rand, Canadian Field-Nat., 58:20, April 1, 1944.

Specimens examined.--Total 127, as follows: Alaska: N side Salcha River, 600 ft., 25 mi. S and 20 mi. E Fairbanks, 1. Yukon Territory: 6 mi. SW Kluane, 2550 ft., 2; McIntyre Creek, 2250 ft., 3 mi. NW Whitehorse, 10; 1/2 mi. W Whitehorse, 1; SW end Dezadeash Lake, 18; 11/2 mi. S and 3 mi. E Dalton Post, 2500 ft., 24. British Columbia: Stonehouse Creek, 51/2 mi. W jct. Stonehouse Creek and Kelsall River, 20; Hot Springs, 3 mi. WNW jct. Trout River and Liard River, 4; 1/4 mi. S jct. Trout River and Liard River, 15; S side Toad River, 10 mi. S and 21 mi. E Muncho Lake, 27; SE end Muncho Lake, 4; Summit Pass, 4500 ft., 10 mi. S and 70 mi. W Fort Nelson, 1.

Remarks.--Specimens from 11/2 miles south and 3 miles east of Dalton Post and from Dezadeash Lake in Yukon Territory and from Stonehouse Creek in British Columbia are referred to M. l. vellerosus although in color of upper parts they show close relationship with M. l. littoralis. These specimens are less gray and more brown than specimens more typical of M. l. vellerosus from the Liard River area.

Alcorn found the long-tailed meadow mouse in widely separated areas. Most specimens were obtained in grassy situations near water or on moist ground. The single male from Summit Pass in British Columbia was taken above timberline.

Microtus longicaudus littoralis Swarth