Zapus hudsonius alascensis, Osgood, N. Amer. Fauna, 19:38, October 6, 1900.
Type.—Type specimen not known to be in existence; from Hudson Bay, locality now considered to be Fort Severn, Ontario (see Anderson, 1942:37).
Range.—Central Alaska southeastward to central Ontario, northern Minnesota, northern Wisconsin, and upper peninsula of Michigan. See [fig. 47]. Zonal range: Hudsonian, Canadian, and into Transition.
Description.—Size medium; back dark, from near Tawny-Olive to near Cinnamon with heavy admixture of black hair forming dorsal band; sides lighter than back and from near Tawny-Olive to near Cinnamon, sometimes with admixture of black hair giving sides streaked appearance; lateral line usually distinct, clear Ochraceous-Buff; underparts white, sometimes with slight suffusion of Ochraceous-Buff; tail bicolored, brown to brownish-black above, grayish-white to yellowish-white below; ears dark, usually edged with ochraceous; feet grayish-white above; incisive foramina relatively short and broadly rounded; zygomata relatively short; braincase relatively broad; auditory bullae flat, long, and relatively broad; pterygoid fossae relatively narrow; nasals relatively broad and short.
Comparisons.—From Zapus hudsonius alascensis, Z. h. hudsonius differs as follows: upper parts generally darker, more black tipped hair; sides darker with greater suffusion of dark hair; lateral line brighter, more distinct; size averaging smaller; zygomatic arches less bowed outward; distance from incisors to postpalatal notch shorter; zygomata shorter; occipitonasal length less; mastoid region narrower.
From Zapus hudsonius intermedius, Z. h. hudsonius differs in: color darker, more tawny dorsally; sides averaging darker, more black-tipped hairs; size averaging larger; braincase averaging broader; distance from incisors to postpalatal notch averaging slightly shorter; zygomata averaging longer; mastoid region averaging broader; incisive foramina averaging shorter.
From Zapus hudsonius tenellus, Z. h. hudsonius differs as follows: upper parts averaging darker; tail averaging shorter; condylobasal length averaging more; braincase averaging broader; auditory bullae broader and less inflated; interparietal averaging broader; incisive foramina more broadly rounded and averaging longer.
For comparison with Zapus hudsonius canadensis and Zapus hudsonius campestris see accounts of those subspecies.
Remarks.—Preble (1899:16) had available for study five specimens of Zapus hudsonius hudsonius from Hudson Bay. Four were preserved in alcohol and one as an incomplete skin (prepared from an alcoholic specimen). All were unreliable for comparative purposes owing to the effects of the preservative. Preble, therefore, (loc. cit.) selected as a fairly typical sample a series of specimens from Tower, St. Louis County, Minnesota; these formed the basis of comparison between Z. h. hudsonius and other subspecies of Zapus hudsonius. Now that additional material (well prepared skins and skulls) is available from the Hudson Bay region and from other localities in northern and western Canada it is evident that the specimens from Tower, although here considered to be Z. h. hudsonius, are not typical Z. h. hudsonius but are intergrades between hudsonius and specimens of Zapus hudsonius intermedius. Comparisons made in the present account are based on specimens from the vicinity of Hudson Bay (Fort Severen, Ontario, York Factory, Shamatawa River, and Robinson Portage, Manitoba). These individuals are considered typical of this subspecies. With these new data available the range of Z. h. hudsonius is now understood to include all of the region from eastern Alaska to the northern parts of Minnesota, Wisconsin, and Michigan.
Intergradation between Zapus hudsonius canadensis and Z. h. hudsonius is noted in specimens from 30 mi. NE Port Arthur and also in those from Silver Islet, Thunder Cape, Ontario. These individuals resemble Z. h. canadensis in size and shape of the auditory bullae and in the shape of the nasals, but in their darker coloration, broadly rounded incisive foramina, and relatively narrow pterygoid fossae they are more nearly like Z. h. hudsonius to which they are here referred.