Description.—Size medium; color dull, back from near Clay Color to near Tawny-Olive with admixture of black hair forming poorly defined dorsal band; sides lighter than back from near Clay Color to near Cinnamon-Buff; lateral line distinct and clear Ochraceous-Buff; belly white, sometimes with faint wash of clear Ochraceous-Buff; tail bicolored, brownish to light brownish-black above, grayish-white to yellowish-white below; ears dark, narrowly edged with color of sides; feet grayish-white above; incisive foramina relatively narrow and elongate; auditory bullae moderately inflated; pterygoid fossae relatively broad; postpalatal notch broadly rounded; interorbital region relatively narrow; zygomatic arch not widely bowed; frontal region well inflated; distance from incisors to postpalatal notch relatively short.
Comparisons.—Among named subspecies, Zapus hudsonius preblei most closely resembles Z. h. campestris. From topotypes of Z. h. campestris, Z. h. preblei differs as follows: Upper parts generally dull, averaging lighter, less black-tipped hair; dorsal band less distinct; sides duller; averaging smaller in most cranial measurements taken; least interorbital constriction narrower; auditory bullae smaller, less well inflated; incisive foramina narrower, not truncate posteriorly; frontal region usually more inflated.
From Zapus hudsonius pallidus, Z. h. preblei differs as follows: Upper parts generally duller (less ochraceous); dorsal band less distinct; sides paler (not bright Ochraceous-Buff); zygomatic arch less widely bowed; least interorbital constriction narrower; occipitonasal length averaging greater; distance from [453] incisors to postpalatal notch averaging less; incisive foramina longer, proportionally less widely bowed; auditory bullae longer; pterygoid fossae averaging broader.
Remarks.—No evidence of intergradation with any other geographic race was noted. To the east the range of Z. h. preblei is separated from that of Z. h. pallidus (western Kansas and southwestern Nebraska), by several hundred miles of mixed and short grass prairie. Much of this area is unsuitable to jumping mice but local marshy places might be inhabited. Much territory inhospitable to Zapus intervenes also between the ranges of Z. h. preblei and Z. h. campestris. This area (northern Platte, Goshen, eastern Converse, Niobrara, and southern Weston counties, Wyoming) is chiefly rolling hills and short grass prairie and, like that to the east, is only locally suitable for Zapus. If jumping mice do occur in suitable places in these intervening areas it is to be expected that they will show intergradation between the subspecies concerned.
Zapus hudsonius preblei, on the basis of 11 specimens, agrees most closely in size and color with Z. h. campestris; there is much less resemblance between Z. h. preblei and Z. h. pallidus.
An adult from Springhill, 12 mi. N Laramie Peak, is typically Z. h. preblei as is one from Cheyenne.
Although specimens of Z. h. preblei are few (4 adult, 7 non-adults), the differences between this and neighboring named kinds is considerable.
Specimens examined: Total, 11, distributed as follows:
Colorado: Boulder County: 3 mi. E Boulder, 1 (UCM); 5 mi. E Boulder, 1 (UCM); south of Boulder (no exact locality), 1 (UCM). Jefferson County: Semper, 1. Larimer County: Loveland, 2 (USBS).
Wyoming: Albany County: Springhill, 12 mi. N Laramie Peak, 6300 ft., 3 (USBS). Laramie County: Cheyenne, 1 (USNM). Platte County: Chugwater, 1 (Clev. MNH).