North American Jumping Mice (Genus Zapus)

by Philip H. Krutzsch

Range.—Southeastern Idaho and extreme western Wyoming (Teton, Snake, and Uinta Mt’s) southward through Uinta, Wasatch, Oquirrh, and Beaver Mt’s of Utah. See [fig. 46]. Zonal range: Transition, Canadian, and Hudsonian.

Description.—Size, large; back from Cinnamon-Buff to Warm Buff overlaid with black hairs; sides lighter with less admixture of black hairs; lateral line indistinct, sometimes wanting; tail bicolored, brownish-black above, white to yellowish-white beneath; feet grayish-white above; ventral surface white to base of hairs; ears dark, edged with white to yellowish-white; skull large; palatal bridge relatively short; upper tooth-rows diverging anteriorly; occipitonasal length great; interorbital region broad; zygomata widely bowed; postpalatal notch anterior to posterior face of last molars; mastoid width great.

Comparisons.—From Zapus princeps princeps, Z. p. utahensis differs in: color dorsally and laterally less ochraceous, lacking broad lateral line; skull larger in every part measured, excepting length of palatal bridge and breadth of palate at M3; zygomata more bowed; upper tooth-rows more divergent anteriorly; postpalatal notch anterior to posterior border of last molars.

Compared with Zapus princeps cinereus, Z. p. utahensis differs as follows: Size averaging larger; upper parts darker, Cinnamon-Buff not Pinkish-Buff; incisive foramina wider posteriorly; palate wider; zygomata more robust.

For comparison with Zapus princeps idahoensis see account of that subspecies.

Remarks.—Zapus princeps utahensis most closely resembles the several subspecies in the Great Basin in its large size, widely bowed zygomata, and posteriorly broadened incisive foramina. Intergradation between Z. p. utahensis and Zapus princeps cinereus, geographically the nearest of the Great Basin subspecies, is not known. Intergradation in color and cranial characters occurs between Zapus princeps idahoensis and Z. p. utahensis in specimens from 17 mi. E and 4 mi. N of Ashton, Idaho. All these specimens are, however, referable to Z. p. idahoensis. Animals from 9 mi. SE Irwin and from 3 mi. SW Victor, Idaho, resemble Z. p. utahensis in most differential characters (dorsally ochraceous, lateral line more distinct, incisive foramina large, palate broad anteriorly, auditory bullae less inflated), and are here referred to Z. p. utahensis. A series of specimens from the head of Crow Creek, Idaho, were considered by Davis (1939:340) to be intergrades between Z. p. idahoensis and Z. p. utahensis; he thought that the specimens were more nearly like Z. p. utahensis in color, but cranially (80 per cent in average ratio of anterior width of palate to posterior width of palate), more nearly like Z. p. idahoensis, to which subspecies he referred them. I have examined these specimens and find them to be more nearly like Z. p. utahensis not only in color but in cranial characters as well. For example, the average ratio obtained by me for anterior width of palate to posterior width of palate is 72 per cent, rather than 80 per cent as given by Davis (loc. cit.). Other cranial characters, size of the incisive foramina, shape of the foramen magnum, and shape of the auditory bullae, indicate relationship with Z. p. utahensis to which they are here referred. Two immature individuals from Strawberry Creek, 20 mi. E Preston, Idaho, considered to be Z. p. idahoensis by Davis (op. cit.:341), also are here referred to Z. p. utahensis.

Specimens examined.—Total, 178, distributed as follows:

Idaho: Bonnerville County: 9 mi. SE Irwin, 6400 ft., 3. Caribou Co.: Head Crow Creek, Preuss Mts., 7500 ft., 6 (USBS). Franklin County: Strawberry Creek, 20 mi. NE Preston, 6700 ft., 2 (MVZ). Teton County: 3 mi. SE Victor, 6 (MVZ).

Utah: Beaver County: Puffer Lake, 1 (UU). Daggett County: junction Deep Creek and Carter Creek, 7900 ft., 2 (UU). Duchesne Co.: Currant Creek, Uinta Forest, 2 (USBS). Morgan Co.: exact locality not given, 1 (UU). Rich County: 12 mi. SW Woodruff, 1 (MVZ). Salt Lake County: Lambs Canyon, 2 mi. above Parleys Canyon, 7000 ft., 1 (UU); head Lambs Canyon, 9000 ft., 3 (UU); Salamander Lake and Lambs Canyon, 9000 ft., 11 (UU); “The Firs,” Mill Creek Canyon, 2 (UU); Brighton, Silver Lake P. O., 8700 ft., Cottonwood Canyon, 1 (UU); Brighton, Big Cottonwood Canyon, 8000 ft., 1 (UU); 1 mi. above Alta, 4 (UU); Butterfield Canyon, approximately 5 mi. above Butterfield Tunnel, 3 (UU). Sanpete Co.: 8 mi. E Fairview and 5 mi. S Mammoth R. S., Manti Nat’l Forest, 9000 ft., 1 (USBS); Baldy R. S., Manti Nat’l Forest, 1 (UU); Ephraim, 8850 ft., 1 (USBS). Summit County: Henrys Fork, Uinta Mts., 8000 ft., 4 (UU); 14 mi. S and 2 mi. E Robertson, 9300 ft., 3. Uintah County: 21 mi. W and 15 mi. N Vernal, 10,050 ft., 1. Utah County: Payson Lake, 8300 ft., 12 mi. SE Payson, Mt. Nebo, 12 (UU); 1 mi. E Payson Lake, 8300 ft., Mt. Nebo, 3 (UU). Wasatch County: Provo River, 3 mi. N Soapstone R. S., Wasatch Nat’l Forest, 1 (UU).

Wyoming: Lincoln County: 3 mi. N and 11 mi. E Alpine, 5650 ft., 37. Teton County: ¹/₄ mi. E Moran, 6700 ft., 4; Bar B. G. Ranch, 6500 ft., 2¹/₂ mi. NE Moose, 11; [420] Moose, 6225 ft., 1. Uinta County: 2 mi. E Robertson, 7200 ft., 1; 9 mi. S Robertson, 8000 ft., 21; 9 mi. S and 2¹/₂ mi. E Robertson, 8000 ft., 1; 9¹/₂ mi. S and 1 mi. W Robertson, 8600 ft., 2; 10 mi. S and 1 mi. W Robertson, 8700 ft., 18; 10¹/₂ mi. S and 2 mi. E Robertson, 8900 ft., 1; 13 mi. S and 1 mi. E Robertson, 9000 ft., 4; 5 mi. E Lonetree, 1 (ROM).