Zapus saltator
| Northwestern Jumping Mouse
(Zapus saltator) | |
|---|---|
| Range | |
 | |
| Taxonomic classification | |
| Order: | Rodentia |
| Suborder: | Supramyomorpha |
| Infraorder: | Myomorphi |
| Superfamily: | Dipodoidea |
| Family: | Zapodidae |
| Genus: | Zapus |
| Binomial details | |
| Zapus saltator J. A. Allen, 1899 | |
| Other resources | |
| Full taxonomic details at MDD | |
Recently, molecular studies have found that the taxonomy and species delineations within Zapus are complex (Malaney et al., 2013). Malaney et al. (2017) recognized 9 species within Zapus, elevating some of the subspecies in Krutzsch's (1954) revision of jumping mice to species status. Genetic approaches by Malaney et al. (2017) supported elevating this taxon to species status. The delineation of this taxon by Malaney et al. (2017) includes the following subspecies: Zapus princeps idahoensis, Zapus princeps kootenayensis, Zapus princeps minor, Zapus princeps saltator, and part of Zapus princeps utahensis. The work of Malaney et al. (2017) has importantly exposed cryptic diversity and putative new species within Zapus. Further studies will be needed to fully understand new species boundaries and morphological variation.
Description
A formal species description for Zapus saltator currently does not exist. The following descriptions from Krutzsch (1954) are provided for subspecies that Malaney et al. (2017) subsumed under Zapus saltator.
From Krutzsch (1954), describing then Zapus princeps idahoensis from Banff, Alberta, southward through extreme southwestern Alberta and extreme southwestern British Columbia, most of the panhandle of Idaho, Kamiak Butte in eastern Washington, western Montana, and western Wyoming (Green, Wind River and Absoroka ranges of the Rocky Mt’s), which is now included in Zapus saltator: "Size, medium; back from near Clay Color to near Warm Buff, usually overlaid with black hairs forming broad dorsal band; sides lighter than back; lateral line indistinct or wanting; belly pure white, occasionally faintly tinged with Ochraceous-Buff; tail indistinctly bicolored, tan to grayish-white below and pale brown above; hind feet grayish-white above; ears dark, edged with white or yellowish-white; postpalatal notch anterior to posterior border of last molars; proximal part of inferior ramus of zygomatic process of maxillary relatively narrow and usually without enlarged median projection; auditory bullae well inflated; incisive foramina relatively narrow."
From Krutzsch (1954), describing then Zapus princeps kootenayensis from Glacier in the Selkirk Range, British Columbia, south to 5 mi. W Cocolalla, Bonner County, Idaho, west and north to Sullivan Lake, Pend Oreille County, Washington; and northwestward to Manning Park on the eastern summit of the Cascade Range in British Columbia, which is now included in Zapus saltator: "Size, medium; color moderately dark; upper parts noticeably dull and dusty; broad dorsal band of dull Ochraceous-Buff to near Warm Buff sprinkled with black hair to a varying degree, resulting in two color phases (dark has more black hair; Ochraceous phase or Warm Buff phase has more brown hair); sides paler than back owing to fewer black hairs; lateral line, when present, narrow and dull; ventral surface pure white; tail bicolored, pale brown above, yellowish-white to dull white below; ears dark with narrow white or yellowish-white edgings; feet white above; skull narrow across zygomata; incisive foramina narrow; bullae moderately inflated; nasals narrow at tips; postpalatal notch anterior to posterior face of last molars; braincase moderately narrow; zygomatic arch short."
From Krutzsch (1954), describing then Zapus princeps minor from most of southern half of Saskatchewan and Alberta, northeastern Montana southeastward to Aweme, Manitoba, and Webster, South Dakota, which is now included in Zapus saltator: "Size, small; back dark, usually with a distinct mid-dorsal band of black mixed with Warm Buff; sides lighter, more yellowish, but always with an admixture of black hairs; lateral line distinct, near Ochraceous-Buff, ventral surface characteristically suffused with Ochraceous-Buff; tail bicolored, grayish-white to yellowish-white below and pale brown above; hind feet grayish-white above; ears dark, edged with white or yellowish-white; skull small; postpalatal notch often anterior to posterior part of molars; inferior ramus of zygomatic process of maxillary often with well developed medial projection; auditory bullae flattened; nasals narrower anteriorly and proximal third depressed; base of zygomatic process of squamosal broad."
From Krutzsch (1954), describing then Zapus princeps saltator from Southern Yukon and southeastern Alaska south in British Columbia, to Bella Coola Inlet and Glacier, which is now included in Zapus saltator: "Size medium; back near Ochraceous-Buff, overlaid with black hairs forming dark dorsal band thickly flecked with ochraceous; sides lighter than back; lateral line usually distinct; belly pure white, sometimes faintly suffused with Ochraceous-Buff; tail bicolored, dark above and grayish-white below; hind feet grayish-white above; ears dark, edged with yellowish-white or Ochraceous-Buff; incisive foramina long, broad posteriorly; palatal bridge relatively short; postpalatal notch anterior to posterior border of last molars; proximal part of inferior ramus of zygomatic process of maxillary without enlarged median projection; zygomatic arch short."
From Krutzsch (1954), describing then Zapus princeps utahensis from Southeastern Idaho and extreme western Wyoming (Teton, Snake, and Uinta Mt’s) southward through Uinta, Wasatch, Oquirrh, and Beaver Mt’s of Utah, which is now partly included in Zapus saltator: "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."
External measurements
Length measurements are in millimeters (mm) and weight measurements are in grams (g), unless stated otherwise. If available, the sample size (n=) is provided. If a range is not provided and n= is not given, then the listed measurement represents an average.
| Part of range | Reference | Total length | Tail length | Hindfoot length | Ear length | Mass |
|---|---|---|---|---|---|---|
| North Dakota | Seabloom et al. (2020) | 215 | 126 | 28 | 12 | 20 |
| Saskatchewan (Wingard, near Carlton House, Z. princeps minor type locality) | Preble (1899) | 220 (n=2) | 131.5 (n=2) | 28 (n=2) |
Skull
From Jones (1981): "paracone in the M1 and M2 is attached to the body of the tooth." See the Taxonomic notes section under Zapus for how the M1 and M2 characters noted by Jones (1981) were evaluated and applied to this taxon.
Similar species
Where Zapus saltator is sympatric with the Northern Meadow Jumping Mouse (Zapus hudsonius) and the Northern Pacific Jumping Mouse (Zapus trinotatus), it may be possible to differentiate these species based on size (but this can be difficult in the field), color of the ear fringe, and shape of M1 and M2. Where the ranges of Zapus saltator and the Oregon Jumping Mouse (Zapus oregonus) meet, differentiating these two species may not currently be possible using morphological characters. A formal taxonomic revision of these two species is needed and may identify suitable characters for differentiating this pair.
Zapus saltator 
Zapus hudsonius 
Zapus trinotatus
Area of sympatry for Z. hudsonius and Z. saltator 
Area of sympatry for Z. trinotatus and Z. saltator
After reviewing Krutzsch (1954) and Malaney et al. (2017), it appears that the color of the ear fringe is useful for distinguishing Z. hudsonius and Z. trinotatus from Z. saltator (at least in the USA). The ears of Z. hudsonius and Z. trinotatus are dark and narrowly edged with color of sides or edged with ochraceous, while the ears of Z. saltator are dark and edged with white or yellowish-white. Under Malaney et al.'s (2017) proposed species boundaries, it appears that the ear fringe character is useful for distinguishing Z. saltator from Z. hudsonius and Z. trinotatus. See the Taxonomic notes section under Zapus for how the ear fringe character noted by Krutzsch (1954) was evaluated and applied to Malaney et al.'s (2017) species delimitations.
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Zapus saltator ears are dark and edged with white or yellowish-white. -
In much of their range, Zapus hudsonius lack white fringes on the ears. -
Zapus trinotatus lack white fringes on the ears.
Jones (1981) noted that the shape and attachment of the paracone to the M1 and M2 (upper molars) was helpful for differentiating species of Zapus. Using Malaney et al. (2017) delimitations, we find that for Z. trinotatus and Z. hudsonius the paracone in the M1 and M2 is isolated, while the paracone in the M1 and M2 is attached to the body of the tooth in Z. saltator. This character may not hold up in the Alaska Peninsula, coastal section of mainland of southern and southeastern Alaska including Revillagigedo Island and southwestern Yukon range of Z. hudsonius, where Jones (1981) noted that paracone in the M2 is isolated, but the paracone of M1 may or may not be isolated. See the Taxonomic notes section under Zapus for how the M1 and M2 characters noted by Jones (1981) were evaluated and applied to Malaney et al.'s (2017) species delimitations.
Taxonomic notes
Recently, molecular studies have found that the taxonomy and species delineations within Zapus are complex (Malaney et al., 2013). Malaney et al. (2017) recognized 9 species within Zapus, elevating some of the subspecies in Krutzsch's (1954) revision of jumping mice to species status. Genetic approaches by Malaney et al. (2017) supported elevating this taxon to species status. The delineation of this taxon by Malaney et al. (2017) includes the following subspecies: Zapus princeps idahoensis, Zapus princeps kootenayensis, Zapus princeps minor, Zapus princeps saltator, and part of Zapus princeps utahensis. The work of Malaney et al. (2017) has importantly exposed cryptic diversity and putative new species within Zapus. Further studies will be needed to fully understand new species boundaries and morphological variation.
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Zapus princeps subspecies boundaries as defined by Krutzsch (1954). -
Distribution of Zapus saltator based on genetic analyses and niche-based geographic distribution modeling by Malaney et al. (2017).
References
Allen JA. 1899. On mammals from the Northwest Territory collected by Mr. A.J. Stone. Bulletin of the American Museum of Natural History 12(1):1-9.
Jones GS. 1981. The systematics and biology of the genus Zapus (Mammalia, Rodentia, Zapodidae)(Canada, United States) (Doctoral dissertation, Indiana State University).
Krutzsch PH. 1954. North American jumping mice (genus Zapus). University of Kansas Publications, Museum of Natural History 7:349-472. Link.
Malaney JL, Demboski JR, Cook JA. 2017. Integrative species delimitation of the widespread North American jumping mice (Zapodinae). Molecular Phylogenetics and Evolution 114: 137-152.
Seabloom R, Hoganson JW, Jensen WF. 2020. The mammals of North Dakota. Fargo (ND, USA): North Dakota State University Press.