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Zapus pacificus

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Southern Pacific Jumping Mouse
(Zapus pacificus)
Range
Taxonomic classification
Order:Rodentia
Suborder:Supramyomorpha
Infraorder:Myomorphi
Superfamily:Dipodoidea
Family:Zapodidae
Genus:Zapus
Binomial details
Zapus pacificus Merriam, 1897

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 Zapus princeps pacificus to species status. 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

From Merriam (1897) for the type specimen of Zapus pacificus from Prospect, Rogue River Valley, Oregon: "Size rather small; dorsal area strongly suffused with yellowish. Dorsal area not strongly defined, but so strongly saturated with yellow that the yellow predominates over the black; sides buffy yellow, moderately lined with black hairs; inner side of legs only slightly darkened; tail sharply bicolor: grayish above, white beneath; fore and hind feet soiled white."

From Krutzsch (1954), describing Zapus princeps pacificus: "Size medium; color bright; back near Ochraceous-Buff with admixture of black hair forming dark dorsal band; sides bright Ochraceous-Buff with fine admixture of black hair; lateral line blending with color of sides or wanting or indistinct; ventral surface white; tail bicolored, grayish-brown above, yellowish-white below, in some specimens with white tip; feet grayish-white above; ears dark, edged with Ochraceous Buff; braincase relatively narrow; incisive foramina relatively short; pterygoid fossae usually broad; proximal part of inferior ramus of zygomatic process of maxillary broad; postpalatal notch usually broadly rounded; auditory bullae relatively small and flattened; nasals parallel sided; maxillary tooth-row short; interorbital region moderately broad."

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
California (Yosemite National Park) Hall (1946) 207–232 (n=12) 115–138 (n=12) 30–33 (n=12) 17.8–27.5 (n=12)
Oregon (Jackson and Josephine Counties) Verts & Carraway (1998) males: 218–222 (n=3) males: 131–141 (n=3) males: 31–32 (n=3)
Oregon (Prospect, Rogue River Vallet, Z. princeps pacificus type) Merriam (1897) 225 141 31
Oregon (Strawberry Butte) Preble (1899) 243 (n=3) 146 (n=3) 32 (n=3)


Skull

From Merriam (1897) for the type specimen of Zapus pacificus from Prospect, Rogue River Valley, Oregon: "Contrasted with Zapus montanus the skull of Z. pacificus is smaller; the rostrum and nasals shorter; audital bullae smaller; basioccipital broader between bullae; interpterygoid fossa shorter; upper molar series more divaricating anteriorly."

Jones (1981) noted that the 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 Malaney et al.'s (2017) species delimitations.

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Similar species

Where the range of Zapus pacificus meets that of the Oregon Jumping Mouse (Zapus oregonus), differentiating these two species using morphological characters may be difficult. Krutzsch (1954) found that Z. p. pacificus differed from Z. p. oregonus in "being brighter in all pigmented areas; more ochraceous and less yellow laterally; dorsally more ochraceous and less black; size averaging smaller; maxillary tooth-rows shorter; auditory bullae less inflated and smaller; interorbital region averaging narrower; palatal bridge averaging shorter; incisive foramina shorter and posteriorly narrower; nasals parallel rather than narrowed posteriorly."

  • Range of Zapus pacificus proposed by Malaney et al. (2017).
  • Range of Zapus oregonus proposed by Malaney et al. (2017).

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 Zapus princeps pacificus to species status. 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.

  • Zapus princeps subspecies boundaries as defined by Krutzsch (1954).
  • Distribution of Zapus pacificus based on genetic analyses and niche-based geographic distribution modeling by Malaney et al. (2017).

References

Hall ER. 1946. Mammals of Nevada. Berkeley and Los Angeles (CA, USA): University of California Press.

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.

Merriam CH. 1897-04-26. Three new jumping mice (Zapus) from the northwest. Proceedings of the Biological Society of Washington 11:103-104.

Naughton D. 2012. The natural history of Canadian mammals. Toronto (ON, CA): University of Toronto Press.

Preble EA. 1899-08-08. Revision of the jumping mice of the genus Zapus. North American Fauna 15:1-44.

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