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Peromyscus eremicus

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Cactus Deermouse
(Peromyscus eremicus)
Range
Taxonomic classification
Order:Rodentia
Suborder:Supramyomorpha
Infraorder:Myomorphi
Superfamily:Muroidea
Family:Cricetidae
Subfamily:Neotominae
Tribe:Peromyscini
Genus:Peromyscus
Binomial details
Peromyscus eremicus (S. F. Baird, 1858)

Peromyscus eremicus was separated into two species by Riddle et al. (2000), assigning Peromyscus fraterculus to populations west of the Colorado River and Peromyscus eremicus to populations east side of the river.

Description

From Veal & Caire (1979): "Externally Peromyscus eremicus is characterized by naked soles on the hind feet; a finely annulated, nearly naked tail which is equal to or usually longer than the head and body; relatively large, sparsely haired and membranous ears; and long, soft, silky pelage. The coloration of the pelage varies among the subspecies and even among different populations. Dark populations are known to occur in the lava areas of Arizona (Benson, 1933), New Mexico (Findley et al., 1975; Koschmann, 1974), and Sonora (Caire, 1978). In general, P. eremicus can be described as having upper parts of ochraceous-buff to cinnamon-buff washed with dusk; a lateral line of pure ochraceous-buff extending from along the sides to the outer surface of the front legs; a slightly bicolored tail, dusky on top and whitish below: sides and a buffy pectoral spot sometimes present. Dice (1939) found the pelage color of female cactus mice to be slightly paler than that of males, and noted that juvenile pelage was usually duller (grayer) and less buffy than the adult pelage."

From Hoffmeister (1986) for Arizona: "A small to medium-sized species of Peromyscus, tail longer than body (in about 90 percent of our specimens, but perhaps in all if measurements more accurately taken), tail sparsely haired so as to appear almost naked, except for more hairs near the tip, tail only slightly bicolor, with the dark color on dorsum grading into color of venter, ears small and not rimmed with white."


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 Jameson & Peeters (2004) 160–200 84–120 18–22 13–20 18–30
Texas Schmidly & Bradley (2016) 185 102 20 20 18–40


Color variation

From Veal & Caire (1979): "The coloration of the pelage varies among the subspecies and even among different populations. Dark populations are known to occur in the lava areas of Arizona (Benson, 1933), New Mexico (Findley et al., 1975; Koschmann, 1974), and Sonora (Caire, 1978)."

  • Peromyscus eremicus photographed by Rick Overson and Laura Steger in the Peloncillo Mountains of southeastern Arizona.
  • Peromyscus eremicus photographed by Rick Overson and Laura Steger in the Peloncillo Mountains of southeastern Arizona.

Habitat

From Veal & Caire (1979): "Peromyscus eremicus is common in desert shrub and riparian habitats throughout the southwestern United States, north central Mexico, and Baja California."

Skull

From Johnson & Armstrong (1987): "Dental pattern simple, much like P. eremicus; accessory lophs typically absent; presence of accessory styles geographically variable; when present, unattached to neighboring cusps or lophs; no mesoloph; lower teeth simpler than upper teeth, no meso- or ectolophids, and stylids small and present in one-third of sample; details and frequency distributions of dental traits provided by Hooper (1957)."

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Similar species

From Veal & Caire (1979): "Peromyscus eremicus occurs sympatrically with four other species of the subgenus Haplomylomys (P. californicus, P. crinitus, P. eva, and P. merriami and with two members of the boylii species group (P. pectoralis and P. boylii). Because of broad overlap of species ranges and extensive geographic variation in most characters of P. eremicus and other species of Peromyscus, the diagnostic characters at one locality may not be diagnostic at another locality. To insure proper identification a combination of characters are needed."

From Hoffmeister (1986) for Arizona: "P. eremicus differs from P. boylii in less heavily haired and less bicolored tail, smaller ears, upper molars 1-2 without mesolophs. P. merriami is most similar to P. eremicus and differs from it usually in these features: mastoidal breadth more than 11.55 mm rather than less, greatest length of skull more than 25.75 mm rather than less, baculum curves ventrally rather than dorsally, length of baculum more than 8.5 mm rather than less. Other features include longer hind foot, usually 21.6 mm or more rather than less, total length greater, pectoral spot frequently present, underparts frequently cream-colored rather than whitish. P. crinitus is similar to and often confused with P. eremicus from which it differs as follows: tail with a covering of hairs so that annulations are less conspicuous and with a noticeable tuft of hairs at the tips. P. eremicus differs from P. maniculatus in actually and relatively longer tail, less heavily haired and less biocolored tail, body shorter rather than longer than tail, ears not fringed with white, and no white preauricular patch, upper molars 1-2 without mesolophs."

Comparison of the baculum of Peromyscus merriami and Peromyscus eremicus from Hoffmeister and Lee (1963).
Comparison of the skulls of Peromyscus merriami and Peromyscus eremicus as shown by Commissaris (1960). Hoffmeister and Lee (1963) found that "no single cranial character was found to be always diagnostic. Even the presence or absence of the exposed mastoid process, regarded by Commissaris as a qualitative character, was found to be unreliable in a great many cases."

References

Benson SB. 1933. Concealing coloration among some desert rodents of the southwestern United States. Univ. California Publ. Zool. 40:1-70.

Caire W. 1978. Distribution and zoogeography of the mammals of Sonora, Mexico. Ph.D. dissertation, University of New Mexico, Albuquerque.

Commissaris LR. 1960. Morphological and ecological differentiation of Peromyscus merriami from southern Arizona. Journal of Mammalogy 41(3):305-310.

Dice LR, Blossom PM. 1937. Studies of mammalian ecology in southwestern North America, with special attention to the colors of desert animals. Washington D.C. (USA): Carnegie Institution of Washington.

Hoffmeister DF. 1986. Mammals of Arizona. Tucson (AZ, USA): University of Arizona Press.

Hoffmeister DF, Lee MR. 1963. The status of the sibling species Peromyscus merriami and Peromyscus eremicus. Journal of Mammalogy 44(2):201-213.

Johnson DW, Armstrong DM. 1987. Peromyscus crinitus. Mammalian species (287):1-8.

Findley JS, Harris AH, Wilson DE, Jones C. 1975. Mammals of New Mexico. Albuquerque (NM, USA): University of New Mexico Press.

Koschmann JR. 1974. Melanism in rodents of the Afton lava flows, Dona Ana County. M.S. thesis, University of Texas at El Paso.

Ridde BR, Hafner DJ, Alexander LF. 2000. Phylogeography and systematics of the Peromyscus eremicus species group and the historical biogeography of North American warm regional deserts. Molecular Phylogenetics and Evolution 17:145–160.

Veal R, Caire W. 1979. Peromyscus eremicus. Mammalian species (118): pp.1-6.

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