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Reithrodontomys megalotis

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Western Harvest Mouse
(Reithrodontomys megalotis)
Range
Taxonomic classification
Order:Rodentia
Suborder:Supramyomorpha
Infraorder:Myomorphi
Superfamily:Muroidea
Family:Cricetidae
Subfamily:Neotominae
Tribe:Reithrodontomyini
Genus:Reithrodontomys
Subgenus:Reithrodontomys (subgenus)
Binomial details
Reithrodontomys megalotis (S. F. Baird, 1858)

Description

From Best & Hunt (2020): "This is a small mouse that is tan, brown, or brownish-gray dorsally and gray or gray washed with tan ventrally. Winter pelage is paler and longer than in summer. Ears are prominent. The tail is scaly, sparsely haired, indistinctly bicolored, and about the same length as head and body combined. Upper incisors are deeply grooved."

From Armstrong et al. (2010): "The western harvest mouse is similar to the plains harvest mouse but larger in size. Color ranges from buffy to grayish brown. A poorly defined mid-dorsal blackish wash is typical. The tail is bicolored, the dorsal stripe being half the width of the tail."

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
Arizona (Chino Valley, Yavapai Co.) Hoffmeister (1986) 126–145 (n=40) 57–77 (n=40) 17–20 (n=40) 14–16 (n=40)
Arizona (Cochise Co.) Hoffmeister (1986) 119–147 (n=99) 55–79 (n=99) 16–18 (n=99) 11–15 (n=99)
Arizona (No. Apache and Navajo cos.) Hoffmeister (1986) 127–140 (n=11) 55–68 (n=11) 16–18 (n=11) 13–15 (n=11)
Arizona (Stanfield and Casa Grande, Pinal Co.) Hoffmeister (1986) 127–150 (n=24) 64–84 (n=24) 16–18 (n=24) 12–17 (n=24)
Arizona (Surprise, Buckeye, Marinette, Maricopa Co.) Hoffmeister (1986) 122–152 (n=31) 61–78 (n=31) 16–18 (n=31) 12–17 (n=31)
Arizona (vicinity of Parker, Yuma Co.) Hoffmeister (1986) 125–146 (n=15) 62–81 (n=15) 17–19 (n=15) 14–16 (n=15)
Arizona (vicinity of Williams and Drake, Coconino Co.) Hoffmeister (1986) 125–154 (n=25) 60–76 (n=25) 17–20 (n=25) 13–15 (n=25)
Arizona (vicinity of Winslow, Navajo Co.) Hoffmeister (1986) 117–149 (n=71) 50–70 (n=71) 15–21 (n=71) 13–17 (n=71)
Arizona (vicinity Springerville, Apache Co.) Hoffmeister (1986) 118–156 (n=46) 57–83 (n=46) 16–19 (n=46) 13–16 (n=46)
Arizona (Wolf Hole, Diamond Butte, Mt. Trumbull, Mohave Co.) Hoffmeister (1986) 131–155 (n=18) 59–74 (n=18) 15–18 (n=18) 13–16 (n=18)
California Jameson & Peeters (2004) 114–145 50–70 15–18 12–15 9–14
Colorado Armstrong et al. (2010) 113–160 48–74 15–18 12–17 9–21
Minnesota Hazard (1982) 123–153 55–74 15–18 12–14 10.0–12.9 (n=6)
Nebraska Johnsgard (2020) 122–155 56–73 11–17
New Mexico (Four Corners and Mc Kinley Co.) Hoffmeister (1986) 124–151 (n=10) 57–75 (n=10) 16–18 (n=10) 13–15 (n=10)
North Dakota Seabloom et al. (2020) 136 62 16 12 12–15
not reported Ceballos (editor, 2014) 135–154 64 15–18 13–15 8–13
Texas Schmidly & Bradley (2016) 140 71 18 10–16


Skull

From Wilkins (1986): "Breadth of braincase is less than or equal to 9.6 mm in R . montanus; in R . megalotis, the braincase is broader than 9.5 mm. These species also differ in molar features, best seen in the first two upper molars (Hooper, 1952); in R. montanus, cusps are shorter and the principal labial enamel folds are broad and long so that the primary cusps seem farther apart than in R . megalotis. In lateral profile, regions between paracone and anterocone and between para cone and metacone are U-shaped in R . montanus but V-shaped in R . megalotis."

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Similar species

From King & McCain (2015): "Reithrodontomys megalotis and R. montanus, two species of harvest mouse that co-occur at low elevations of the southeastern Rockies and wester Great Plains, are notoriously difficult to distinguish both externally and cranially, particularly for juveniles."

From Best & Hunt (2020): "Plains harvest mice [Reithrodontomys montanus] are similar in appearance to western harvest mice, but the tail of the plains harvest mouse is shorter than the length of head and body combined, and its tail is more sharply bicolored than the tail of the western harvest mouse."

From Armstrong et al. (2010): "Rather difficult to distinguish from the western harvest mouse, plains harvest mice [Reithrodontomys montanus] are slightly smaller externally and cranially (greatest length of the skull is less than 21 mm, although the braincase is relatively broader), have a more pronounced mid-dorsal dark patch, and have a narrower tail stripe than the western harvest mouse. Generally the tail is equal to or shorter than the head and body in the plains harvest mouse and longer than the head and body in the western harvest mouse. Hoofer et al. (1999) distinguished troublesome species of R. megalotis and R. montanus by a combination of cranial measurements. From the deer mouse, harvest mice are readily distinguished by their grooved upper incisors."

From Wilkins (1986): "Reithrodontomys montanus and R . megalotis are similar in size, coloration, and cranial proportions, especially in the Great Plains region (Hooper, 1952). The tail is equal to or longer than the head and body in R . megalotis, whereas the tail is shorter than the head and body in R . montanus. The tail is more sharply bicolored in R . montanus (Schmidly, 1977)."

References

Armstrong DM, Fitzgerald JP, Meaney CA. 2010. Mammals of Colorado, Second Edition. Denver (CO, USA): University Press of Colorado.

Baird SF. 1855. Characteristics of Some New Species of North American Mammalia, Collected Chiefly in Connection with the U. S. Surveys of a Railroad Route to the Pacific. Proceedings of the Academy of Natural Sciences of Philadelphia 7, 335.

Best TL, Hunt JL. 2020. Mammals of the southeastern United States. Tuscaloosa (AL, USA): University Alabama Press.

Ceballos G, editor. 2014. Mammals of Mexico. Baltimore (MD, USA): Johns Hopkins University Press.

Hazard EB. 1982. The mammals of Minnesota. Minneapolis (MN, USA): University of Minnesota Press.

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

Hooper ET. 1952. A systematic review of the harvest mice (genus Reithrodontomys) of Latin America. Miscellaneous Publications of the Museum of Zoology, University of Michigan, 77: 1-255.

Johnsgard PA. 2020. Wildlife of Nebraska: a natural history. Lincoln (NE, USA): University of Nebraska Press.

King SR, McCain CM. 2015. Robust discrimination of Reithrodontomys megalotis and R. montanus (Mammalia: Rodentia) from Colorado, using cranial morphology and external characteristics within age classes. Proceedings of the Biological Society of Washington 128(1): 1-10.

Schmidly DJ. 1977. The mammals of Trans-Pecos Texas. College Station (TX, USA): Texas A&M University Press.

Seabloom R, Hoganson JW, Jensen WF. 2020. The mammals of North Dakota. Fargo (ND, USA): North Dakota State University Press.

Wilkins KT. 1986. Reithrodontomys montanus. Mammalian Species (257): 1-5.

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