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Peromyscus gratus

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Saxicoline Deermouse
(Peromyscus gratus)
Range
Taxonomic classification
Order:Rodentia
Suborder:Supramyomorpha
Infraorder:Myomorphi
Superfamily:Muroidea
Family:Cricetidae
Subfamily:Neotominae
Tribe:Peromyscini
Genus:Peromyscus
Binomial details
Peromyscus gratus Merriam, 1898

Description

From Ceballos (ed., 2014) for Mexico: "Peromyscus gratus is a medium-sized mouse that can possess three types of coloration: light gray slightly mixed with yellowish on a gray background, ochraceous slightly mixed with brown on a gray background, or brown slightly mixed with ochraceous on a gray background (Ceballos and Galindo, 1984; Hernández, 1990). It has a lateral line of buffy coloration. The legs are white. The tail is bicolored, brown above and whitish below. The ears are very large, a feature that distinguishes it from P. maniculatus, P. melanotis, and P. aztecus (Anderson, 1972; Ceballos and Galindo, 1984; Chávez, 1993; Goodwin, 1969; Hernández, 1990)."

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, New Mexico Diersing (2023) head and body: 75–106 (n=45) 77–111 (n=41) 20.5–25 (n=46) 19–25 (n=28)
Mexico (Chihuahua) Diersing (2023) head and body: 80–105 (n=55) 86–111 (n=43) 21–24 (n=55) 20–28 (n=55)
not reported Ceballos (editor, 2014) 171–231 76–123 20–27 18–25 20–33


Skull

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Species comparisons

Comparison with Peromyscus boylii

From Diersing (2023): "Peromyscus gratus from P. boylii—Greatest skull length of the two species averages about the same, but P. gratus is, on average, much broader in braincase breadth (12.74 vs. 12.27 mm) and mastoidal breadth (12.11 vs. 11.53 mm). Size measurements of the auditory bullae are the best characters for distinguishing the two species. Bulla length averages 3.65 mm in P. gratus compared with 3.30 mm in P. boylii. In bullae breadth, P. gratus averages 9.38 mm (range of 9.00–9.80 mm) and P. boylii averages 8.60 mm (range of 7.95–8.95 mm), with no overlap between the two samples. Head and body length and tail length are similar in the two species. Hind foot length and ear length are about equal in P. gratus (22.6 and 22.5 mm, respectively), whereas in P. boylii hind foot length is much longer than ear length (21.6 and 19.7 mm)."

Comparison with Peromyscus nasutus

From Diersing (2023): "Peromyscus gratus from P. nasutus—Greatest skull length in P. gratus is ≤27.75 mm in 91% (42 of 46) of specimens [examined] and ≥27.80 mm in 85% (33 of 39) [examined] of P. nasutus. Compared with P. nasutus, P. gratus averages slightly larger auditory bullae (3.65 vs. 3.44 mm) and markedly shorter maxillary toothrows (3.93 vs. 4.28 mm). In P. gratus, maxillary toothrow length is slightly longer than bulla length (in 98% [examined], toothrow length is 0.55 mm longer than bulla length). In P. nasutus, maxillary toothrow length is much longer than bulla length (in 92% [examined], toothrow length is ≥0.6 mm longer than bulla length). In external measurements, P. gratus has a much shorter tail (average of 94.21 vs. 108.83 mm) and hind foot length is about equal to ear length (average of 22.6 and 22.5 mm, respectively), whereas in P. nasutus hind foot length is much longer than ear length (23.6 and 21.6 mm)."

Comparison with Peromyscus truei

From Diersing (2023): "Peromyscus gratus from P. truei—The best two skull features for distinguishing P. gratus from P. truei in New Mexico and Arizona are bulla length and bullae breadth. All 46 specimens [examined] of P. gratus have bulla length of 3.80 mm, whereas 86 of 88 [examined] P. truei are ≥3.90 mm. For bullae breadth, 45 of 46 specimens [examined] of P. gratus have bullae breadth of ≤9.70 mm and 83 of 88 [examined] P. truei are ≥9.80 mm. For those few specimens that overlap in these two measurements, length of the incisive foramen (short in P. truei, particularly short relative to diastema length, and the opposite in P. gratus) and postpalatal length and greatest skull length will separate other specimens. For external body measurements, P. gratus has a slightly shorter head and body length, slightly longer tail, slightly shorter hind foot, and much shorter ears (22.5 vs. 24.9 mm, 25.2 mm, and 25.5 mm in P. truei samples 1, 2, and 3a, respectively)."

Distribution notes

From Diersing (2023): "Hoffmeister (1986) reported two specimens of P. truei from Greenlee County, Arizona (USNM 205510 and 205613). Both are referable to P. gratus. Careful examination of other species similar to P. gratus in collections could reveal additional specimens of P. gratus from the southwestern United States. Likewise, future collecting, particularly in Hidalgo County, would be helpful in documenting the current status of this species along the United States–Mexico border. Because this study correctly identified the specimen of P. gratus that Diersing (1976) believed to be P. nasutus from Hidalgo County, the distribution of P. gratus and P. nasutus in the United States is nonoverlapping and closely complementary."

References

Anderson S. 1972. Mammals of Chihuahua: taxonomy and distribution. Bulletin of the American Museum of Natural History v. 148, article 2.

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

Ceballos G, Galindo C. 1984. Mamiferos silvestres de la Cuenca de Mexico. Editorial. Limusa, Mexico, Distrito Federal, Mexico.

Chávez JC. 1993. Dinámica poblacional y uso de hábitat por roedores en un matorral de palo loco (Senecio praecox). Bachelor thesis, Facultad de Ciencias, Universidad Nacional Autonoma de México.

Diersing VE. 1976. An analysis of Peromyscus difficilis from the Mexican–United States boundary area. Proceedings of the Biological Society of Washington 89:451–466.

Diersing VE. 2023. Merriam's Pinyon Mouse, Peromyscus gratus, in the United States: Distribution and Recognition. The Southwestern Naturalist 67(4): 244-254.

Goodwin GG. 1969. Mammals from the State of Oaxaca, Mexico, in the American Museum of Natural History. Bulletin of the American Museum of Natural History v. 141, article 1.

Hernández-Chávez JJ. 1990. Taxonomia y distribucion del genero Peromyscus (Rodentia: Cricetidae) en el Estado de Mexico, Mexico. Tesis de Licenciatura Escuela Nacional de Ciencias Biologicas, IPN.

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

Merriam CH. 1898. Descriptions of twenty new species and a new subgenus of Peromyscus from Mexico and Guatemala. Proceedings of the Biological Society of Washington 12:115–125.

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