Chaetodipus baileyi

Bailey's Pocket Mouse
(*Chaetodipus baileyi*)
Bailey's Pocket Mouse (Chaetodipus baileyi)
Range
Taxonomic classification
Order:	Rodentia
Suborder:	Supramyomorpha
Infraorder:	Castorimorphi
Superfamily:	Geomyoidea
Family:	Heteromyidae
Subfamily:	Perognathinae
Genus:	Chaetodipus
Binomial details
	Chaetodipus baileyi (C. H. Merriam, 1894)
Other resources
	Full taxonomic details at MDD

Bailey's Pocket Mouse (Chaetodipus baileyi) is a large pocket mouse with a long, well-haired tail. It can be found in a variety of arid habitats in Arizona, New Mexico, and the Mexican states of Sonora, Sinaloa, and Chihuahua.

Description

From Paulson (1988): "The pelage above is grayish, washed to a varying degree with yellow, and is somewhat harsh; underparts are whitish."

From Patton and Alvarez-Castañeda (editors, 1999): "Chaetodipus baileyi is one of the largest species in the genus, with total length usually more than 200 [mm] and a hind foot usually greater than 26 [mm]. It lacks stiff rump spines, has a soft yellowish gray-brown dorsal pelage color and a self-colored white venter. The ears are moderately large, usually greater than 9 mm; the tail is long, strongly crested, and buff to gray above, whitish below."

From Hoffeister (1986): "If color is used as a comparative feature, it must be used cautiously. Subadults or juveniles often are much paler than adults. Exceedinlgy old animals also take on paler or "grayed" appearance in many cases." Additionally, "there is a group of dark-colored populations in eastern Arizona, lighter colored populations centrally, and palest populations to the west."

Ears have a lobed antitragus (projection of flesh in the lower inner part of the ear).

Museum type specimens

Holotype: USNM 17838/24775. Chaetodipus baileyi baileyi. Adult female. Magdalena, Sonora, Mexico. Collected 3 November 1889.
Holotype: USNM 17838/24775. Chaetodipus baileyi baileyi. Adult female. Magdalena, Sonora, Mexico. Collected 3 November 1889.

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 (Cochise County, San Bernardino Ranch)	Hoffmeister (1986)	body length: 98.5 (males, n=16) and 92.0 (females, n=7)		males: 28.9 (n=16); females: 29.0 (n=7)
Arizona (Gila County, vicinity of Roosevelt)	Hoffmeister (1986)	body length: 99.7 (males, n=27) and 92.8 (females, n=18)		males: 28.31 (n=27); females: 27.69 (n=18)
Arizona (Pima County, Baboquivari Mts.)	Hoffmeister (1986)	body length: 94.9 (males, n=15) and 91.9 (females, n=13)		males: 29.7 (n=15); females: 27.8 (n=13)
Arizona (Pima County, vicinity of Arivaca)	Hoffmeister (1986)	body length: 99.9 (males, n=12) and 98.6 (females, n=11)		males: 28.14 (n=12); females: 26.9 (n=11)
Arizona (Pinal County, Superior, Hayden)	Hoffmeister (1986)	body length: 96.9 (males, n=28) and 92.88 (females, n=26)		males: 27.78 (n=28); females: 26.98 (n=26)
Arizona (Yuma County, Castle Dome, Harquahala, Kofa Mts.)	Hoffmeister (1986)	body length: 99.14 (males, n=7) and 95.42 (females, n=12)		males: 27.86 (n=7); females: 25.67 (n=12)
not reported	Ceballos (editor, 2014)	188–223	103–124	24–27	7–11	24–28

Skull

From Hoffmeister (1986): "interorbital region wider than width of interparietal; toothrow long (alveolar length of maxillary toothrow always 4.0 mm or more)."

Holotype: USNM 17838/24775. Chaetodipus baileyi baileyi. Adult female. Magdalena, Sonora, Mexico. Collected 3 November 1889. Dorsal view of the skull.
Holotype: USNM 17838/24775. Chaetodipus baileyi baileyi. Arrows identify the interorbital width. The interparietal bone is colored yellow. The interorbital width is usually equal to or greater than the width of the interparietal (Hoffmeister, 1986).
Holotype: USNM 17838/24775. Chaetodipus baileyi baileyi. Adult female. Magdalena, Sonora, Mexico. Collected 3 November 1889. Lateral view of the left mandible.
Holotype: USNM 17838/24775. Chaetodipus baileyi baileyi. Adult female. Magdalena, Sonora, Mexico. Collected 3 November 1889. Lateral view of the skull.
Holotype: USNM 17838/24775. Chaetodipus baileyi baileyi. Adult female. Magdalena, Sonora, Mexico. Collected 3 November 1889. Ventral view of the skull.
Holotype: USNM 17838/24775. Chaetodipus baileyi baileyi. Adult female. Magdalena, Sonora, Mexico. Collected 3 November 1889. Dorsal view of the mandible.
Holotype: USNM 17838/24775. Chaetodipus baileyi baileyi. Adult female. Upper molars shown.
Holotype: USNM 17838/24775. Chaetodipus baileyi baileyi. Adult female. Lower molars shown.

Taxonomic notes

Riddle et al. (2000) examined phylogenetic relationships within Chaetodipus baileyi and concluded that populations west of the Colorado River and Sea of Cortez should be recognized as a distinct species, the Peninsular Pocket Mouse (Chaetodipus rudinoris).

Similar species

In the USA, Chaetodipus baileyi is sympatric or near-sympatric with the following species of pocket mice: Chihuahuan Desert Pocket Mouse (Chaetodipus eremicus), Hispid Pocket Mouse (Chaetodipus hispidus), Rock Pocket Mouse (Chaetodipus intermedius), Desert Pocket Mouse (Chaetodipus penicillatus), Arizona Pocket Mouse (Perognathus amplus), and Silky Pocket Mouse (Perognathus flavus). From Patton and Alvarez-Castañeda (editors, 1999): "This species can readily be distinguished from all sympatric or near-sympatric chaetodipine [members of the genus Chaetodipus] pocket mice by the combination of its large size and lack of evident stiff rump spines. Confusion is really only possible between baileyi and C. penicillatus in Arizona and Sonora... but, again, baileyi is significantly larger in most dimensions of the body and skull."

Comparison with Chaetodipus eremicus

The Chihuahuan Desert Pocket Mouse (Chaetodipus eremicus) differs from Chaetodipus baileyi in smaller size and the interorbital region of the skull being narrower than the width of the interparietal, instead of the reverse in baileyi.

Bailey's Pocket Mouse (Chaetodipus baileyi)
Chihuahuan Desert Pocket Mouse (Chaetodipus eremicus).
Holotype: USNM 17838/24775. Chaetodipus baileyi baileyi. Arrows identify the interorbital width. The interparietal bone is colored yellow. The interorbital width is usually equal to or greater than the width of the interparietal (Hoffmeister, 1986).
Holotype: USNM 21052/36094. Chaetodipus eremicus eremicus. Arrows identify the interorbital width. The interparietal bone is colored yellow. The interorbital region is narrower than the width of the interparietal.

Comparison with Chaetodipus hispidus

From Patton and Alvarez-Castañeda (editors, 1999): "It is nearly the same size as C. hispidus in southeastern Arizona, but differs by its long and crested tail and grayish, instead of yellowish brown dorsal coloration."

Bailey's Pocket Mouse (Chaetodipus baileyi)
Hispid Pocket Mouse (Chaetodipus hispidus)

Comparison with Chaetodipus intermedius

From Hoffmeister (1986): "C. intermedius differs from C. baileyi in rump spines present; hind foot shorter (less than 26 mm); body shorter; interorbital breadth less than interparietal breadth; skull shorter and narrower; skull less deep (under 10.0 mm)." Additionally, C. intermedius is "strongly restricted to rocks and rocky habitats, mostly in the creosote bush-saltbush desertscrub. Without a rocky situation, intermedius should not be expected." The color of the dorsum in intermedius can vary based on the color of substrate.

Bailey's Pocket Mouse (Chaetodipus baileyi)
Rock Pocket Mouse (Chaetodipus intermedius)
Holotype: USNM 17838/24775. Chaetodipus baileyi baileyi. Arrows identify the interorbital width. The interparietal bone is colored yellow. The interorbital width is usually equal to or greater than the width of the interparietal (Hoffmeister, 1986).
Holotype: USNM 203003. Chaetodipus intermedius phasma. Arrows identify the interorbital width. The interparietal bone is colored yellow. The interparietal with is greater than the interorbital width (Hoffmeister, 1986).

Comparison with Chaetodipus penicillatus

From Hoffmeister (1986): "penicillatus (large specimens) is sometimes confused with and difficult to distinguish from baileyi. C. penicillatus in general is smaller than C. baileyi, with smaller body, shorter hind feet, and smaller skulls." Hoffmeister (1986) noted that characters useful for distinguishing C. penicillatus from C. baileyi are: hind foot usually 26 mm or less in C. penicillatus, whereas the hind foot is usually 27 mm or more in males in C. baileyi; interorbital breadth less than interparietal breadth in C. penicillatus, whereas in C. baileyi the interorbital width usually equal to or greater than interparietal width; the depth of the skull is usually 9.65 mm or less in C. penicillatus, whereas in baileyi the depth of the skull is 10.2 mm or more; the distance across maxillary toothrow (measured from the outside of right M1 to outside left M1) usually 4.9 mm or less, whereas in C. baileyi the distance across maxillary toothrow is usually 5.0 mm or more.

Bailey's Pocket Mouse (Chaetodipus baileyi)
Desert Pocket Mouse (Chaetodipus penicillatus).
Holotype: USNM 17838/24775. Chaetodipus baileyi baileyi. Arrows identify the interorbital width. The interparietal bone is colored yellow. The interorbital width is usually equal to or greater than the width of the interparietal (Hoffmeister, 1986).
Holotype: USNM 73881. Chaetodipus penicillatus angustirostris . Arrows identify the interorbital width. The interparietal bone is colored yellow. The interorbital breadth is less than the interparietal breadth (Hoffmeister, 1986).

Comparison with pocket mice in the genus Perognathus

In the USA, Chaetodipus baileyi is sympatric with the Arizona Pocket Mouse (Perognathus amplus) and the Silky Pocket Mouse (Perognathus flavus). However, these species are small pocket mice with smooth tails that lack obvious crests or tufts. The skulls of these two species of Perognathus have larger auditory bullae and a smaller interparietal bone than compared to Chaetodipus baileyi.

Bailey's Pocket Mouse (Chaetodipus baileyi)
Arizona Pocket Mouse (Perognathus amplus). Coloration varies among subspecies but, in general, it is salmon-ochre on the back and yellowish-white on the abdomen.
Silky Pocket Mouse (Perognathus flavus). Fur color varies depending on the subspecies and geographic location but typically ranges from yellowish-brown to grayish-brown.
Holotype: USNM 17838/24775. Chaetodipus baileyi baileyi. Adult female. Magdalena, Sonora, Mexico. Collected 3 November 1889. Dorsal view of the skull.
Holotype: USNM 212780. Perognathus amplus amplus. Adult male. Congress Junction, Yavapai County, Arizona. Collected 21 June 1916. Dorsal view of the skull.
Holotype: USNM 168650. Perognathus flavus piperi. Adult male. Southwest of Newcastle, Weston County, Wyoming. Collected 25 May 1910. Dorsal view of the skull.

References

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

Hall ER. 1981. The mammals of North America. 2 vols. John Wiley and Sons, New York.

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

Ingles LG. 1947. Mammals of California and its coastal waters. Stanford (CA, USA): Stanford University Press.

Jameson EW, Peeters HJ. 2004. Mammals of California (No. 66). Berkeley (CA, USA): University of California Press.

Merriam CH. 1894. Descriptions of Eight New Pocket Mice (Genus Perognathus). Proceedings of the Academy of Natural Sciences of Philadelphia 46, 262.

Patton JL, Alvarez-Castañeda ST, editors. 1999. Family Heteromyidae. Mamiferos del noroeste de México. La Paz (Baja California Sur, MX): Centro de Investigaciones Biológicas del Noroeste.

Riddle BR, Hafner DJ, Alexander LF. 2000. Comparative phylogeography of Baileys' pocket mouse (Chaetodipus baileyi) and the Peromyscus eremicus species group: historical vicariance of the Baja California peninsular desert. Molecular Phylogenetics and Evolution 17(2): 161-172.