Chaetodipus penicillatus

Desert Pocket Mouse
(*Chaetodipus penicillatus*)
Desert Pocket Mouse (Chaetodipus penicillatus)
Range
Taxonomic classification
Order:	Rodentia
Suborder:	Supramyomorpha
Infraorder:	Castorimorphi
Superfamily:	Geomyoidea
Family:	Heteromyidae
Subfamily:	Perognathinae
Genus:	Chaetodipus
Binomial details
	Chaetodipus penicillatus (S. W. Woodhouse, 1853)
Other resources
	Full taxonomic details at MDD

The Desert Pocket Mouse (Chaetodipus penicillatus) is a small- to medium-sized pocket mouse with a long tail. It is found in sandy soils in the Sonoran and Mojave Deserts.

Description

From Hoffmeister (1986): "Size medium to small; rump without spines or spine-like hairs; tail usually 10-20 mm longer than head-body; tail lightly pencillate; dorsal tail stripe slightly darker than rest of dorsum; dorsal coloration grayish or pinkish brown mixed with black and dark browns."

From Jameson & Peeters (2004): "A medium-sized pocket mouse with rather coarse, but not spiny, yellow gray pelage. Its tail is faintly bicolored, often annulated (ringed), with a conspicuous tuft and crest. The heel of the hind foot is naked. The ears are relatively pointed."

Museum specimens

Holotype: USNM 73881. Chaetodipus penicillatus angustirostris . Adult male. Carrizo Creek, Colorado Desert, [Imperial County], California. Collected 31 March 1895.
Holotype: USNM 73881. Chaetodipus penicillatus angustirostris . Adult male. Carrizo Creek, Colorado Desert, [Imperial County], California. Collected 31 March 1895.
ASUMAC008983. Chaetodipus penicillatus. Adult female. Big Horn Mountains, Maricopa County, Arizona. Collected 26 May 2023.

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)	153–221	91–121	21–27		14–20
not reported	Ceballos (editor, 2014)	162–216	83–129	22–27	7–10	16.5
not reported	Mantooth & Best (2005)	males: 167.7 (n=20); females: 167.3 (n=20)	males: 91.1 (n=20); females: 91.5 (n=20)	males: 21.6 (n=20); females: 23.1 (n=20)	males: 8.2 (n=20); females: 8.5 (n=20)	16.89

Skull

From Hoffmeister (1986): "interparietal five-sided and anterior edge angled; extension of anterior wings of supraoccipital, between interparietal and bullae, truncate; mastoid bullae small... interorbital breadth less than interparietal breadth."

Holotype: USNM 73881. Chaetodipus penicillatus angustirostris . Adult male. Carrizo Creek, Colorado Desert, Imperial County, California. Collected 31 March 1895. Dorsal view of the skull.
Holotype: USNM 73881. Chaetodipus penicillatus angustirostris . Arrows identify the interorbital width. The interparietal bone is colored yellow.
Holotype: USNM 73881. Chaetodipus penicillatus angustirostris . Adult male. Carrizo Creek, Colorado Desert, Imperial County, California. Collected 31 March 1895. Dorsal view of the skull.
Holotype: USNM 73881. Chaetodipus penicillatus angustirostris . Adult male. Carrizo Creek, Colorado Desert, Imperial County, California. Collected 31 March 1895. Ventral view of the skull.
Holotype: USNM 73881. Chaetodipus penicillatus angustirostris . Adult male. Carrizo Creek, Colorado Desert, Imperial County, California. Collected 31 March 1895. Dorsal view of the mandible.
Holotype: USNM 73881. Chaetodipus penicillatus angustirostris . Adult male. Carrizo Creek, Colorado Desert, Imperial County, California. Collected 31 March 1895. Lateral view of the left mandible.
Holotype: USNM 73881. Chaetodipus penicillatus angustirostris . Adult. Upper molars.
Holotype: USNM 73881. Chaetodipus penicillatus angustirostris . Adult. Lower molars.
NEON05FZV. The interparietal of Chaetodipus penicillatus is pentagonal with all angles somewhat rounded and does not contact the mastoid bullae (Hall, 1981; Mantooth and Best, 2005).

Similar species

In the USA, Chaetodipus penicillatus is sympatric or near-sympatric with the following species of pocket mice: Bailey's Pocket Mouse (Chaetodipus baileyi), California Pocket Mouse (Chaetodipus californicus),Chihuahuan Desert Pocket Mouse (Chaetodipus eremicus), San Diego Pocket Mouse (Chaetodipus fallax), Long-tailed Pocket Mouse (Chaetodipus formosus), Hispid Pocket Mouse (Chaetodipus hispidus), Rock Pocket Mouse (Chaetodipus intermedius), Peninsular Pocket Mouse (Chaetodipus rudinoris), Spiny Pocket Mouse (Chaetodipus spinatus), White-eared Pocket Mouse (Perognathus alticolus), Arizona Pocket Mouse (Perognathus amplus), Silky Pocket Mouse (Perognathus flavus), Little Pocket Mouse (Perognathus longimembris), and Great Basin Pocket Mouse (Perognathus mollipilosus).

Comparison with Chaetodipus baileyi

From Hoffmeister (1986): "penicillatus (large specimens) is sometimes confused with and difficult to distinguish of 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.

Desert Pocket Mouse (Chaetodipus penicillatus)
Bailey's Pocket Mouse (Chaetodipus baileyi)
Holotype: 73881. Chaetodipus penicillatus angustirostris . Black arrows identify the interorbital width. The interparietal bone is colored yellow. The interorbital breadth is less than the interparietal breadth.
Holotype: 17838/24775. Chaetodipus baileyi baileyi. Black arrows identify the interorbital width. The interparietal bone is colored yellow. The interorbital breadth is greater than the interparietal breadth.

Comparison with Chaetodipus californicus

The California Pocket Mouse (Chaetodipus californicus) differs from Chaetodipus penicillatus in its generally larger size, numerous stiff spines on the rump, the sharply evident buff-colored lateral line separating the dorsal pelage from the white venter, and the interparietal width being noticeably greater than the interorbital width (Patton and Alvarez-Castañeda, 1999).

Desert Pocket Mouse (Chaetodipus penicillatus)
California Pocket Mouse (Chaetodipus californicus)
Holotype: 73881. Chaetodipus penicillatus angustirostris . Black arrows identify the interorbital width. The interparietal bone is colored yellow.
Holotype: 32116/43928. Chaetodipus californicus dispar. Arrows identify the interorbital width. The interparietal bone is colored yellow. The interparietal width is noticeably greater than the interorbital width.

Comparison with Chaetodipus eremicus

Desert Pocket Mouse (Chaetodipus penicillatus)
Chihuahuan Desert Pocket Mouse (Chaetodipus eremicus)
Holotype: 73881. Chaetodipus penicillatus angustirostris . Arrows identify the interorbital width. The interparietal bone is colored yellow.
Holotype: 21052/36094. Chaetodipus eremicus eremicus. Adult female. Arrows identify the interorbital width. The interparietal bone is colored yellow.

Comparison with Chaetodipus fallax

The San Diego Pocket Mouse (Chaetodipus fallax) differs from Chaetodipus penicillatus in having spiny hairs on the rump and flanks.

Desert Pocket Mouse (Chaetodipus penicillatus) observed in the Peloncillo Mountains of Arizona by Rick Overson and Laura Steger.
San Diego Pocket Mouse (Chaetodipus fallax) observed by Alyssa Semerdjian in Rancho Jamul Ecological Reserve, San Diego County, California. Black arrows point to one of each of the many white and black spiny hairs.

Comparison with Chaetodipus formosus

In the Long-tailed Pocket Mouse (Chaetodipus formosus), the interorbital width is greater than the interparietal, whereas in Chaetodipus penicillatus the interorbital breadth is less than the interparietal breadth (Hoffmeister, 1986).

Long-tailed Pocket Mouse (Chaetodipus formosus)
Desert Pocket Mouse (Chaetodipus penicillatus)
Holotype: 186508. Chaetodipus formosus formosus. Arrows identify the interorbital width. The interparietal bone is colored yellow. The interorbital width is greater than the interparietal width (Hoffmeister, 1986).
Holotype: 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 Chaetodipus hispidus

Hispid Pocket Mouse (Chaetodipus hispidus) differs from Chaetodipus penicillatus in larger size, well-defined lateral line, and tail that lacks a crest or tuft.

Desert Pocket Mouse (Chaetodipus penicillatus). This is a medium-sized pocket mouse with a tail that has both a crest and tuft. Dorsal coloration generally ranges from gray to yellowish-brown to pinkish-brown.
Hispid Pocket Mouse (Chaetodipus hispidus). This is a large pocket mouse. Dorsal coloration generally ranges from yellowish to reddish-buff. The tail lacks a crest and tuft.

Comparison with Chaetodipus intermedius

From Hoffmeister (1986): "[Chaetodipus] intermedius differs from [Chaetodipus] penicillatus, the species with which it is most frequently confused, in the presence of spinelike hairs on the rump; hind foot usually 22 mm or less rather than more; interparietal with straight rather than angled suture along anterior face, and thus not pentagonal or five-sided; extensions of anterior wings of supraoccipital between interparietal, and bullae wedge-shaped rather than truncate; rostrum narrower."

Desert Pocket Mouse (Chaetodipus penicillatus)
Rock Pocket Mouse (Chaetodipus intermedius)
The interparietal of the Desert Pocket Mouse (Chaetodipus penicillatus) is pentagonal with all angles somewhat rounded and does not contact the mastoid bullae (Hall, 1981; Mantooth and Best, 2005).
Rock Pocket Mouse (Chaetodipus intermedius). The interparietal (in yellow) is not in contact with the bullae and is separated by narrow projections of parietals and supraoccipitals. Black arrows point to the narrow projections of the supraoccipitals in blue. The narrow projections of the parietals are shown in green. The anterior edge of the interparietal nearly straight, not angled forward.

Comparison with Chaetodipus rudinoris

The Peninsular Pocket Mouse (Chaetodipus rudinoris) differs from Chaetodipus penicillatus in its larger size and the interorbital region is usually equal to or wider than the width of the interparietal. Chaetodipus rudinoris was considered a subspecies of Chaetodipus baileyi until 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, Chaetodipus rudinoris.

Desert Pocket Mouse (Chaetodipus penicillatus) observed in the Peloncillo Mountains of Arizona by Rick Overson and Laura Steger.
Peninsular Pocket Mouse (Chaetodipus rudinoris) observed by Alan Harperin Baja California Sur, Mexico. Dorsal coloration varies from yellowish-gray to buffy ochre or pale buffy.
Holotype: 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)
Holotype: 146672. Chaetodipus rudinoris extimus. Adult female. Arrows point to the interorbital width. The interparietal bone is colored yellow. The interorbital region is usually equal to or wider than the width of the interparietal.

Comparison with Chaetodipus spinatus

The Spiny Pocket Mouse (Chaetodipus spinatus) differs from Chaetodipus penicillatus in the presence of large and prominent spines on the rump, scattered on the flanks and sides, and often extending to the shoulders (Lackey, 1991).

Desert Pocket Mouse (Chaetodipus penicillatus) observed in the Peloncillo Mountains of Arizona by Rick Overson and Laura Steger.
Spiny Pocket Mouse (Chaetodipus spinatus) photographed by Charles A. Drost and Jan Hart, USGS. The pelage of C. spinatus is hispid, with large and prominent spines on the rump, scattered on the flanks and sides, and often extending to the shoulders (Lackey, 1991).

Comparison with pocket mice in the genus Perognathus

In the USA, Chaetodipus penicillatus is sympatric with the White-eared Pocket Mouse (Perognathus alticolus), Arizona Pocket Mouse (Perognathus amplus), Silky Pocket Mouse (Perognathus flavus), Little Pocket Mouse (Perognathus longimembris), and Great Basin Pocket Mouse (Perognathus mollipilosus). However, these species are small pocket mice with smooth tails that lack obvious crests or tufts.

Desert Pocket Mouse (Chaetodipus penicillatus)
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.
Great Basin Pocket Mouse (Perognathus mollipilosus) from Tooele County, Utah. Collected 28 April 2023.
White-eared Pocket Mouse (Perognathus alticolus) observed by Venkat Sankar in Kern County, California.
Holotype: 99828. Perognathus longimembris bangsi. Adult male. San Felipe Narrows, San Diego County, California. Collected 11 April 1892.

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.

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

Mantooth SJ, Best TL. 2005. Chaetodipus penicillatus. Mammalian Species (767): 1-7. https://doi.org/10.2307/3504532

Osgood WH. 1900. Revision of the pocket mice of the genus Perognathus. North American Fauna 18:1-73.

Williams DF, Genoways HH, Braun JK. 1993. Taxonomy and systematics. Pp. 38-196 in Biology of the Heteromyidae (H. H. Genoways and J. H. Brown, eds.). Special Publication, The American Society of Mammalogists 10:1-719.

Woodhouse SW. 1852. Description of a new species of pouched rat, of the genus Perognathus, Wied. Proceedings of the Academy of Natural Sciences of Philadelphia 6:200-201.