Chaetodipus penicillatus (Woodhouse, 1852)

Don E. Wilson, Thomas E. Lacher, Jr & Russell A. Mittermeier, 2016, Heteromyidae, Handbook of the Mammals of the World – Volume 6 Lagomorphs and Rodents I, Barcelona: Lynx Edicions, pp. 170-233 : 216

37.

Desert Pocket Mouse

Chaetodipus penicillatus

French: Souris-a-abajoues du désert / German: \Wiisten-Rauhaartaschenmaus / Spanish: Raton de abazones de desierto

Other common names: Sonoran Desert Pocket Mouse

Taxonomy. Perognathus penecillatus sic] Woodhouse, 1852 ,

“New Mexico, west of Rio Grande.” Redesignated by D. F. Hoff meister and M. R. Lee in 1967 to “1 mi. SW Parker, Yuma Co., Arizona,” USA.

Based on detailed sequencing of nDNA and mtDNA genes, C. penicillatus is a close relative of C. eremicus , which was formerly considered conspecific. The two species are next closely related to C. pernix , all of which are part of the continental lineage of the “modern” clade of coarse-haired pocket mice, along with C. intermedius , C. nelsoni (including C. lineatus ), C. goldmani , and C. artus . Mitochondrial sequence analysis identified two major phyletic units within C. penicillatus roughly centered in the Mojave and Sonoran deserts that broadly overlap along the lower Colorado River (approximate distribution of the subspecies penicillatus , with FN =54). The Sonoran clade includes price, southern angustirostris, and most likely seri, with FN = 48; the northern clade includes sobrinus, stephensi , and the northern (western Mojave) angustirostris. Chromosomal complement of the Mojave clade has not been described. This distribution is concordant with morphological and allozyme patterns. Six subspecies recognized.

Subspecies and Distribution.

C.p.penicillatusWoodhouse,1852—SWUSA(SW&SCArizona).

C.p.angustirostrisOsgood,1900—SWUSAandNWMexico(SCCaliforniaandNEBajaCalifornia).

C.p.priceJ.A.Allen,1894—SWUSAandNWMexico(SArizona,SWNewMexico,andSonora).

C.p.seriNelson,1912—NWMexico(TiburonI,GulfofCalifornia,Sonora).

C.p.sobrinusGoldman,1939—SWUSA(SENevada,SWUtah,andNWArizona).

C. p. stephensi Merriam, 1894 — SW USA (EC California).

Descriptive notes. Head-body 79-87 mm, tail 83-129 mm, ear 7-10 mm, hindfoot 22-27 mm; weight 15-19 g. There is no significant secondary sexual dimorphism. The insular subspecies (seri) is somewhat smaller. The Desert Pocket Mouse is smooth-haired, small-sized for the genus, with crested and tufted tail longer than head-body length, and small ears. Relatively soft pelage is usually lacking spines on rump, and if present, these are rather inconspicuous, small, and not as stiff compared with those of coarse-haired species. Pelage is yellowish brown to yellowish gray, mixed with light and dark hairs; there is no lateral stripe, under parts are white, and post-auricular patch is only slightly lighter than dorsum. Chromosomal complement has 2n = 46 and FN = 48 or 54. The Desert Pocket Mouse occurs with three other very similar, smooth-haired species of pocket mice at the edges ofits distribution: in south-western New Mexico with its close relative, the Chihuahuan Desert Pocket Mouse ( C. eremicus ); in north-eastern Baja California with the Little Desert Pocket Mouse ( C. arenarius ); and in southern Sonora with the Sinaloan Pocket Mouse (C. pernix ). The Chihuahuan Desert Pocket Mouse has shorter tail length but is larger in most external and cranial measurements;it has lighter, more mottled pelage, with less sharply defined lateral line and more prominent post-auricular patch. The Little Desert Mouse is, on average, smaller; interorbital breadth is more than 25-8% of the occipitonasal length (vs. less than 25%); and dorsal pelage is uniform smoke gray (vs. yellowish-brown). Tail of the Sinaloan Pocket Mouse is thinly haired with a small crest. Hybridization without introgression with this last species was reported at one locality in agriculturally disturbed habitat in southern Sonora. Hybrids with 2n = 49, intermediate between that of the two species, and female hybrids had significantly fewer placental scars, suggesting that hybrids were partially or completely sterile. In its distribution in the Sonoran and Mojave Desert, the Desert Pocket Mouse is sometimes captured on the same trap lines as eight other species of coarse-haired pocket mice. The Peninsular Pocket Mouse ( C. rudinoris ) and Bailey’s Pocket Mouse ( C. baileyi ) are larger (hindfoot length longer than 25 mm) and more often occur on pebbly soils that mark transitions from sandy flats to rocky alluvial slopes or “bajadas.” The Hispid Pocket Mouse (C. hispidus ) is associated with desert grassland, is larger, and has short, non-crested and nontufted tail, and coarse pelage thatis olive buff with a distinctive ocherouslateral stripe. The Long-tailed Pocket Mouse (C. formosus ) has brownish, rather than yellowish, pelage and, like the San Diego Pocket Mouse ( C. fallax ), the Spiny Pocket Mouse ( C. spinatus ), the Rock Pocket Mouse, and Goldman'’s Pocket Mouse ( C. goldmani ), occurs on gravelly or rocky soils but not in sandy soils to which the Desert Pocket Mouse is restricted. The latter four species all possess conspicuous rump spinesto various degrees.

Habitat. Restricted to sandy soils throughout the Sonoran Desert and parts of the MoJjave Desert, at elevations of 36-1585 m. The Desert Pocket Mouse displays a strong affinity for areas with creosote bush ( Larrea , Zygophyllaceae ) and saltbush ( Atriplex , Amaranthaceae ). It also occurs in association with catclaw ( Acacia , Fabaceae ), blue grama ( Bouteloua , Poaceae ), tarbush ( Flourensia , Asteraceae ), ocotillo ( Fouquieria , Fouquieriaceae ), cholla ( Opuntia , Cactaceae ), mesquite ( Prosopis , Fabaceae ), and yucca ( Yucca , Asparagaceae ). It usually occurs on mostly level terrain. On Tiburon Island,it occurs on gently sloping hills and flat areas where soils consist of sand and gravel. Burrows of Desert Pocket Mice are found around bases of bushes or in the open, and they include nest chamber, seed caches, and usually multiple openings.

Food and Feeding. Diet of the Desert Pocket Mouse consists largely of seeds of shrubs, annuals, and grasses, butit also includes smaller amounts of green vegetation and insects. Potentially poisonous seeds ofjojoba ( Simmondsia chinensis, Simmondsiaceae ) are refused in captivity, even when facing starvation. Foraging activity fluctuates with availability of seeds. Normally a ground forager, the Desert Pocket Mouse will climb vegetation to collect food. Food items are collected in external, fur-lined cheek pouches and transported back to burrows, where they are stored in burrow caches. It does not need to drink water, subsisting entirely on water from its food and water produced as a byproduct of metabolism.

Breeding. Breeding season of the Desert Pocket Mouse occurs in June—October. Estrus lasts a few hours, and gestation is 23-26 days. Average litter size is 3-4 young (range of 3-4). Young females can reach sexual maturity and become pregnant while still exhibitingjuvenile pelage.

Activity patterns. The Desert Pocket Mouse is nocturnal and terrestrial, and it is active throughoutthe year. Individuals readily enter periods oftorporfor several days in winter. Activity increases during mornings in late spring and early summer and decreases during the hottest part of the day. Overall activity decreases in winter, with few individuals captured in November—April. Moonlight causes individuals to forage under bushes.

Movements, Home range and Social organization. The Desert Pocket Mouse is solitary, and individuals have non-overlapping home ranges of 0-09-2-4 ha.

Status and Conservation. Classified as Least Concern on The IUCN Red List.

Bibliography. Aquino & Neiswenter (2014), Ceballos & Oliva (2005), Eisenberg & Isaac (1963), Hoffmeister & Lee (1967), Jezkova et al. (2009), Linzey, Timm, Alvarez-Castafieda, Castro-Arellano & Lacher (2008p), Mantooth & Best (2005b), Patton (1969b), Patton & Soule (1967), Price (1999c¢), Williams et al. (1993).

Figures

27. Hispid Pocket Mouse (Chaetodipus hispidus), 28. Long-tailed Pocket Mouse (Chacetodipus formosus), 29. Bailey's Pocket Mouse (Chaetodipus bailey), 30. Peninsular Pocket Mouse (Chaetodipus rudinoris), 31. Spiny Pocket Mouse (Chaetodipus spinatus), 32. California Pocket Mouse (Chaetodipus californicus), 33. San Diego Pocket Mouse (Chaetodipus fallax), 34. Little Desert Pocket Mouse (Chaetodipus arenarius), 35. Dalquest’s Pocket Mouse (Chaetodipus ammophilus), 36. Cerralvo Island Pocket Mouse (Chaetodipus siccus), 37. Desert Pocket Mouse (Chaetodipus penicillatus), 38. Chihuahuan Desert Pocket Mouse (Chaetodipus eremicus), 39. Sinaloan Pocket Mouse (Chaetodipus pernix), 40. Rock Pocket Mouse (Chaetodipus intermedius), 41. Nelson’s Pocket Mouse (Chaetodipus nelsoni), 42. Lined Pocket Mouse (Chaetodipus lineatus), 43. Goldman’s Pocket Mouse (Chaetodipus goldmani), 44. Narrow-skulled Pocket Mouse (Chaetodipus artus)

Subspecies and Distribution. C.p.penicillatusWoodhouse,1852—SWUSA(SW&SCArizona). C.p.angustirostrisOsgood,1900—SWUSAandNWMexico(SCCaliforniaandNEBajaCalifornia). C.p.priceJ.A.Allen,1894—SWUSAandNWMexico(SArizona,SWNewMexico,andSonora). C.p.seriNelson,1912—NWMexico(TiburonI,GulfofCalifornia,Sonora). C.p.sobrinusGoldman,1939—SWUSA(SENevada,SWUtah,andNWArizona). C. p. stephensi Merriam, 1894 — SW USA (EC California).