Chaetodipus eremicus (Mearns, 1898)

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 : 216-217

38.

Chihuahuan Desert Pocket Mouse

Chaetodipus eremicus

French: Souris-a-abajoues du Chihuahua / German: Chihuahua-Rauhaartaschenmaus / Spanish: Raton de abazones de Chihuahua

Other common names: Chihuahuan Pocket Mouse, Eastern Desert Pocket Mouse

Taxonomy. Perognathus (Chaetodipus) eremicus Mearns, 1898 ,

Fort Hancock, El Paso [now in Hudspeth] Co., Texas, USA.

Based on detailed sequencing of nDNA and mtDNA genes, C. eremicus is a close relative of C. penicillatus , with which it was formerly considered to be conspecific. These 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 . Two subspecies recognized.

Subspecies and Distribution.

C.e.eremicusMearns,1898—SWUSAandNMexico(SNewMexico,SWTexas,Chi-huahuatoNWSanLuisPotosi).

C. e. atrodorsalis Dalquest, 1951 — NE Mexico (S Nuevo Leon, SW Tamaulipas, and N San Luis Potosi).

Descriptive notes. Head—body 70-81 mm, tail 77-98 mm, ear 7-9 mm, hindfoot 21- 25 mm; weight 13-19 g. There is no significant secondary sexual dimorphism. The Chihuahuan Desert Pocket Mouse is a smooth-haired pocket mouse and 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 notasstiff compared with those of the coarse-haired species. Pelage is pale pinkish buff, buffy brown, or near fuscous 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 = 56. The Chihuahuan Desert Pocket Mouse closely resembles its close relative, the Desert Pocket Mouse ( C. penicillatus ), with which it is parapatric or narrowly sympatric in south-western New Mexico. The Chihuahuan Desert Pocket Mouse has shortertail but is larger in most external and cranial measurements, has a lighter, more mottled pelage color with a less sharply defined lateral line, and has a more prominent postauricular patch. In its distribution in the Chihuahuan Desert, the Chihuahuan Desert Pocket Mouse is sometimes captured in the general vicinity (same trap lines) as the Hispid Pocket Mouse (C. hispidus ), and either of two coarse-haired species, the Rock Pocket Mouse (C. intermedius ) or Nelson’s Pocket Mouse ( C. nelsoni ). Both coarsehaired species have conspicuous spines on rump and occur in rocky and gravelly soils, not in sandy soils to which the Chihuahuan Desert Pocket Mouse is restricted. The Hispid Pocket Mouse is associated with desert grassland and has a short, non-crested, and non-tufted tail and coarse pelage that is olive buff with a distinctive ocherous lateral stripe. In south-western New Mexico, the Chihuahuan Desert Pocket Mouse is sometimes captured along with Bailey's Pocket Mouse ( C. baileyi ), which is considerably larger (e.g. hindfoot length longer than 25 mm) and more often occurs on pebbly soils that mark transitions from sandy flats to rocky alluvial slopes or “bajadas.”

Habitat. Restricted to sandy soils throughout the Chihuahuan Desert, at elevations below ¢.1700 m in desert grassland with creosote bush ( Larrea divaricata, Zygophyllaceae ), prickly pear ( Opuntia rastrera, Cactaceae ), catclaw ( Acacia , Fabaceae ), and mesquite ( Prosopis , Fabaceae ). Elongated or fan-shaped burrows of Chihuahuan Desert Pocket Mice are located near bases of bushes and shrubs and are plugged with sand during the daytime. Underground, several openings and tunnels radiate from a central burrow cavity or nest. One study demonstrated that the Chihuahuan Desert Pocket Mouse actively excludes a sympatric coarse-haired species, the Rock Pocket Mouse, from burrow habitats in sandy soils that provide a microhabitat in which the sand-obligate species can survive and that the Rock Pocket Mouse has a broader tolerance for more extreme environments.

Food and Feeding. Diet of the Chihuahuan Desert Pocket Mouse consists largely of seeds of shrubs, annuals, and grasses, but it also includes smaller amounts of green vegetation and insects. Seeds eaten include broomweed ( Gutierrezia , Asteraceae ), creosote bush, mesquite, and grasses. Food items are collected in external, fur-lined cheek pouches and transported back to burrows, where they are stored in burrow caches. The Chihuahuan Desert Pocket Mouse does not need to drink water, subsisting entirely on water from its food and water produced as a byproduct of metabolism.

Breeding. Breeding season in the Chihuahuan Desert Pocket Mouse occurs in February—August, with a major peak in April and smaller peaks in June and August. Females have 3-4 embryos/litter. Young females can reach sexual maturity and become pregnant while still exhibitingjuvenile pelage.

Activity patterns. The Chihuahuan Desert Pocket Mouse is nocturnal and terrestrial, and it is active throughout the year. Individuals may enter periods of torpor for several days during winter.

Movements, Home range and Social organization. There is no information available for this species.

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

Bibliography. Aquino & Neiswenter (2014), Ceballos & Oliva (2005), Hoffmeister & Lee (1967), Lee et al. (1996), Linzey, Timm, Alvarez-Castafieda, Castro-Arellano & Lacher (2008j), Mantooth & Best (2005a), 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.e.eremicusMearns,1898—SWUSAandNMexico(SNewMexico,SWTexas,Chi-huahuatoNWSanLuisPotosi). C. e. atrodorsalis Dalquest, 1951 — NE Mexico (S Nuevo Leon, SW Tamaulipas, and N San Luis Potosi).