Chaetodipus arenarius (Merriam, 1894)

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 : 214-215

34.

Little Desert Pocket Mouse

Chaetodipus arenarius

French: Souris-a-abajoues des sables / German: Kleine Rauhaartaschenmaus / Spanish: Raton de abazones pequefo de desierto

Other common names: Sand Pocket Mouse

Taxonomy. Perognathus arenarius Merriam, 1894 ,

near Comondu, San Jorge, Baja California Sur, Mexico.

Based on detailed sequencing of nDNA and mtDNA genes, C. arenarius is a close relative of C. ammophilus and C. siccus , and all three are part of the Baja California Peninsula lineage of the “modern” clade of coarse-haired pocket mice, along with C. fallax , C. californicus , and C. spinatus . Nine subspecies recognized.

Subspecies and Distribution.

C.a.arenariusMerriam,1894—NWMexico(fromnearLagunaSanIgnacioStoWofBahiadelaPaz,BajaC.a.Sur).

C.a.albescensHuey,1926—NWMexico(GulfcoastinvicinityofSanFelipe,BajaC.a.forniaSur).

C.a.albulusNelson&Goldman,1923—NWMexico(MagdalenaI,BajaC.a.Sur).

C.a.ambiguusNelson&Goldman,1929—NWMexico(ValledelosCirios,SBajaC.a.fornia,andVizcainoDesert,NBajaC.a.Sur).

C.a.helleriElliot,1903—NWMexico(SanQuintinPlain,NWBajaC.a.).

C.a.mexicalisHuey,1939—NWMexico(WsideofLagunaSalada,NEBajaC.a.).

C.a.paraliosHuey,1964—NWMexico(GulfcoastofSEBajaC.a.).

C.a.ramirezpulidoiAlvarez-Castanieda&Cortés-Calva,2004—NWMexico(ElMagotesandspit,BahiadelaPaz,BajaC.a.Sur).

C. a. sabulosus Huey, 1964 — NW Mexico (Bahia de Santa Rosaliita, Baja C.a., S through the W Vizcaino Desertto the vicinity of the Laguna San Ignacio, Baja C.a. nia Sur).

Descriptive notes. Head-body mean 70 mm (males) and 67 mm (females), tail mean 86 mm (males) and 85 mm (females), ear mean 8 mm, hindfoot mean 21 mm; weight mean 11 g. Male Little Desert Pocket Mice are slightly larger than females. It is a smoothhaired pocket mouse and small-sized for the genus, with 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 pale gray or pale buff, mixed with light and dark hairs; there is no lateralstripe except buffy lateral stripe in Aelleri and darkly colored populations of other subspecies; under parts are white. Chromosomal complement has 2n = 42 and FN = 64. The Little Desert Pocket Mouse is generally parapatric with closely related Dalquest’s Pocket Mouse (C. ammophilus), which was formerly included with this species. The Little Desert Pocket Mouse closely resembles the Desert Pocket Mouse ( C. penicillatus ), with which it is parapatric or narrowly sympatric in north-eastern Baja California . In this region, the Little Desert Pocket Mouse averages smaller, interorbital breadth is more than 25-8% of occipitonasal length (vs. less than 25%), and dorsal pelage is uniform smoke gray (vs. yellowish-brown). In its distribution on the Baja California peninsula, the Little Desert Pocket Mouse is sometimes captured on same trap lines as the Peninsular Pocket Mouse ( C. rudinoris ), the San Diego Pocket Mouse ( C. fallax ), or the Spiny Pocket Mouse ( C. spinatus ). Where populations of the Spiny Pocket Mouse occur in the general vicinity, it inhabits rocky soils and is not found on sandy soils to which the Little Desert Pocket Mouse is restricted. The Spiny Pocket Mouse has a darker pelage that is course in appearance, with numerousstiff spines, particularly on rump. The San Diego Pocket Mouse, a coarse-haired species,is larger and more colorful, with a dark-brown back and yellowish to orangish hairs on its sides and numerous rump bristles. It occurs in sandy to rocky soils in sparse to dense coastal sage vegetation. The Peninsular Pocket Mouse, while lacking rump spines,is much larger and is usually associated with pebbly soils that mark transitions from sandy flats to rocky alluvial slopes or “bajadas.”

Habitat. Sandy soils in arid (often extremely arid) and sparsely vegetated regions throughout the Baja California peninsula, at elevations below 600 m. The Little Desert Pocket Mouse is at most narrowly sympatric with other sand-obligate species of the genus that occupy the north-eastern and southern regions of the peninsula. At twelve sites at which the Little Desert Pocket Mouse was trapped,it co-occurred with the Peninsular Pocket Mouse at eleven sites, with the Spiny Pocket Mouse at seven sites, and with the San Diego Pocket Mouse at one site.

Food and Feeding. Diet of the Little Desert Pocket Mouse consists largely of seeds of shrubs, annuals, and grasses, but it also includes smaller amounts of green vegetation and insects. 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. A female Little Desert Pocket Mouse with two embryos was reported in March, and two females with two placental scars each were found in May.

Activity patterns. The Little Desert Pocket Mouse is nocturnal and terrestrial, and it is active throughout the year.

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 List. A recently described subspecies of the Little Desert Pocket Mouse, ramirezpulidoi, is restricted to a sandy coastal barrier bar (El Mogote, 1540 ha) that divides the lagoon of La Paz from La Paz Bay. The sand spit has been subjected to development, and plans include only 52 ha to remain under natural conditions, although even these will be subjected to non-native species (domestic cats, Felis catus, dogs, and house mice, Mus).

Bibliography. Alvarez-Castaneda & Cortés-Calva (2004), Alvarez-Castaneda & Rios (2011), Alvarez-Castafeda, Castro-Arellano & Lacher (2008b), Aquino & Neiswenter (2014), Best (1993a), Ceballos & Oliva (2005), Lackey (1991a), 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.a.arenariusMerriam,1894—NWMexico(fromnearLagunaSanIgnacioStoWofBahiadelaPaz,BajaC.a.Sur). C.a.albescensHuey,1926—NWMexico(GulfcoastinvicinityofSanFelipe,BajaC.a.forniaSur). C.a.albulusNelson&Goldman,1923—NWMexico(MagdalenaI,BajaC.a.Sur). C.a.ambiguusNelson&Goldman,1929—NWMexico(ValledelosCirios,SBajaC.a.fornia,andVizcainoDesert,NBajaC.a.Sur). C.a.helleriElliot,1903—NWMexico(SanQuintinPlain,NWBajaC.a.). C.a.mexicalisHuey,1939—NWMexico(WsideofLagunaSalada,NEBajaC.a.). C.a.paraliosHuey,1964—NWMexico(GulfcoastofSEBajaC.a.). C.a.ramirezpulidoiAlvarez-Castanieda&Cortés-Calva,2004—NWMexico(ElMagotesandspit,BahiadelaPaz,BajaC.a.Sur). C. a. sabulosus Huey, 1964 — NW Mexico (Bahia de Santa Rosaliita, Baja C.a., S through the W Vizcaino Desertto the vicinity of the Laguna San Ignacio, Baja C.a. nia Sur).