Chaetodipus fallax (Merriam, 1889)

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

33.

San Diego Pocket Mouse

Chaetodipus fallax

French: Souris-a-abajoues de San Diego / German: Kurzohr-Rauhaartaschenmaus / Spanish: Raton de abazones de San Diego

Other common names: Short-eared Pocket Mouse; Anthony's Pocket Mouse (anthony)

Taxonomy. Perognathus fallax Merriam, 1889 ,

“San Bernardino, Cal.,” USA.

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

Subspecies and Distribution.

C. f. fallaxMerriam, 1889 — SWUSAandNWMexico (PacificcoastsideofSanBernardinoMts, SWCaliforniaStoSierraJuarez, NBajaCalifornia).

C.f.anthonyiOsgood,1900—NWMexico(CedrosI,BajaCalifornia ).

C. f. inopinusNelson & Goldman, 1929 — NWMexico (PacificcoastofSBajaCalifornia)

.

C.f.majusculusHuey,1960—NWMexico(PacificcoastofCBajaCalifornia ).

C.f.pallidusMearns,1901—SWUSA(SMojaveDeserttoCalifornia—BajaCalifornia border).

C. f. xerotrophicus Huey, 1960 — NW Mexico (C Baja California).

Descriptive notes. Head-body 82-87 mm, tail 88-118 mm, ear mean 10 mm, hindfoot mean 24 mm; weight 17-22 g. There is no significant secondary sexual dimorphism. The San Diego Pocket Mouse is medium-sized to large-sized for the genus, with bicolored, crested, tufted tail that is longer than head-body length. Dark dorsal stripe on tail is narrower than light ventralstripe. Dorsal pelage is harsh, dark brown, with conspicuous black spines on rump and white spines on hip, buffy lateral stripe, and whitish under parts. Chromosomal complement has 2n = 44 and FN = 56. The San Diego Pocket Mouse is elevationally parapatric with its close relative, the California Pocket Mouse ( C. californicus ), which occupies denser chaparral above more arid habitats of the San Diego Pocket Mouse. The California Pocket Mouse is larger, with longer ears and relatively longertail. The San Diego Pocket Mouse also is found with or near six other coarse-haired pocket mice: the Long-tailed Pocket Mouse (C. formosus ), which is somewhat smaller and lacks rump spines; the Peninsular Pocket Mouse ( C. rudinoris ), which is larger and lacks rump spines; the Spiny Pocket Mouse ( C. spinatus ), which is blackish-gray and with more spines; and the Little Desert Pocket Mouse ( C. arenarius ) and Desert Pocket Mouse ( C. penicillatus ), which are smaller, lighter in color, lack rump spines, and restricted to sandy soils.

Habitat. Desert and coastal habitats of sparse, low desert shrublands to dense coastal sage scrub, usually on rocky soils, from sea level to elevations of ¢.1400 m. Burrow systems of San Diego Pocket Mice are usually near bushes and can be quite elaborate, with nesting and seed-storage chambers and multiple entrances.

Food and Feeding. Diet of the San Diego 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, furlined 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 of the San Diego Pocket Mouse takes place primarily in spring, and 1-3 litters of 2-6 young each may be produced each year.

Activity patterns. The San Diego Pocket Mouse is nocturnal and terrestrial, and it is active throughout the year. Individuals may become torpid for 1-2 months when food is scarce.

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.

Bibliography. Aquino & Neiswenter (2014), Ceballos & Oliva (2005), Linzey, Timm, Alvarez-Castaneda, Castro-Arellano & Lacher (2008k), Lackey (1996), Longland (1999), Rios & Alvarez-Castafeda (2010, 2013), Williams etal. (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. f. fallaxMerriam, 1889 — SWUSAandNWMexico (PacificcoastsideofSanBernardinoMts, SWCaliforniaStoSierraJuarez, NBajaCalifornia). C.f.anthonyiOsgood,1900—NWMexico(CedrosI,BajaCalifornia ). C. f. inopinusNelson & Goldman, 1929 — NWMexico (PacificcoastofSBajaCalifornia) . C.f.majusculusHuey,1960—NWMexico(PacificcoastofCBajaCalifornia ). C.f.pallidusMearns,1901—SWUSA(SMojaveDeserttoCalifornia—BajaCalifornia border). C. f. xerotrophicus Huey, 1960 — NW Mexico (C Baja California).