Chaetodipus ammophilus, 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 : 215

35.

Dalquest’s Pocket Mouse

Chaetodipus ammophilus

French: Souris-a-ajaboues de Dalquest / German: Dalquest-Rauhaartaschenmaus / Spanish: Raton de abazones de Dalquest

Taxonomy. Perognathus penicillatus ammophilus Osgood, 1907 ,

Santa Margarita Island, Baja California Sur, Mexico

In 2011, S.. T Alvarez-Castaneda and E. Rios reassigned two subspecies from C. arenarius (ammophilus and sublucidus) to C. dalquesti . In 2013, E. Rios and S. T. Alvarez-Castaneda synonymized C. dalquesti to C. ammophilus recognizing taxonomic priority of the latter. Based on detailed sequencing of nDNA and mtDNA genes,

C. ammophilus is a close relative of C. arenarius and C. siccus , and all three are part of the Baja California Peninsula lineage of the “modern” clade of Chaetodipus pocket mice, along with C. fallax , C. californicus , and C. spinatus . Chaetodipus ammophilus is generally parapatric with the closely related C. arenarius , in which it was previously included. Three subspecies recognized.

Subspecies and Distribution.

C.a.ammophilusOsgood,1907—NWMexico(restrictedtoSantaMargaritaI,SWBaja C.a. Sur).

. C.a.dalquestiRoth,1976—NWMexico(SPacificcoastandC.a.RegionofBajaC.forniaSur).

C. a. sublucidus Nelson & Goldman, 1929 — NW Mexico (coast S & E of the Bahia de la Paz, except the El Magote sand spit, S Baja C.a. Sur).

Descriptive notes. Head-body mean 72 mm, tail mean 91 mm, ear mean 9 mm, hindfoot mean 22 mm; weight mean 14 g. Male Dalquest’s Pocket Mice are slightly larger than females. Thisis a smooth-haired pocket mouse and small-sized for the genus, with tail longer than head-body length and small ears. Relatively soft pelage has only a few spines on rump, and 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 lateral stripe; and under parts are white. Chromosomal complement has 2n = 42 and FN = 64. Dalquest’s Pocket Mouse is generally parapatric with the closely related Little Desert Pocket Mouse ( C. arenarius ), but the two species have been found in sympatry at three localities within 75 km of Ciudad Insurgentes on the Magdalena Plains and near La Paz, Baja California Sur. Where captured together in the same trap line in 1999 and 2005 (25 km N Insurgentes, 25°29’52-8"N, 111°51°14-4"N), specimens of Dalquest’s Pocket Mouse were somewhat larger in external measurements (mean and ranges): head-body 73-9 mm (67-80 mm) vs. 70-1 mm (66-72 mm); tail 86-6 mm (84-96 mm) vs. 80-8 mm (78-84 mm); hindfoot 21-4 mm (20-22 mm) vs. 19-8 mm (18-21 mm); ear 9 mm (9 mm) vs. 7-5 mm (7-9 mm); weight 12:4 g (11-14 g) vs. 10 g (9-11 g). Dalquest’s Pocket Mouse averages larger in most cranial measurements, which are similar to those of the parapatric Cerralvo Island Pocket Mouse ( C. siccus ) of Cerralvo Island and the mainland Los Planes Basin. No areas of sympatry between the latter two species are known, but the two are more closely related to each other than to the Little Desert Pocket Mouse. Where populations of the Spiny Pocket Mouse ( C. spinatus ) occur in the general vicinity, the latter inhabits rocky soils and is not found on sandy soils to which Dalquest’s Pocket Mouse is restricted. The Spiny Pocket Mouse has a darker pelage that is course in appearance, with numerousstiff spines, particularly on rump.

Habitat. Sandy soils in the Cape Region of Baja California Sur from Santa Margarita Island on the Pacific coast to La Paz and south at elevations below 600 m. Dalquest’s Pocket Mouse is restricted to moist, cool areas of coastal plains in desert scrubland that is subject to coastal fog and contains epiphytes, primarily the lichen-like fungi Roccella and ball moss ( Tillandsia recurvata, Bromeliaceae ). Its habitat along the Pacific coast contains many endemic plant species. Dalquest’s Pocket Mouse occurs in three general and discontinuous areas on Santa Margarita Island, along the Pacific coast, and around La Paz. The low-elevation, narrow isthmus between the Pacific coast and La Paz allows cool, moist breezes from the Pacific Ocean during at least part of the year.

Food and Feeding. Diet of Dalquest’s 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. Breeding season of Dalquest’s Pocket Mouse occurs in April-August.

Activity patterns. Dalquest’s 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 Vulnerable on The IUCN Red List (as C. dalquesti ). Extensive agricultural development on the Magdalena Plainsis rapidly destroying habitat of Dalquest’s Pocket Mouse.

Bibliography. Alvarez-Castafeda & Rios (2011), Alvarez-Castaneda, Castro-Arellano & Lacher (2008d), Aquino & Neiswenter (2014), Ceballos & Oliva (2005), Rios & Alvarez-Castaneda (2010, 2013), 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.ammophilusOsgood,1907—NWMexico(restrictedtoSantaMargaritaI,SWBaja C.a. Sur). . C.a.dalquestiRoth,1976—NWMexico(SPacificcoastandC.a.RegionofBajaC.forniaSur). C. a. sublucidus Nelson & Goldman, 1929 — NW Mexico (coast S & E of the Bahia de la Paz, except the El Magote sand spit, S Baja C.a. Sur).