Chaetodipus rudinoris (Elliot, 1903)

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 : 212-213

30.

Peninsular Pocket Mouse

Chaetodipus rudinoris

French: Souris-a-abajoues de San Quintin / German: Halbinsel-Rauhaartaschenmaus / Spanish: Raton de abazones de Baja California

Other common names: Baja California Pocket Mouse, Baja Pocket Mouse

Taxonomy. Perognathus baileyi rudinoris Elliot, 1903 ,

San Quintin, Baja California, Mexico.

Based on detailed sequencing of nDNA and mtDNA genes, C. rudinorisis a close relative of C. baileyi , with which it was formerly considered conspecific. These two species together make up one of the three “ancient” clades of coarse-haired pocket mice. Chaetodipus rudinoris has a chromosomal complement with a higher FN = 66, lacks any supernumerary chromosomes, and is differentiated based on allozymes and mitochondrial sequence. Five subspecies recognized, following E. R. Hall's synonymizing the subspecies knekus under rudinorisin 1981 without comment and subsequent publications by D. D. Paulson, D. F. Williams and colleagues, and B. R. Riddle and colleagues.

Subspecies and Distribution.

C.r.rudinorisElliot,1903—NWMexico(CBajaCalifornia).

C.r.extimusNelson&Goldman,1930—NWMexico(SWBajaCaliforniaSur).

C.r.fornicatusBurt,1932—NWMexico(MonserratI,GulfofCalifornia,BajaCaliforniaSur);butmaybeextinct.

C.r.huey:Nelson&Goldman,1929—SWUSAandNWMexicoWoftheColoradoRiver(SECaliforniaandNEBajaCalifornia).

C. r. mesidios Huey, 1964 — NW Mexico (C & S Baja California , including Coronado, Pata, and Mitlan Is in Gulf of California , N & C Baja California Sur ).

Descriptive notes. Head-body 85-99 mm, tail 103-124 mm, ear 7-11 mm, hindfoot 25— 27 mm; weight 24-28 g. Male Peninsular Pocket Mice are slightly larger than females. It is large-sized for the genus; hindfoot is usually longer than 25 mm, with strongly crested and tufted tail that is longer than head-body length. Dorsal pelage is relatively smooth, lacks spines on rump, and is grayish, washed to varying degrees with yellow; under parts are whitish. Chromosomal complement has 2n = 46 and FN = 66. The Peninsular Pocket Mouse is parapatric with its close relative Bailey's Pocket Mouse (C. baileyt) on the opposite side of the Colorado River. Bailey's Pocket Mouse on the east side of the Colorado River has darker pelage and wider rostrum than the Peninsular Pocket Mouse on the west side ofthe river. In 2006, the Peninsular Pocket Mouse was captured at 40 km northnorth-east of San Roque in Baja California Sur , extending its known distribution to the west side of the Vizcaino Desert. The Peninsular Pocket Mouse co-occurs with six other species of coarse-haired pocket mice. In addition to being larger than the other species (hindfoot usually longer than 25 mm), the Peninsular Pocket Mouse favors more open areas of pebbly soils that mark transitions from sandy flats to rocky alluvial slopes or “bajadas,” apart from the sand-obligate, smooth-haired species in the same vicinity (the Desert Pocket Mouse, C. penicillatus , and the Little Desert Pocket Mouse, C. arenarius ) and apart from the saxicolous (rock-dwelling) species in the vicinity (the Long-tailed Pocket Mouse, C. formosus ; the Spiny Pocket Mouse, C. spinatus ; the San Diego Pocket Mouse, C. fallax ; and the California Pocket Mouse, C. californicus ).

Habitat. Areas with medium to large bushes and trees, often in ecotonal areas between rocky hillsides and desert flats. The Peninsular Pocket Mouse also ranges into low desert flats, small sandy washes, and rocky hillsides. It occurs most frequently with the Little Desert Pocket Mouse ( C. arenarius ), sometimes using areas with coarser, more gravelly soils. In some areas, the Peninsular Pocket Mouse is associated with jojoba (Stmmondsia chinensis, Simmondsiaceae ), and the combined distribution of the Peninsular Pocket Mouse and its close relative, Bailey’s Pocket Mouse, closely matches distribution of the jojoba. Burrows of the Peninsular Pocket Mouse are often found at bases ofjojoba bushes. The Peninsular Pocket Mouse does occur in absence ofjojoba.

Food and Feeding. Diet of the Peninsular Pocket Mouse consists largely of seeds of shrubs, annuals, and grasses, but it also includes smaller amounts of green vegetation and insects. In laboratory experiments, it selected larger seeds than other heteromyids tested. Like Bailey’s Pocket Mouse, the Peninsular Pocket Mouse apparently has some detoxification abilities that allowsit to eat seeds ofjojoba that have toxic cyanogenic glucosides and are rejected by the Desert Pocket Mouse, the Rock Pocket Mouse (C. intermedius ), and Merriam’s Kangaroo Rat ( Dipodomys merriami ) in laboratory tests. Other common foods of the Peninsular Pocket Mouse include seeds of cholla ( Opuntia , Cactaceae ) and ocotillo ( Fouquieria , Fouquieriaceae ); grass seeds are less frequently taken.

Food items are collected in external, fur-lined cheek pouches and transported back to burrows, where they are stored in burrow caches. Volume of cheek pouches (1-6 cm?) is sufficient to carry daily energy requirements of an individual in a single seed load. The Peninsular Pocket Mouse does not need to drink water, subsisting entirely on water from its food and water produced as a byproduct of metabolism.

Breeding. There is no information available for this species.

Activity patterns. The Peninsular Pocket Mouse is nocturnal and terrestrial.

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. The population on Monserrat Island (fornicatus) may be extinct, apparently due to predation by feral cats (Felis catus). Populations on the three islands near Bahia Los Angeles (Smith, Pata, and Mitlan) are stable.

Bibliography. Aquino & Neiswenter (2014), Ceballos & Oliva (2005), Hall (1981), Linzey, Timm, Alvarez-Castaneda, Castro-Arellano & Lacher (2008q), Paulson (1988a), Price (1999b), Riddle, Hafner & Alexander (2000), Stapp & Polis (2003), 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.r.rudinorisElliot,1903—NWMexico(CBajaCalifornia). C.r.extimusNelson&Goldman,1930—NWMexico(SWBajaCaliforniaSur). C.r.fornicatusBurt,1932—NWMexico(MonserratI,GulfofCalifornia,BajaCaliforniaSur);butmaybeextinct. C.r.huey:Nelson&Goldman,1929—SWUSAandNWMexicoWoftheColoradoRiver(SECaliforniaandNEBajaCalifornia). C. r. mesidios Huey, 1964 — NW Mexico (C & S Baja California , including Coronado, Pata, and Mitlan Is in Gulf of California , N & C Baja California Sur ).