Chaetodipus pernix (J. A. Allen, 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 : 217

39.

Sinaloan Pocket Mouse

Chaetodipus pernix

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

Taxonomy. Perognathus pernix J. A. Allen, 1898 ,

Rosario, Sinaloa, Mexico.

Based on detailed sequencing of nDNA and mtDNA genes, C. pernixis a close relative of the sister-taxon pair of C. penicillatus and C. eremicus , and all three 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 . Mitochondrial sequence analysis confirmed that the three karyotypic forms of C. pernix form a monophyletic clade sister to the clade including C. penicillatus and C. eremicus . Two subspecies recognized.

Subspecies and Distribution.

C.p.pernix].A.Allen,1898—NWMexico(C&SSinaloaandNNayarit).

C. p. rostratus Osgood, 1900 — NW Mexico (S Sonora and N Sinaloa).

Descriptive notes. Head—body mean 75 mm, tail mean 83 mm, hindfoot mean 21 mm, ear mean 10 mm, weight mean 17 g. Male Sinaloan Pocket Mice are slightly larger than females. The northern subspecies rostratus is about the same size as the Desert Pocket Mouse ( C. penicillatus ) and larger than the southern subspecies ( pernix ). The Sinaloan Pocket Mouse is smooth-haired and small-sized for the genus, with tail longer than head-body length, thinly haired with small crest, and small ears. Relatively soft pelage is usually lacking spines on rump, and if present, these are rather inconspicuous, small, and not asstiff compared with those of coarse-haired species. Pelage of the Sinaloan Pocket Mice is yellowish brown, mixed with light and dark hairs; there is a broad fulvous lateral stripe, under parts are white, and post-auricular patch is only slightly lighter than dorsum. Chromosomal complement either has 2n = 52 and FN = 56 (rostratus) or 2n = 36, FN = 56 ( pernix from Playas Novillero, on a barrier island in north-western Nayarit on the southern edge ofits distribution) or 2n = 38, FN = 56 ( pernix from Pericos, Sinaloa, near the northern edge ofits distribution). The Sinaloan Pocket Mouse occurs in a narrow zone of sympatry in southern Sonora with the Desert Pocket Mouse ( C. penicillatus ). Hybridization without introgression between these two species was reported at one locality in agriculturally disturbed habitat. Hybrids had 2n = 49, intermediate between that of the two species, and female hybrids had significantly fewer placental scars, suggesting that hybrids were partially or completely sterile. Compared with the Desert Pocket Mouse,tail of the Sinaloan Pocket Mouse is thinly haired with small crest. In its distribution in the southern Sonoran Desert, the Sinaloan Pocket Mouse is sometimes captured on the same trap lines as three other species of coarse-haired pocket mice. Bailey’s Pocket Mouse ( C. baileyi ) is larger (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.” Goldman's Pocket Mouse ( C. goldmani ) and the Narrow-skulled Pocket Mouse ( C. artus ) have conspicuous rump spines and occur on gravelly or rocky soils but not in sandy soils to which the Sinaloan Pocket Mouseis restricted.

Habitat. Habitats with thorny leguminous trees, arborescent cacti, a dense understory of cacti ( Opuntia , Cactaceae ), and small woody shrubs on fine alluvial silt nearly devoid of rocks. The Sinaloan Pocket Mouse is restricted to sandy soils in arid coastal plains of Sinaloan thornscrub from the Presa Alvaro Obregon in southern Sonora to Novillero in north-western Nayarit, from barrier islands (including Playas Novillero, Nayarit and Hacienda Island, Sinaloa) at sea level to the lower end of valleys draining the Sierra Madre Occidental at elevations below 90 m. The Sinaloan Pocket Mouse is common on plains below the oak ( Quercus , Fagaceae ) belt, along river bottoms and along edges of cultivated fields. In sand dunes along the Gulf of California near Las Glorias, Sinaloa, in January 2005, 240 live traps yielded only two species of mammals: 57 specimens of the Sinaloan Pocket Mouse and seven specimens of the Southern Grasshopper Mouse (Onychomys torridus), a rodent that preys upon other small rodents and invertebrates.

Food and Feeding. Diet of the Sinaloan Pocket Mouse consists largely of seeds of shrubs, annuals, and grasses, butit 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. Young Sinaloan Pocket Mice are born in October-November in the north, and two females in Sinaloa had one and three embryos in early April. There are usually c.7 placentalscars.

Activity patterns. The Sinaloan 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. Preferred habitat of the Sinaloan Pocket Mouse is actively undergoing agricultural conversion and fragmentation in the Sinaloan coastal plains.

Bibliography. Alvarez-Castafieda, Castro-Arellano & Lacher (2008e), Aquino & Neiswenter (2014), Best (1993a), Best & Lackey (1992b), Ceballos & Oliva (2005), Patton & Soule (1967), 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.p.pernix].A.Allen,1898—NWMexico(C&SSinaloaandNNayarit). C. p. rostratus Osgood, 1900 — NW Mexico (S Sonora and N Sinaloa).