Chaetodipus nelsoni (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 : 218

41.

Nelson’s Pocket Mouse

Chaetodipus nelsoni

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

Taxonomy. Perognathus (Chaetodipus) nelsont Merriam, 1894 ,

“Hacienda La Parada, San Luis Potosi, Mexico.”

Based on detailed sequencing of nDNA and mtDNA genes, C. nelsoni is related to the sister-taxon pair of C. goldmani and C. artus , and all three are part of the continental lineage of the “modern” clade of coarse-haired pocket mice, along with another coarse-haired species (C. intermedius ) and three smooth-haired species (C. penicillatus, C. eremicus , and C. pernix ). Populations within the south-eastern distribution of C. nelsoni in central San Luis Potosi and extreme north-eastern Zacatecas have been described as a separate species, C. lineatus , which is supposedly sympatric throughout its distribution with C. nelsoni , including several specific locations. Nowhere else in the entire distribution of the genus are two species of either smooth-haired or coarse-haired pocket mice of the modern lineage of this genus widely sympatric. Two subspecies recognized.

Subspecies and Distribution.

C.n.nelsoniMerriam,1894—NCMexico(SMexicanPlateaufromSCChihuahuatoNJalisco).

C. n. canescens Merriam, 1894 — SW USA and N Mexico (W Texas and N Mexican Plateau to S Coahuila and NE Durango, and a disjunct population in SE New Mexico).

Descriptive notes. Head-body 78-81 mm, tail 88-115 mm, hindfoot mean 21 mm, ear mean 8 mm, weight 14-18 g. There is no significant secondary sexual dimorphism.

Nelson’s Pocket Mouse is coarse-haired and medium-sized for the genus, with tail that is longer than head-body length, sparsely haired on basal one-half; terminal one-half is crested, penicillate, and indistinctly bicolored. Pelageis relatively coarse with numerous conspicuous black-tipped spines on rump. Pelage is brown, with a well-defined lateralstripe that is fawn in color and white under parts. Soles of hindfeet are black. A disjunct population of Nelson's Pocket Mouse occurs in the Guadalupe Mountains of south-eastern New Mexico, along a small part of the eastern escarpment within Carlsbad Caverns National Park. This rare mouse was first captured in 1952 and 1953, rediscovered in 1991, and sampled genetically in 2003. It is closely related to the northern clade (north of the Rio Grande in Texas) of the subspecies canescens. As in the Beach Mountains of Texas, this population appears to be surrounded by low-elevation populations of another saxicolous pocket mouse, the Rock Pocket Mouse (C. intermedius ).

Nelson’s Pocket Mouse has a nearly complementary distribution in the Chihuahuan Desert with the Rock Pocket Mouse. The two are narrowly sympatric in western Texas, and both have been collected at two localities just east of the Rio Grande.It is likely that the two species, which are not sister-taxa, competitively exclude each other along a front of contact, as their habitat requirements appear to be very similar. Nelson's Pocket Mouse is larger, has more rump spines, and has black soles on the hindfeet.

Throughoutits range in the Chihuahuan Desert south of the Rio Conchos, Nelson's Pocket Mouse is commonly captured in the generalvicinity of two other pocket mice, neither of which occurs in the rocky habitat of this species. The Hispid Pocket Mouse (C. luspidus) 1s larger, with a short, non-crested or penicillate tail, is more colorful and lacks rump spines, and prefers sandy soil and desert grassland. The Chihuahuan Desert Pocket Mouse lacks rump spines and is restricted to sandy soils.

Habitat. Rocky soils and rocky slopes but also sandy soils where rock walls or old stone buildings provide a substitute rocky habitat or in heavily disturbed sites. Nelson's Pocket Mouse clearly prefers rocky slopes with cactus ( Opuntia , Cactaceae ), creosote bush ( Larrea , Zygophyllaceae ), sotol ( Dasylirion , Asparagaceae ), and lechugilla ( Agave , Asparagaceae ). It is a widespread and common species throughout the Chihuahuan Desert, south of the Rio Conchos. Its small burrows are dug at the bases of desert shrubs, particularly thorny bushes.

Food and Feeding. Diet of Nelson'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 Nelson's Pocket Mouse is 5-8 months, beginning in February with a peak in March. Average litter size is three young (range 1-5), and gestation is ¢.30 days. Young females of the year are able to breed later in the same season.

Activity patterns. Nelson’s Pocket Mouse is nocturnal and terrestrial, and it is active throughout the year. It rarely strays from shelter of bushes or rocks while foraging.

Movements, Home range and Social organization. Home ranges of male Nelson's Pocket Mice (0-31 ha) are larger than those of females (0-26 ha), and there is a tendency for home ranges of males to overlap during period of higher density and higher reproductive activity. Estimates of densities fluctuate widely from season to season: low of 1-8 ind/ha to 60-9 ind/ha in late spring and early summer when ¢c.65% of the population may be young-of-the-year.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The population of Nelson’s Pocket Mouse in the Guadalupe Mountains of New Mexico, although rare and geographically isolated and restricted, is protected within Carlsbad Caverns National Park.

Bibliography. Aquino & Neiswenter (2014), Best (1993a, 1994a), Ceballos & Oliva (2005), Geluso & Geluso (2004, 2015), Linzey, Timm, Alvarez-Castafieda, Castro-Arellano & Lacher (20080), Schmidly (1999), Wilkins & Schmidly (1979), 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.n.nelsoniMerriam,1894—NCMexico(SMexicanPlateaufromSCChihuahuatoNJalisco). C. n. canescens Merriam, 1894 — SW USA and N Mexico (W Texas and N Mexican Plateau to S Coahuila and NE Durango, and a disjunct population in SE New Mexico).