Chaetodipus siccus (Osgood, 1907)

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

36.

Cerralvo Island Pocket Mouse

Chaetodipus siccus

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

Taxonomy. Perognathus penicillatus siccus Osgood, 1907 ,

“Ceralbo Island [= I Cerralvo], Lower California [= Baja California Sur], Mexico.

Based on detailed sequencing of nDNA and mtDNA genes, C. siccusis a close relative of C. arenarius and C. ammophilus , 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 siccus , formerly included as a subspecies of C. arenarius , is instead more closely related to C. ammophilus. It is morphologically indistinguishable from and allopatric to C. ammophilus and recently was considered specifically distinct from that species based on a sequence divergence of 5:5% of two mtDNA genes. Based on its morphological similarity, close distribution, and marginal mtDNA divergence from C. ammophilus, evidence from nDNA (in addition to mtDNA sequencing) is required to confirm its speciesstatus or to relegate it to a subspecies of C. ammophilus. Monotypic.

Distribution. NW Mexico (Cerralvo I and Los Planes Basin on the adjacent mainland, SE Baja California Sur).

Descriptive notes. Head—body mean 72 mm, tail mean 91 mm, hindfoot mean 22 mm, ear mean 9 mm: weight mean 14 g. Male Cerralvo Island Pocket Mice are slightly larger than females. It is 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. There are two pelage color phases, pale gray or pale buff, mixed with light and dark hairs; there is no lateral stripe; and under parts are white. Chromosomal complement has not been described. The Cerralvo Island Pocket Mouse is larger than the Little Desert Pocket Mouse ( C. arenarius ), with which it was formerly included, and closely resembles the related Dalquest’s Pocket Mouse (C. ammophilus), which surrounds its distribution in the Cape Region of the Baja California peninsula. The two are not known to occur in sympatry. In its mainland distribution in the Los Planes Basin, the Cerralvo Island Pocket Mouse occurs in the vicinity of the Spiny Pocket Mouse ( C. spinatus ), which inhabits rocky soils and is not found on sandy soils to which the Cerralvo Island Pocket Mouse is restricted. The Spiny Pocket Mouse has darker pelage that is course in appearance, with numerous stiff spines, particularly on rump.

Habitat. Restricted to sandy soils and sparsely vegetated regions of Cerralvo Island and adjacent Los Planes Basin of the Baja California Peninsula. On Cerralvo Island, the Cerralvo Island Pocket Mouse is most common on the flat, sandy south-western part of the island and less common on slopes and ridges. It is found far up sandy arroyos with a sandy floor, suggesting that sandy soil is a more important aspect of the habitat than is a flat, open environment.

Food and Feeding. Diet of the Cerralvo Island 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. Two embryos were found in a female Cerralvo Island Pocket Mouse in March.

Activity patterns. The Cerralvo Island 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. The Cerralvo Island Pocket Mouse has not been assessed on The IUCN Red List.

Bibliography. Alvarez-Castafeda & Rios (2011), Aquino & Neiswenter (2014), 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)

Distribution. NW Mexico (Cerralvo I and Los Planes Basin on the adjacent mainland, SE Baja California Sur).