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Tawny-bellied Cotton Rat

Sigmodon fulviventer

French: Sigmodon a ventre roux / German: Gelbbraune Baumwollratte / Spanish: Rata de algodén de vientre leonado

Taxonomy. Sigmodon fulviventer]. A. Allen, 1889, Zacatecas, Zacatecas, Mexico.

Subspecies minimus includes woodi named by A. L. Gardner in 1948, as a junior synonym. Five subspecies currently recognized.

Subspecies and Distribution.

S.f.fulviventer].A.Allen,1889—CDurangoSthroughtheCMexicanPlateautoNEJaliscoandTlaxcala,Mexico.

S.f.dalquestiStangl,1992—anisolatedtaxonknownonlyfromitstypelocalityinSWTexas.

S.f.goldmaniBailey,1913—knownonlyfromthetypelocalityinSWNewMexico,butpresumedtobeextinct.

S.f.melanotisBailey,1902—EJaliscoandWMichoacan,Mexico.

S. f. minimus Mearns, 1894 — SE Arizona and SW New Mexico, USA, S through E Sonora and Chihuahua to N Durango, Mexico.

Descriptive notes. Head-body 138-200 mm, tail 101-118 mm, ear 19-23 mm, hindfoot 26-31 mm; weight 82-136 g. The Tawny-bellied Cotton Rat is medium-sized, with conspicuous tawny brown-orange underparts and saltand-pepper grizzled dorsum that varies from brown, black, or black with brown tipped hairs. Tail is dark and only sparsely covered by hair. Tail, feet, and ears are moderately long. Tawny belly, mottled color of back, and moderate size distinguishes the Tawny-bellied Cotton Rat from other species of Sigmodon . Distinctive craniodental features include narrow anterior tip of mesopterygoid fossa, long foramen ovale equal in width to M?, deeply marked palatal fossa, and welldeveloped median keel on palatine. Chromosomal complementis 2n = 28-30, FNa = 34.

Habitat. Mesquite-grasslands and other grass-shrub communities in the Chihuahuan Desert at elevations of 1290-2475 m.

Food and Feeding. The Tawny-bellied Cotton Rat is primarily herbivorous and can consume up to 0-27 kg of grass/ha/ day .

Breeding. Sexual maturity of captive Tawny-bellied Cotton Rats was reached by 70-77 days of age, gestation was c.35 days, and litters had 4-6 young.

Activity patterns. Tawny-bellied Cotton Rats arestrictly terrestrial and might be active day and night.

Movements, Home range and Social organization. Tawny-bellied Cotton Rats travel along well-defined paths, usually in dense grasses. Burrows are built in dense vegetation, at bases of fallen trees or their stumps, and belowground; aboveground wovengrass nests are found in dense and tall grass. Densities can reach 28 ind/ha, with local population numbers varying considerably among years. Among syntopic congeners, the Tawny-bellied Cotton Rat is dominant, actively excluding other species.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Tawnybellied Cotton Rat is widely distributed, presumably has a large overall population size, and does not appear to face any conservation threats. It is occurs in protected areas. Nevertheless, subspecies goldmani —a peripheral isolate in New Mexico—is now considered extinct.

Bibliography. Allen (1889), Alvarez-Castafieda, Castro-Arellano & Lacher (2016b), Bailey (1902, 1913), Baker (1969), Baker & Shump (1978a), Ceballos (2014a), Elder & Lee (1985), Findley & Jones (1963), Gardner (1948a), Harris & Petersen (1979), Hoffmeister (1986), Jiménez (1971, 1972), Lee & Zimmerman (1969), Mearns (1894), Petersen (1973, 1979), Petersen & Helland (1978), Ramirez & Chavez (2014c), Stangl (1992), Swier et al. (2009), Zimmerman (1970).