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Groove-toothed Cotton Rat

Sigmodon alstoni

French: Sigmodon d’Alston / German: Furchenzahn-Baumwoliratte / Spanish: Rata de algodén de dientes estriados

Other common names: Alston's Cotton Rat

Taxonomy. Reithrodon alstoni Thomas, 1881, Cumana, Sucre, Venezuela.

Sugmodon alstoni originally was placed in Reithrodon and subsequently as the type species of Sigmomys, now regarded a synonym of Sigmodon . Monotypic.

Distribution. NE Colombia, Venezuela, the Guianas, and NE Brazil.

Descriptive notes. Head-body 106-152 mm, tail 72-102 mm, ear 30 mm, hindfoot 30-36 mm; weight 74 g. The Groove-toothed Cotton Rat is small-bodied, with proportionately long tail and hindfeet. Dorsum is agouti-brown, and venter is gray. Eyes are ringed with pale yellow hairs. Cranially, the Groove-toothed Cotton Rat can be distinguished from all other congeners by its by broad, strongly opisthodont, and deeply grooved upper incisors. It can also be distinguished from other South American species of Sigmodon by long nasal bones; unconstricted interorbital region; incisive foramina that usually extend to or between molar alveoli; posterior palatal foramina that always border maxillary and palatine bones; derived stapedial circulation pattern; small auditory bullae; upper molars with opposite, obtusely rounded cusps; and first mandibular molars with only three well-developed roots. Diploid numbers vary from 2n = 78 to 82.

Habitat. Open, grassy habitats such as savannas, pastures, overgrown gardens, and weedy roadsides at elevations below ¢.1300 m.

Food and Feeding. The Groove-toothed Cotton Rat is predominantly herbivorous, with strong preference for grass in feeding trials. It can be a major crop pest, consuming large quantities of grain.

Breeding. The Groove-toothed Cotton Rat breeds year-round, even in habitats with seasonal flooding and drought. Litters average five young. Local populations fluctuate depending on rainfall and food abundance.

Activity patterns. The Groove-toothed Cotton Rat is strictly terrestrial, and is both diurnal and noctural.

Movements, Home range and Social organization. Groove-toothed Cotton Rats construct runways through low vegetation.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Groove-toothed Cotton Rat has a wide distribution and presumably large overall population. It occurs in protected areas and does not face any major conservation threats.

Bibliography. Handley (1976), Ibanez & Moreno (1982), Martino & Aguilera (1993), O'Connell (1981, 1982), Patton, Weksler, Delgado et al. (2016), Reig (1986), Thomas (1881, 1901b, 1914b), Vivas (1986), Voss (1992, 2015f).