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Ecuadorean Cotton Rat

Sigmodon inopinatus

French: Sigmodon andin / German: EkuadorBaumwollratte / Spanish: Rata de algodén de Ecuador

Other common names: Unexpected Cotton Rat

Taxonomy. Sigmodon inopinatus Anthony, 1924, “Urbina, slopes of [Volcan] Chimborazo [Provincia Chimborazo], Ecuador; altitude 11,400 feet [= 3475 m].” This species is monotypic.

Distribution. Known only from the high Andes in SC Ecuador.

Descriptive notes. Head-body 136-167 mm, tail 78-99 mm, ear 14-22 mm, hindfoot 28-30 mm. No specific data are available for body weight. The Ecuadorean Cotton Rat is relatively large-bodied, with proportionally short tail (55-58% of head-body length) and hindfeet (c.19% of head-body length). It has relatively long dorsal fur (14-15 mm); back is gray-brown-clay, grizzled with black and sprinkling of white-tipped hairs; belly is gray-brown, with basal dark tones showing through; tail is brown dorsally and whitish below; hands and feet are grizzled gray; and clay-colored orbital ring is well defined. Cranially, the Ecuadorean Cotton Rat can be distinguished from other species of South American Sigmodon by its short nasal bones (exposing incisors in dorsal view); very narrow interorbital region; long incisive foramina (usually extending between molar alveoli); unconstricted palatal bridge; posterior palatal foramina usually bordered by maxillary and palatine bones; small auditory bullae; procumbent, but still weakly opisthodont, ungrooved upper incisors; upper molars with opposite, obtusely rounded cusps; and first mandibular molars usually with four well-developed roots. Karyotype is unknown.

Habitat. Treeless paramo vegetation among tufts of bunch grasses and mossy hummocks, other grassy places including those with mixtures of grass and shrubby aster family plants, and in or near marshy areas at elevations of 3500-3800 m.

Food and Feeding. The Ecuadorean Cotton Rat is presumably primarily herbivorous.

Breeding. One female Ecuadorean Cotton Rat had four embryos.

Activity patterns. The Ecuadorean Cotton Ratis terrestrial and presumably diurnal and nocturnal.

Movements, Home range and Social organization. No information.

Status and Conservation. Classified as Vulnerable on The IUCN Red List. The Ecuadorean Cotton Rat has a very restricted distribution, and its population has no doubt declined due to accelerated deforestation, habitat conversion to agriculture, and fragmentation. It is found in Cajas National Park.

Bibliography. Anthony (1924a), Barnett (1999), Tirira (2007), Tirira & Boada (2008), Tirira & Vallejo-Vargas (2015), Voss (1992, 2015f).