332.

Burmeister’s Cotton Rat

Sigmodon hirsutus

French: Sigmodon hirsute / German: Burmeister-Baumwollratte / Spanish: Rata de algodon de Burmeister

Other common names: Southern Cotton Rat

Taxonomy. Lasiomys hirsutus Burmeister, 1855, Maracaibo, Zulia, Venezuela.

Sigmodon hirsutus was long considered a subspecies or synonym of S. Aispidus until molecular analyses documented strong genetic divergence and cladistic separation. Assignment of bogotensis, borucae, chiriquensis, and griseus was confirmed by molecular analyses and that of bogotensis and sanctamartae, by morphological comparisons; current assignment of austerulus needs confirmation. The Middle American populations have received no revisionary attention and thus merit close scrutiny to delimit diagnosably defensible infraspecific units; South American populations have been reviewed and are regarded as monotypic. Monotypic.

Distribution. SE Mexico (E Oaxaca and Chiapas) S through Middle America (excluding N Guatemala, Belize, and NW Honduras) to the Caribbean lowlands of Colombia S through Magdalena Valley and E to N Venezuela.

Descriptive notes. Head-body 125-227 mm, tail 92-165 mm, ear 19-23 mm, hindfoot 34-37 mm. No specific data are available for body weight. Burmeister’s Cotton Rat is large-bodied, with brown or grayish and strongly grizzled dorsal pelage and whitish to pale orange belly. It is molecularly distinct from the Hispid Cotton Rat (S. luspidus) and the Toltec Cotton Rat (S. toltecus), but it has not been adequately compared with either species to enable a useful delineation of diagnosable morphological attributes, as has been done with other South American species such as the Groovetoothed Cotton Rat (S. alstoni), the Ecuadorean Cotton Rat (S. inopinatus), and the Peruvian Cotton Rat (S. peruanus). Chromosomal complement is 2n = 52, FNa = 52.

Habitat. Natural or anthropogenic non-forested habitats usually dominated by grass, near streams,irrigation ditches, and other moist areas, within savannas, pastures, croplands, and grassy openingsin forest, mostly at elevations of 500-1500 m. The speciesis very tolerant of deforested areas that have accompanied human settlements; no specimens have been collected from undisturbed rainforest in South America.

Food and Feeding. In Los Llanos of Venezuela, diet of Burmeister’s Cotton Rat consisted primarily of the green parts of grasses and herbaceous dicotyledonous plants.

Breeding. In Los Llanos of Venezuela, breeding of Burmeister’s Cotton Rat is continuous throughout annual cycles of flooding and drought, but it is most intense in rainy season when densities reach their peaks.

Activity patterns. Burmeister’s Cotton Ratis active day and night.

Movements, Home range and Social organization. Maximum densities have been estimated at 51 ind/ha in autumn, with minimum of 25 ind/ha in summer.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Burmeister’s Cotton Rat has a wide distribution and presumably large overall population; it occurs in several protected areas and lacks known conservation threats.

Bibliography. Allen (1897a, 1897d, 1904, 1908), Bangs (1898a, 1902), Bradley et al. (2008), Burmeister (1855), Carroll et al. (2005), Ceballos (2014a), Delgado et al. (2016), Lessmann et al. (2011), Monge (2008), Musser & Carleton (2005), Reid (2009), Ruiz (1984), Vivas & Calero (1988), Voss (1992, 2015f).