377.

Merida Rice Rat

Nephelomys meridensis

French: Néphélomys de Mérida / German: Merida-Reisratte / Spanish: Rata arrocera de Mérida

Other common names: Merida Nephelomys, Merida Oryzomys

Taxonomy. Oryzomys meridensis Thomas, 1894, “ Merida, Venezuela.”

Nephelomys meridensis was originally described in 1894 as a species of Oryzomys and considered close to O. albigularis (currently Nephelomys albigularis) and O. wvelutinus (currently included in Hylaeamys megacephalus). In the next two decades, various other species were described in the groups with O. albigularis and O. meridensis, which were eventually consolidated under O. albigularis by P. Hershkovitz in 1944. Because of differences in karyotype and morphology, O. meridensis was reinstated as a species separate from O. albigularis and the other Venezuelan member of the group, O. caracolus . When species of the O. albigularis group were reclassified into the new genus Nephelomys in 2006, it was retained as a species, now N. meridensis . Populations in Tachira have a different karyotype and might represent a different species, and morphological and karyological differences have been highlighted for populations in Paramo de Tama. Monotypic.

Distribution. E Andes Range of NE Colombia and W Venezuela.

Descriptive notes. Head—body 135-160 mm, tail 170-172 mm, ear 17-22 mm, hindfoot 23-36 mm; weight 50-74 g. The Merida Rice Rat is medium-sized, with tail typically unicolored but rarely weakly bicolored; dorsal pelage is dense, lax, and very long; and ventral pelage has large pectoral patches of single-colored hair (gular, axillary, and inguinal patches are rarely present). Chromosomal complement is 2n = 66, FN = 104.

Habitat. Forested slopes at elevations of 1100-4000 m. Merida Rice Rats were caught in ground litter and under logs and roots in dense, cold forested areas.

Food and Feeding. The Merida Rice Rat is omnivorous, with a tendency to eat seeds and fruits.

Breeding. Merida Rice Rats reproduce year-round, and females were pregnant, lactating, or in estrous for several months. Postpartum estrus was observed in captivity and the wild. Estrous cycle in captivity can last more than five days because some phases were extended by more than two days. No relationship was found between frequency of reproductive females in each reproductive state and monthly average of rainfall or variation in food availability (e.g. arthropod abundance and oak fruiting).

Activity patterns. Merida Rice Rats are nocturnal and terrestrial.

Movements, Home range and Social organization. Merida Rice Rats are solitary.

Status and Conservation. Classified as Least Concern on The IUCN Red List.

Bibliography. Aguilera et al. (1995), Anderson & Raza (2010), Cardenas (2017), Goldman (1918a), Handley (1976), Hershkovitz (1944), Marquez et al. (2000), Osgood (1912), Percequillo (2015g, 2016), Rivas (1993, 1997), Rivas & Péfaur (1999), Thomas (1894), Villamizar-Ramirez et al. (2017), Weksler et al. (2006).