422.

Azara’s Rice Rat

Hylaeamys megacephalus

French: Oryzomys de d’Azara / German: Azara-Reisratte / Spanish: Rata arrocera de Azara

Other common names: Azara’s Broad-headed Oryzomys, Azara’s Hylaeamys

Taxonomy. Mus megacephalus G. Fischer, 1814, type not locality given. Fixed by neotype selection by G. G. Musser and colleagues in 1998 as “Departamento de Canendiyu [= Canindeyu], 13- 3 km N Curuguaty (24°31’S / 55°42’W) in east-central Paraguay east of the Rio Paraguay.”

Important molecular and morphological variation is included in the current concept of H. megacephalus . Its complicated taxonomic history includes several nominal forms such as Oryzomys velutinus and O. goeldi. Monotypic.

Distribution. E & S Venezuela, Trinidad I, the Guianas, N, C & SE Brazil, and E Paraguay.

Descriptive notes. Head-body 80-158 mm, tail 90-138 mm, ear 19 mm, hindfoot 28 mm; weight 42 g. Azara’s Rice Rat is medium-sized, with dorsal fur short, dense, slightly harsh, and overall ocherous, yellowish, or orangish, weakly to moderately ticked with dark brown; ventral is fur shorter and predominantly gray, often with small white gular and inguinal patches;tail is unicolored or weakly to completely bicolored; ears are sparsely covered with either entirely brown or banded hairs, brown basally but white or golden distally. Hindfeet are short, with small plantar pads (especially hypothenar), and sparse ungual tufts are shorter than claws. Chromosomal complement is 2n = 54, FN = 62.

Habitat. Forested areas of the Cerrado and Chaco including semideciduous forests, Amazonian forests, and forested areas in the Venezuelan Llanos at elevations of 15— 1100 m. Azara’s Rice Rats live in well-drained, swampy, or creekside primary and secondary forests, and they can be common near human dwellings and rock outcrops and in overgrown orchards.

Food and Feeding. Azara’s Rice Rat eats mainly fruits and seeds.

Breeding. Pregnant Azara’s Rice Rats and reproductively active males have been observed in dry and wet seasons in Cerrado ecoregion. In French Guiana, births and pregnant females are noted year-round, with peaks coincident with rainy season. Gestation of captive individuals is 26 days, and litters have 1-6 young. Pregnant females were caught in December (dry season) in transition between Llanos and Amazonian forest in Brazil.

Activity patterns. Azara’s Rice Rat is nocturnal and predominantly terrestrial, but it can be scansorial, with arboreal captures always in lower forest strata. Individuals in French Guiana were caught on the ground (64%, n = 36) and in lianas 0-3-1-2 m aboveground (19%).

Movements, Home range and Social organization. In the gallery forests of Cerrado, density of Azara’s Rice Rat increased in the dry season, reaching 7-5 ind/ha. In central Brazilian Amazonia, density was at 0-4 ind/ha.

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

Bibliography. Costa (2003), Malcolm (1988, 1991), Mares & Ernest (1995), Mares et al. (1986), Musser & Carleton (2005), Musser, Carleton et al. (1998), Nitikman & Mares (1987), Ochoa et al. (1988), Patton, da Silva & Malcom (2000), Pena (2016), Percequillo, Patton et al. (2016), Voss et al. (2001), Weksler et al. (2006).