386.

White-bellied Arboreal Rice Rat

Oecomys bicolor

French: Oecomys bicolore / German: \WeilRbauch-Baumreisratte / Spanish: Rata arrocera arboricola de vientre blanco

Other common names: Bicolored Arboreal Rice Rat, White-bellied Oecomys

Taxonomy. Hesperomys bicolor Tomes, 1860, “Gualaquiza,” Morona Santiago, Ecuador .

Morphological, karyologycal, and molecular variability in the distribution of O. bicolor suggests occurrence of diagnosable geographical races or a species complex; taxonomic review is needed. Monotypic.

Distribution. E Panama, Colombia, Venezuela, the Guianas, N & C Brazil, NW Ecuador, Peru, and Amazon Basin of Bolivia.

Descriptive notes. Head-body 94-107 mm, tail 99-119 mm, ear 13-15 mm, hindfoot 21-23 mm; weight 25-37 g. Oecomys encompasses small to medium-sized oryzomyines, with soft fur, tails typically longer than head-body length with apical tuft or pencil, and short and broad hindfeet with relatively long toes and poorly developed claws. General body plan seems to be associated to arboreal activities. Dorsum varies from grayish brown to tawny and reddish brown, and venter varies from pure white to dark gray. There are four pairs of mammae. Pelage of the White-bellied Arboreal Rice Rat is dense, felt-like, and relatively short (3-6 mm on rump). Dorsal pelage ranges from rich ocherous tawny (nearly orange brown) to rufous brown, finely mixed with dark brown over mid-dorsum and becoming slightly paler along lower sides of head and body, a bright buffy gray. Ventral pelage is bright and uniformly white in most specimens, although it can also include hairs with white bases and buff to ocherous tips. Tail is unicolored and 105-112% of head-body length, with moderate terminal pencil, notably long hairs extend 5-7 mm beyond tip, and typically 20 scale rows/cm. Cranially, zygomatic notches are very shallow, more so than in other species of Oecomys; well-developed and strongly diverging supraorbital ledges extend as ridges onto parietals; upper incisors are slightly opisthodont; bullae are small and uninflated; and carotid circulatory plan is complete. Chromosomal complements are 2n = 80, FN = 142 in populations from Jatapu and Purus rivers (Brazil); 2n = 82, FN = 116 in populations from Jari River (Brazil); 2n = 80, FN = 140 in population from Jurua River (Brazil); and 2n = 80, FN = 134 or 136 in populations from Curanja and Purus rivers (Peru)

Habitat. Tropical primary and secondary evergreen forests, seasonally inundated forests (varzea), upland forest (terra firma), and commensal settings, such as orchards, overgrown fields, and rustic dwellings, from sea level to elevations up to 1537 m.

Food and Feeding. Diet of the White-bellied Arboreal Rice Rat contains arthropods and plant parts.

Breeding. White-bellied Arboreal Rice Rats breed year-round. Most males might not be reproductive active at any given time, but many females can be pregnant or lactating. Pregnant females have been recorded throughout the dry season and beginning of the rainy season (August-February). Averagelitter size is 2-1 (range 2-3). The White-bellied Arboreal Rice Rat becomes sexually mature at ¢.3 months.

Activity patterns. White-bellied Arboreal Rice Rats are nocturnal, terrestrial, and arboreal. They have been caught in canopies (74%) and on the ground (26%). They use trees such as Dendropanax umbellatus ( Araliaceae), Tetrastylidium peruvianum ( Olacaceae), Iryanthera tessmannii ( Myristicaceae), Theobroma obovatum ( Malvaceae), and Helicostylis tometosa ( Moraceae).

Movements, Home range and Social organization. No information.

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

Bibliography. Carleton & Musser (2015), Eisenberg & Redford (1999), Emmons et al. (2006), Gardner & Patton (1976), Gomes et al. (2016), Handley (1976), Hershkovitz (1960), Hice & Velazco (2012), Hutterer et al. (1995), Linares (1998), Lira (2012), Musser & Carleton (1993, 2005), Patton et al. (2000), Pino et al. (2016), Rosa et al. (2012), Voss et al. (2001).