446.

Yellow Pygmy Rice Rat

Oligoryzomys flavescens

French: Colilargo doré / German: Gelbe Zwergreisratte / Spanish: Rata arrocera pigmea dorada

Other common names: Flavescent Colilargo

Taxonomy. Mus flavescens Waterhouse, 1837, “Maldonado,” Maldonado, UruBUY.

Genetic data suggests that O. flavescens may be a composite of at least two, if not three, species. At least two forms, both with type localities in Argentina, occidentalis and antoniae, are available for binomial or trinomial classifications. Monotypic.

Distribution. E & S Brazil, extreme SC Bolivia (Tarija Department), Paraguay, N & C Argentina, and Uruguay.

Descriptive notes. Head—body 81-93 mm, tail 97-130 mm, ear 15-16 mm, hindfoot 22-24 mm; weight 15-21 g. The Yellow Pygmy Rice Rat is a small species, characterized by bright brownish orange dorsum, finely intermixed with dark hair; sides are brighter orange. Skull has long incisive foramina that usually reach M' and short mesopterygoid fossa that does not reach M*.

Habitat. Pampas, Chaco, Atlantic Forest (pristine and second-growth communities), and gallery forests in Cerrado near limits with Atlantic Forest. The Yellow Pygmy Rice Rat is also found along cropland borders in Argentina, Uruguay, and southern Brazil. It was captured at sites with low dry shrub cover and high green grass cover. In Argentina, it is rarely trapped in forests, replaced there by the Black-footed Pygmy Rice Rat ( O. nigripes) or the Chacoan Pygmy Rice Rat ( O. chacoensis).

Food and Feeding. The Yellow Pygmy Rice Rat is omnivorous, with proportions of food items varying seasonally.

Breeding. Reproduction of the Yellow Pygmy Rice Rat occurs from spring to autumn. Litters have 3-7 young (average five).

Activity patterns. The Yellow Pygmy Rice Rat is nocturnal and manily terrestrial; strong ability to climb has been reported.

Movements, Home range and Social organization. In a study in central Argentina, the Yellow Pygmy Rice Rat was the only species (of four) that did not overlap or cross paths with conspecifics or individuals from other species. Population explosions have been reported in relation to flowering of bamboo ( Merostachys skvortzovii, Poaceae) in Brazil, but little demographic change was associated with harvesting or plowing. Nevertheless, social organization appears to change after harvesting because most adult males disappeared, presumably due to increased emigration or mortality.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Yellow Pygmy Rice Rat has a broad distribution and presumably large and stable populations.

Bibliography. Bilenca et al. (1995), Bonaventura et al. (2003), Busch & Kravetz (1992, 1993), Busch et al. (1997), Calderén et al. (1999), Canepuccia et al. (2008), Cantoni et al. (2001), Carballido et al. (2011), Cavia et al. (2009), Cittadino et al. (1997), Coda et al. (2015), Contreras & Rosi (1980), Courtalon & Busch (2010), Crespo (1966), Ellis, Mills, Childs et al. (1997), Ellis, Mills, Glass et al. (1998), Ellis, Mills, Kennedy et al. (1994), Fernandez et al. (2012), Fornes & Massoia (1965), Gomez et al. (2012), Gonzalez et al. (2012), Jayat, Ortiz & Miotti (2008), Kufner et al. (2004), Langguth (1963), Lareschi (1996), Maroli et al. (2015), Massoia (1983), Mills, Alva et al. (2007), Mills, Barrera et al. (1996), Mills, Ellis, McKee, Ksiazek et al. (1991), Mills, Ellis, McKee, Maiztegui & Childs (1991, 1992), Mills, Schmidt et al. (2007), Mino, Cavia, Gémez, Bilenca & Busch (2007), Mino, Cavia, Gobmez, Bilenca, Cittadino & Busch (2001), Palma et al. (2012), Polop (1989), Reig (1965), Rosario et al. (2015), Vadell & Gomez (2016), Vadell et al. (2011), de Villafane, Bonaventura et al. (1988), de Villafane, Merler et al. (1992), Weksler & Bonvicino (2015b), Weksler, Bonvicino, D’Elia et al. (2016).