''Oligoryzomys microtis'', also known as the small-eared colilargo or small-eared pygmy rice rat, is a species of rodent in the genus ''

Oligoryzomys ''Oligoryzomys'' is a genus of rodents in the tribe Oryzomyini of family Cricetidae. Many species are known as pygmy rice rats or colilargos.Musser and Carleton, 2005 The genus is found from Mexico to Tierra del Fuego and includes approximately 1 ...

'' of family Cricetidae. It is found in western Brazil, eastern Peru,

Bolivia , image_flag = Bandera de Bolivia (Estado).svg , flag_alt = Horizontal tricolor (red, yellow, and green from top to bottom) with the coat of arms of Bolivia in the center , flag_alt2 = 7 × 7 square p ...

, and northern Paraguay.

Description

''Oligoryzomys microtis'' has a total length of including a tail of . It weighs about and is the smallest species in the genus. In proportion to the head and body length, the hind feet are relatively long, being 28.5% of their length. This compares with the rather similar ''

Oligoryzomys nigripes ''Oligoryzomys nigripes'', also known as the black-footed colilargo or the black-footed pygmy rice rat, is a rodent in the genus ''Oligoryzomys'' of family Cricetidae. Oligoryzomys nigripes is a species that has been further divided into differen ...

'' where the proportion is 24.5%. The ears are small and densely furred inside. The cheeks may be grey or orangeish-brown. The back is brownish and the underparts are whitish or greyish, sometimes tinged with buff. The tail is rather darker on the upper surface than the lower surface. Its

karyotype A karyotype is the general appearance of the complete set of metaphase chromosomes in the cells of a species or in an individual organism, mainly including their sizes, numbers, and shapes. Karyotyping is the process by which a karyotype is disce ...

has 2n = 64 and FNa = 66.

Distribution and habitat

''O. microtis'' is native to South America, its range extending from northwestern Brazil, south of the Solimões River and

Amazon River The Amazon River (, ; es, Río Amazonas, pt, Rio Amazonas) in South America is the largest river by discharge volume of water in the world, and the disputed longest river system in the world in comparison to the Nile. The headwaters of t ...

, to the adjoining lowlands of Peru and Bolivia, northern Argentina, eastern Paraguay and the Gran Chaco plain. Its typical habitat is marshes and wet grassland, but in Brazil it is more associated with forest borders, gallery woodland and secondary forest. In the Paraguayan Chaco it is associated with both dry and wet marshland, and has been reported from floating masses of vegetation.

Ecology

Breeding starts at a young age, even while still in juvenile coat, and pregnancy rates are high. In Bolivia, pregnant females have been found in March, May, August and September, and the number of embryos varied from two to eight. The

Rio Mamore virus Rio or Río is the Portuguese, Spanish, Italian, and Maltese word for "river". When spoken on its own, the word often means Rio de Janeiro, a major city in Brazil. Rio or Río may also refer to: Geography Brazil * Rio de Janeiro * Rio do Sul, a ...

has been isolated from this species in Bolivia.

Status

This is a common species over much of its wide range. It is an adaptable species, able to tolerate some habitat degradation. No particular threats have been recognised and the population seems to be stable, so the International Union for Conservation of Nature has rated its conservation status as being of least concern.

References

{{Taxonbar, from=Q1769195 Mammals of Bolivia Mammals of Brazil Mammals of Paraguay Mammals of Peru Oligoryzomys Mammals described in 1916 Taxa named by Joel Asaph Allen