''Oligoryzomys stramineus'', also known as the straw-colored colilargo or straw-colored pygmy rice rat,Duff and Lawson, 2004 is a species of

rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are na ...

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 the family

Cricetidae The Cricetidae are a family of rodents in the large and complex superfamily Muroidea. It includes true hamsters, voles, lemmings, muskrats, and New World rats and mice. At almost 608 species, it is the second-largest family of mammals, and has m ...

. It occurs only in the

cerrado The ''Cerrado'' (, ) is a vast ecoregion of tropical savanna in eastern Brazil, particularly in the states of Goiás, Mato Grosso do Sul, Mato Grosso, Tocantins, Minas Gerais, and the Federal District. The core areas of the Cerrado biome are t ...

and

caatinga Caatinga (, ) is a type of semi-arid tropical vegetation, and an ecoregion characterized by this vegetation in interior northeastern Brazil. The name "Caatinga" is a Tupi word meaning "white forest" or "white vegetation" (''caa'' = forest, v ...

ecoregions of northeastern

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

. 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 = 52 and FNa = 68-70.

Description

''Oligoryzomys stramineus'' is a large species of colilargo with a yellowish-brown head and dorsal surface and whitish underparts, with a sharp line demarcating the boundary between the two. It has long

incisive foramina In the human mouth, the incisive foramen (also known as: "''anterior palatine foramen''", or "''nasopalatine foramen''") is the opening of the incisive canals on the hard palate immediately behind the incisor teeth. It gives passage to blood vesse ...

(openings in the hard palate of the skull) and broad

zygomatic plate In rodent anatomy, the zygomatic plate is a bony plate derived from the flattened front part of the zygomatic arch (cheekbone). At the back, it connects to the front (maxillary) root of the zygomatic arch, and at the top it is connected to the ...

s (bony plates in the upper jaw). The head-and-body length averages while the tail averages .

Distribution and habitat

This species is native to South America where it occurs in northeastern and central Brazil. Its range extends from the

ecoregion of the states of northern

Goiás Goiás () is a Brazilian state located in the Center-West region. Goiás borders the Federal District and the states of (from north clockwise) Tocantins, Bahia, Minas Gerais, Mato Grosso do Sul and Mato Grosso. The state capital is Goiânia. ...

and northern

Minas Gerais Minas Gerais () is a state in Southeastern Brazil. It ranks as the second most populous, the third by gross domestic product (GDP), and the fourth largest by area in the country. The state's capital and largest city, Belo Horizonte (literally ...

southward to the

ecoregion of the states of

Paraíba Paraíba ( Tupi: ''pa'ra a'íba''; ) is a state of Brazil. It is located in the Brazilian Northeast, and it is bordered by Rio Grande do Norte to the north, Ceará to the west, Pernambuco to the south and the Atlantic Ocean to the east. Paraíba ...

and

Pernambuco Pernambuco () is a state of Brazil, located in the Northeast region of the country. With an estimated population of 9.6 million people as of 2020, making it seventh-most populous state of Brazil and with around 98,148 km², being the 19 ...

. In the cerrado, it has mainly been found in

gallery forest A gallery forest is one formed as a corridor along rivers or wetlands, projecting into landscapes that are otherwise only sparsely treed such as savannas, grasslands, or deserts. The gallery forest maintains a more temperate microclimate above th ...

s. It shares part of its range in central Brazil with '' Oligoryzomys fornesi'' and is sometimes caught in the same line of traps. It is also

sympatric In biology, two related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter one another. An initially interbreeding population that splits into two or more distinct species sh ...

with ''

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 ...

'', but the two species are not found in the same trap-lines.

Ecology

Little is known of the breeding habits of ''O. stramineus''; a pregnant female carrying four young was caught in September; and a juvenile was caught in August suggesting that mating may have occurred in June or July.

Status

''O. stramineus'' has a wide range, and though its total population is not known, it is considered to be common and its population stable. No particular threats have been identified and the

International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

has rated its conservation status as being of "

least concern A least-concern species is a species that has been categorized by the International Union for Conservation of Nature (IUCN) as evaluated as not being a focus of species conservation because the specific species is still plentiful in the wild. T ...

References

Literature cited

*Duff, A. and Lawson, A. 2004. Mammals of the World: A checklist. New Haven: A & C Black. . * *Weksler, M. and Bonvicino, C. 2008. . In IUCN. IUCN Red List of Threatened Species. Version 2009.2.
www.iucnredlist.org
. Downloaded on September 5, 2015. {{Taxonbar, from=Q1765642 Oligoryzomys Mammals described in 1998 Fauna of the Cerrado Taxa named by Marcelo Weksler