''Oligoryzomys victus'', also known as the St. Vincent colilargo or St. Vincent pygmy rice rat, 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 n ...

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 oryzomyine tribe. Only one specimen is known, which was collected on Saint Vincent in the

Lesser Antilles The Lesser Antilles ( es, link=no, Antillas Menores; french: link=no, Petites Antilles; pap, Antias Menor; nl, Kleine Antillen) are a group of islands in the Caribbean Sea. Most of them are part of a long, partially volcanic island arc bet ...

in about 1892, and it is now presumed extinct.

Taxonomy

The only known specimen was collected by H. H. Smith at an unknown location on Saint Vincent and later presented to the

British Museum of Natural History The Natural History Museum in London is a museum that exhibits a vast range of specimens from various segments of natural history. It is one of three major museums on Exhibition Road in South Kensington, the others being the Science Museum ...

, where it was registered as specimen BMNH 97.12.26.1. In 1898, Oldfield Thomas described the specimen as the

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of sever ...

of a new species of ''

Oryzomys ''Oryzomys'' is a genus of semiaquatic rodents in the tribe Oryzomyini living in southern North America and far northern South America. It includes eight species, two of which—the marsh rice rat (''O. palustris'') of the United States and ...

'' which he named ''Oryzomys victus''. Although Thomas placed it close to species now placed in ''

'', later compilators considered the affinities of ''O. victus'' as unknown; one study placed it in the ''Oryzomys tectus'' group (more or less = ''

Oecomys ''Oecomys'' is a genus of rodent within the tribe Oryzomyini of family Cricetidae. It contains about 17 species, which live in trees and are distributed across forested parts of South America, extending into Panama and Trinidad Trinidad i ...

''). In his 1962 study of Antillean oryzomyines, however, American paleontologist Clayton Ray reaffirmed its affinities with ''Oligoryzomys'', but he was unable to resolve its relation within the genus. On the one hand, he saw closer morphological similarities to small ''Oligoryzomys'' such as '' O. fulvescens'' and '' O. delicatus'', but on the other hand larger species such as '' O. longicaudatus'' are closer in size. Ray also considered the possibility that the St. Vincent population was in fact introduced from a still unknown mainland species, but considered this unlikely; no such species has since been found.

Description

The holotype, a fluid-preserved adult female with the skull extracted, was described in Thomas' original description and in Ray's 1962 restudy. It is a relatively large ''Oligoryzomys'' and has the pelage dark reddish above and buffy white below. The short ears are brown in color. The tail nearly lacks hairs and is brown above and somewhat paler below. Like most oryzomyines, it has eight

mammae A mammary gland is an exocrine gland in humans and other mammals that produces milk to feed young offspring. Mammals get their name from the Latin word ''mamma'', "breast". The mammary glands are arranged in organs such as the breasts in primat ...

, including a pectoral pair. The head and body length is 96 mm, the tail length 121 mm, the hind foot length (without claws) 25 mm, the ear length 14 mm, the greatest length of the skull 27.2 mm, the length of the upper molars is 3.9 mm, and the length of the lower molars is 4.0 mm.

Behaviour

Little is known about the habits or the ecology of ''O. victus''; in fact, the only direct information is a collector's note which calls it a "forest rat". Its morphology suggests that it was not

arboreal Arboreal locomotion is the locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally, but others are exclusively arboreal. The habitats pose nu ...

or fossorial.

Extinction

The extinction of ''O. victus'' may be associated with the introduction of the

small Asian mongoose Small Asian mongoose is a common name applied to two mammals which were formerly considered to be a single species: * Javan mongoose *Small Indian mongoose The small Indian mongoose (''Urva auropunctata'') is a mongoose species native to Iraq an ...

to St. Vincent in the 1870s. Ray suggests that the rice rat was an easier prey for the mongoose than introduced ''

Rattus ''Rattus'' is a genus of muroid rodents, all typically called rats. However, the term rat can also be applied to rodent species outside of this genus. Species and description The best-known ''Rattus'' species are the black rat (''R. rattus'') ...

'', which may have become partly arboreal, thus creating a competitive disadvantage for the rice rat. Any remaining populations may have been wiped out when the Soufrière erupted in 1902, destroying the pristine vegetation on its slopes.Ray, 1962, pp. 48–50

References

Literature cited

* *Ray, C.E. 1962. The Oryzomyine Rodents of the Antillean Subregion. Doctor of Philosophy thesis, Harvard University, 211 pp. {{Taxonbar, from=Q1761020 Oligoryzomys Extinct rodents Endemic fauna of Saint Vincent and the Grenadines Fauna of Saint Vincent and the Grenadines Taxa named by Oldfield Thomas Mammal extinctions since 1500 Taxonomy articles created by Polbot Mammals of the Caribbean