''Abrothrix olivacea'', also known as the olive grass mouse or olive akodont,Musser and Carleton, 2005, p. 1090 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 ''

Abrothrix ''Abrothrix'' is a genus of rodent in the tribe Abrotrichini of family Cricetidae. It contains the following living species:Teta et al., 2017 *''Abrothrix andina'' *''Abrothrix hershkovitzi'' *''Abrothrix hirta'' *''Abrothrix illutea'' *''Abrothri ...

'' of 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 is found from northern

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...

into southern Chile and

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

, including the islands of

Tierra del Fuego Tierra del Fuego (, ; Spanish for "Land of the Fire", rarely also Fireland in English) is an archipelago off the southernmost tip of the South American mainland, across the Strait of Magellan. The archipelago consists of the main island, Isla G ...

. It is prone to large swings in population size.

Taxonomy

''Abrothrix olivacea'' has had a complex history in both of the genera ''

Akodon ''Akodon'' is a genus consisting of South American grass mice. They mostly occur south of the Amazon Basin and along the Andes north to Venezuela, but are absent from much of the basin itself, the far south of the continent, and the lowlands west ...

'' and ''Abrothrix'', and includes at least 27

synonyms A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...

. A few, including ''markhami'', ''mansoensis'', and ''xanthorhinus'' have been viewed as valid species until recent years, and several

subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...

are still recognized, including ''Abrothrix olivacea markhami''.

Description

The olive grass mouse is a small rodent with a total length of about . The upper parts are greyish-brown, sometimes slightly yellowish around the snout, and the underparts are pale to mid-grey.

Distribution and habitat

This species is found in northern and central Chile and the westernmost fringes of Argentina, southern Chile and Patagonia, including the larger offshore islands and the islands of

. Its habitat varies; in Patagonia it inhabits arid bushy steppes; further north it is found in the forests of ''

Nothofagus ''Nothofagus'', also known as the southern beeches, is a genus of 43 species of trees and shrubs native to the Southern Hemisphere in southern South America (Chile, Argentina) and Australasia (east and southeast Australia, New Zealand, New Gui ...

'', ''

Saxegothaea ''Saxegothaea'' is a genus comprising a single species, ''Saxegothaea conspicua''. It is a conifer in the podocarp family Podocarpaceae, native to southern South America. It grows in Chile and Argentina from 35° to 46° South latitude; in its nor ...

'' and

bamboo Bamboos are a diverse group of evergreen perennial flowering plants making up the subfamily Bambusoideae of the grass family Poaceae. Giant bamboos are the largest members of the grass family. The origin of the word "bamboo" is uncertain, bu ...

; elsewhere it occurs in tussocky grassland, marshes and wet meadows.

Ecology

The olive grass mouse is mostly diurnal. In grassy habitats, it creates runways and makes a nest of grasses in a tussock, among roots or under a rock. It can climb and also dig, and in Chile it sometimes occupies burrows made by other mammals such as the

coruro The coruro (''Spalacopus cyanus'') is a species of rodent in the family Octodontidae. It is the only species in the genus ''Spalacopus''. The species is endemic to central Chile, where it has been found in a wide variety of habitats, from coast ...

(''Spalacopus cyanus''). It feeds on berries, seeds, shoots, leaves, fungi and small invertebrates. It breeds in spring and summer and litter sizes average five young. Under favourable conditions, and in

El Niño El Niño (; ; ) is the warm phase of the El Niño–Southern Oscillation (ENSO) and is associated with a band of warm ocean water that develops in the central and east-central equatorial Pacific (approximately between the International Date L ...

years, populations can increase dramatically. This mouse is preyed on by

barn owl The barn owl (''Tyto alba'') is the most widely distributed species of owl in the world and one of the most widespread of all species of birds, being found almost everywhere except for the polar and desert regions, Asia north of the Himalaya ...

s (''Tyto tyto'') and

lesser horned owl The lesser horned owl or Magellanic horned owl (''Bubo magellanicus'') is a large owl of the genus ''Bubo'' found in southern South America, extending north to the central Andes. It has traditionally been classified as a subspecies of the great h ...

s (''Bubo magellanicus''), various other birds and foxes. The Olive grass mouse is a host of the

Acanthocephalan Acanthocephala (Greek , ', thorn + , ', head) is a phylum of parasitic worms known as acanthocephalans, thorny-headed worms, or spiny-headed worms, characterized by the presence of an eversible proboscis, armed with spines, which it uses to p ...

intestinal parasite ''

Moniliformis amini Moniliformidae is a family of parasitic spiny-headed (or thorny-headed) worms. It is the only family in the Moniliformida order and contains three genera: ''Australiformis'' containing a single species, ''Moniliformis'' containing eighteen specie ...

''. Outbreaks of this species sometimes occur. In 1990, the bamboo ''

Chusquea valdiviensis ''Chusquea'' is a genus of evergreen bamboos in the grass family. Most of them are native to mountain habitats in Latin America, from Mexico to southern Chile and Argentina. They are sometimes referred to as South American mountain bamboos. Unli ...

'' had a mass seeding phenomenon in which over a million hectares of this bamboo in southern Chile flowered at the same time and then died. The enormous quantities of seeds were followed by a mass population increase of the rice rat ''

Oligoryzomys longicaudatus ''Oligoryzomys longicaudatus'', also known as the long-tailed colilargo or long-tailed pygmy rice rat, is a species of rodent in the genus '' Oligoryzomys'' of the family Cricetidae. It is found in the southern Andes of Chile and Argentina, with ...

'' and to a lesser extent, of the olive grass mouse. Increases in rodent numbers can be attributed to a greater fecundity, a higher survival rate of juveniles and an extension in the breeding season. Since many of the bamboo seeds were retained within the flowering spikelets for a year, further rodent population peaks occurred in subsequent years.

Status

''A. olivacea'' is a common species with a presumed large population. It has a wide range and is present in several protected areas. It seems tolerant of habitat degradation and no particular threats have been identified, so 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

*Musser, G.G. and Carleton, M.D. 2005. Superfamily Muroidea. Pp. 894–1531 in Wilson, D.E. and Reeder, D.M. (eds.)
Mammal Species of the World: a taxonomic and geographic reference. 3rd ed
Baltimore: The Johns Hopkins University Press, 2 vols., 2142 pp. *Patterson, B., Pardinas, U. and D'Elia, G. 2008. . In IUCN. IUCN Red List of Threatened Species. Version 2009.2.
www.iucnredlist.org
. Downloaded on January 12, 2010. *Rodríguez-Serrano, E., Hernández, C.E. and Palma, R.E. 2008. A new record and an evaluation of the phylogenetic relationships of ''Abrothrix olivaceus markhami'' (Rodentia: Sigmodontinae). Mammalian Biology 73(4):309–317. {{Taxonbar, from=Q305888 Abrothrix Mammals of Argentina Mammals of Chile Mammals of Patagonia Taxa named by George Robert Waterhouse Mammals described in 1837 Taxonomy articles created by Polbot Taxobox binomials not recognized by IUCN