Viscacha Rat
Encyclopedia
The viscacha rat or mountain viscacha rat, is a species of rodent
in the family Octodontidae
. It is endemic to Chile
and Argentina
.
It is the only living species within the genus Octomys. This diploid genus (2n = 56) may be ancestral to the two unusual tetraploid
species Tympanoctomys barrerae and Pipanacoctomys aureus.
Unusual features of the viscacha rat include greatly enlarged auditory bulla
e, and the presence of numerous whisker
s on the roof of the mouth behind the incisor
teeth. The exact function of the whiskers is unclear, but they may enable the animal to sense the position of food inside the mouth.
region of northwestern Argentina
, specifically in the provinces of Catamarca
, La Rioja
, San Luis
, San Juan
, and possibly Mendoza
. They inhabit rocky desert and semidesert environments up to 800 metres (2,624.7 ft) above sea level.
close to crevice entrances to help protect against predators. Individuals occupy large home ranges of around 12300 square metres (3 acre), often overlapping with those of their neighbours. They are herbivorous, feeding on the leaves and seeds of shrubland vegetation. During the dry season, their diet consists largely of the leaves of Prosopis
trees, supplemented by caperbushes
and alkaliweeds
. During the wet season, they eat more seeds and fruit, including those from plants such as Maytenus
and boxthorn
shrubs.
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....
in the family Octodontidae
Octodontidae
The Octodontidae are a family of rodents, restricted to south-western South America. Thirteen species of octodontid are recognised, arranged in nine genera. The best known species is the Degu, Octodon degus....
. It is endemic to Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
and Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
.
It is the only living species within the genus Octomys. This diploid genus (2n = 56) may be ancestral to the two unusual tetraploid
Ploidy
Ploidy is the number of sets of chromosomes in a biological cell.Human sex cells have one complete set of chromosomes from the male or female parent. Sex cells, also called gametes, combine to produce somatic cells. Somatic cells, therefore, have twice as many chromosomes. The haploid number is...
species Tympanoctomys barrerae and Pipanacoctomys aureus.
Description
The viscacha rat is a rat-like animal with a head-body length of 11 to 18 cm (4.3 to 7.1 in) and weighing from 85 to 121 g (3 to 4.3 oz). The feet are relatively long, while the tail measures 12 to 16 cm (4.7 to 6.3 in). It has light brown fur with white underparts and a bushy tail.Unusual features of the viscacha rat include greatly enlarged auditory bulla
Auditory bulla
The auditory bulla is a hollow bony structure on the ventral, posterior portion of the skull of placental mammals that encloses parts of the middle and inner ear. In most species, it is formed by the tympanic part of the temporal bone.In extant primates, the structure is found in tarsiers,...
e, and the presence of numerous whisker
Whisker
Whisker may refer to:* an element of box plots* cat's whisker diode, a thin wire used as a contact on a crystal radio receiver* facial hair, hair on the face of a human* vibrissa, a hair on the face of a mammal, used for sensing the surroundings...
s on the roof of the mouth behind the incisor
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
teeth. The exact function of the whiskers is unclear, but they may enable the animal to sense the position of food inside the mouth.
Distribution and habitat
Viscacha rats are found only in the Monte DesertMonte Desert
The Monte Desert is a South American desert, located within the country of Argentina. The desert lies southeast of the Atacama Desert in Chile, north of the larger Patagonian Desert, and east of the Andes.-Geography and climate:...
region of northwestern Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
, specifically in the provinces of Catamarca
Catamarca Province
Catamarca is a province of Argentina, located in the northwest of the country. The province has a population of 334,568 as per the , and covers an area of 102,602 km². Its literacy rate is 95.5%. Neighbouring provinces are : Salta, Tucumán, Santiago del Estero, Córdoba, and La Rioja...
, La Rioja
La Rioja Province (Argentina)
La Rioja is a one of the provinces of Argentina and is located in the west of the country. Neighboring provinces are from the north clockwise Catamarca, Córdoba, San Luis and San Juan.-History:...
, San Luis
San Luis Province
San Luis is a province of Argentina located near the geographical center of the country . Neighboring provinces are, from the north clockwise, La Rioja, Córdoba, La Pampa, Mendoza and San Juan.-History:...
, San Juan
San Juan Province (Argentina)
San Juan is a province of Argentina, located in the western part of the country. Neighbouring provinces are, moving clockwise from the north, La Rioja, San Luis and Mendoza. It borders with Chile at the west....
, and possibly Mendoza
Mendoza Province
The Province of Mendoza is a province of Argentina, located in the western central part of the country in the Cuyo region. It borders to the north with San Juan, the south with La Pampa and Neuquén, the east with San Luis, and to the west with the republic of Chile; the international limit is...
. They inhabit rocky desert and semidesert environments up to 800 metres (2,624.7 ft) above sea level.
Behaviour
Viscacha rats are nocturnal and solitary, spending the day sheltering in rock crevices. Although it does not construct burrows, it may place pieces of cactusCactus
A cactus is a member of the plant family Cactaceae. Their distinctive appearance is a result of adaptations to conserve water in dry and/or hot environments. In most species, the stem has evolved to become photosynthetic and succulent, while the leaves have evolved into spines...
close to crevice entrances to help protect against predators. Individuals occupy large home ranges of around 12300 square metres (3 acre), often overlapping with those of their neighbours. They are herbivorous, feeding on the leaves and seeds of shrubland vegetation. During the dry season, their diet consists largely of the leaves of Prosopis
Prosopis
Prosopis is a genus of flowering plants in the pea family, Fabaceae. It contains around 45 species of spiny trees and shrubs found in subtropical and tropical regions of the Americas, Africa, Western Asia, and South Asia. They often thrive in arid soil and are resistant to drought, on occasion...
trees, supplemented by caperbushes
Capparis
Capparis is a flowering plant genus in the family Capparaceae which is included in the Brassicaceae in the unrevised APG II system. These plants are shrubs or lianas and are collectively known as caper shrubs or caperbushes...
and alkaliweeds
Cressa (genus)
Cressa is a genus of plants in the morning glory family known generally as alkaliweeds. These plants are native to the tropical and subtropical areas of the world. They are clumpy and low-growing but usually have erect stems covered white-haired, green leaves...
. During the wet season, they eat more seeds and fruit, including those from plants such as Maytenus
Maytenus
Maytenus is a genus of flowering plants in the staff vine family, Celastraceae. Members of the genus are distributed throughout Central and South America, Southeast Asia, Micronesia and Australasia, the Indian Ocean and Africa...
and boxthorn
Boxthorn
Boxthorn is a genus of the nightshade family , containing about 90 species of plants native throughout much of the temperate and subtropical zones of the world...
shrubs.