Southern Big-eared Mouse
Encyclopedia
The southern big-eared mouse (Loxodontomys micropus), also known as the southern pericote, is a species of rodent
in the family Cricetidae
. It is found in Argentina
and Chile
, and is one of only two species in its genus
. The type specimen was captured by Charles Darwin
in 1834 along the Santa Cruz River
in Argentina, during the voyage of the HMS Beagle
, and was subsequently described by George Robert Waterhouse
.
The fur is dull greyish-brown over most of the body, with paler greyish or yellowish underparts. As its name suggests. it has larger ears than many other local species of mouse, although they are not dramatically so. The feet are sturdy, and the fifth toe on the hind feet is unusually long. The tail is about three-quarters the length of the body, and is covered with sparse fur. It can most readily be distinguished from other nearby mouse species by its robust build, relatively long tail, and the absence of hair on the feet. Females have four pairs of teats, running from the axillary region down to the groin.
foothills of southern Chile and south-western Argentina, from about 38°S down to the Straits of Magellan. A few isolated populations are also known from hilly regions of south-central Argentina, and the species is also found on Chiloé Island
in Chile. It inhabits environments with heavy vegetation and good ground cover at elevations up to 3000 metres (9,842.5 ft). It is most commonly found in forests dominated by southern beech
trees, with dense undergrowth of South American bamboo
. However, it can also be found in bushy scrub, such as that formed by barberries
and Colletia
, and in humid grasslands.
, although it may sometimes be active during the day. They dig burrows with numerous entrances, and have been known to store food. It feeds primarily on leaves, seeds, and grasses, but also eats some fungi. Population densities have been reported to vary between 0.9 /ha, depending on the local environment and time of year, with more individuals being found in the autumn.
The most common predators of the species include various owls, such as barn owl
s, short-eared owl
s, and lesser horned owls. However, various other local predators, including lesser grison
s, zorros, and buzzard-eagle
s, may also include southern big-eared mice in their diets.
Southern big-eared mice breed throughout the spring and summer, and typically give birth to litters of four or five young. The young reach independence at a relatively early age, and those born in spring are generally reproductively active before the breeding season finishes in late summer. Individuals may be able to breed by the time they reach a body weight of 48 grams (1.7 oz), considerably less than the full adult size.
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 Cricetidae
Cricetidae
The Cricetidae are a family of rodents in the large and complex superfamily Muroidea. It includes true hamsters, voles, lemmings, and New World rats and mice...
. It is found in 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...
and 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 is one of only two species in its genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
. The type specimen was captured by Charles Darwin
Charles Darwin
Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...
in 1834 along the Santa Cruz River
Santa Cruz River (Argentina)
Santa Cruz River is a river from the Argentine province of Santa Cruz.The Santa Cruz begins at the shore of the Viedma and Argentino Lakes, of glacial origin and located in the Los Glaciares National Park, and runs eastwards before reaching the Atlantic Coast, north of the southern tip of South...
in Argentina, during the voyage of the HMS Beagle
HMS Beagle
HMS Beagle was a Cherokee-class 10-gun brig-sloop of the Royal Navy. She was launched on 11 May 1820 from the Woolwich Dockyard on the River Thames, at a cost of £7,803. In July of that year she took part in a fleet review celebrating the coronation of King George IV of the United Kingdom in which...
, and was subsequently described by George Robert Waterhouse
George Robert Waterhouse
George Robert Waterhouse was an English naturalist.In 1833, Waterhouse was elected as the Royal Entomological Society of London's librarian and curator of insects and records....
.
Description
The southern big-eared mouse has a relatively heavy build for a mouse, accentuated by its thick fur. Fully grown adults of both sexes range from 237 to 242 cm (93.3 to 95.3 ) in total length, including the tail, and weigh between 45 and 105 g (1.6 and 3.7 ). It is however, not unusual for individuals to reach sexual maturity long before they reach the full adult size.The fur is dull greyish-brown over most of the body, with paler greyish or yellowish underparts. As its name suggests. it has larger ears than many other local species of mouse, although they are not dramatically so. The feet are sturdy, and the fifth toe on the hind feet is unusually long. The tail is about three-quarters the length of the body, and is covered with sparse fur. It can most readily be distinguished from other nearby mouse species by its robust build, relatively long tail, and the absence of hair on the feet. Females have four pairs of teats, running from the axillary region down to the groin.
Distribution and habitat
The southern big-eared mouse is found in the AndeanAndes
The Andes is the world's longest continental mountain range. It is a continual range of highlands along the western coast of South America. This range is about long, about to wide , and of an average height of about .Along its length, the Andes is split into several ranges, which are separated...
foothills of southern Chile and south-western Argentina, from about 38°S down to the Straits of Magellan. A few isolated populations are also known from hilly regions of south-central Argentina, and the species is also found on Chiloé Island
Chiloé Island
Chiloé Island , also known as Greater Island of Chiloé , is the largest island of the Chiloé Archipelago off the coast of Chile, in the Pacific Ocean...
in Chile. It inhabits environments with heavy vegetation and good ground cover at elevations up to 3000 metres (9,842.5 ft). It is most commonly found in forests dominated by southern beech
Nothofagus
Nothofagus, also known as the southern beeches, is a genus of 35 species of trees and shrubs native to the temperate oceanic to tropical Southern Hemisphere in southern South America and Australasia...
trees, with dense undergrowth of South American bamboo
Chusquea
Chusquea is a genus of bamboo with about 150 species. Most of them are mountain clumping bamboos native from southern Mexico to southern Chile and Argentina. They are sometimes referred to as South American mountain bamboos. Unlike most other bamboos, the stems of these species are solid, not hollow...
. However, it can also be found in bushy scrub, such as that formed by barberries
Berberis
Berberis , the barberries or pepperidge bushes, is a genus of about 450-500 species of deciduous and evergreen shrubs from 1-5 m tall with thorny shoots, native to the temperate and subtropical regions of Europe, Asia, Africa, North America and South America. They are closely related to the genus...
and Colletia
Colletia
Colletia is a genus of flowering plants in the family Rhamnaceae, with 15 to 17 species of spiny shrubs. All species of this genus are native to southern South America. They are non-legume nitrogen fixers.-Selected species:*Colletia armata...
, and in humid grasslands.
Subspecies
Three subspecies are currently recognised, and can be distinguished by subtle variations in the colour of the coat and feet:- Loxodonta micropus micropus
- Loxodonta micropus alsus
- Loxodonta micropus fumipes - Chiloé Island
Biology
The southern big-eared mouse is a nocturnal herbivoreHerbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
, although it may sometimes be active during the day. They dig burrows with numerous entrances, and have been known to store food. It feeds primarily on leaves, seeds, and grasses, but also eats some fungi. Population densities have been reported to vary between 0.9 /ha, depending on the local environment and time of year, with more individuals being found in the autumn.
The most common predators of the species include various owls, such as barn owl
Barn Owl
The Barn Owl is the most widely distributed species of owl, and one of the most widespread of all birds. It is also referred to as Common Barn Owl, to distinguish it from other species in the barn-owl family Tytonidae. These form one of two main lineages of living owls, the other being the typical...
s, short-eared owl
Short-eared Owl
The Short-eared Owl is a species of typical owl . In Scotland this species of owl is often referred to as a cataface, grass owl or short-horned hootlet. Owls belonging to genus Asio are known as the eared owls, as they have tufts of feathers resembling mammalian ears. These "ear" tufts may or may...
s, and lesser horned owls. However, various other local predators, including lesser grison
Lesser Grison
The lesser grison , Galictis cuja, is a mammal species of the ferret family Mustelidae from South America. It is found in Argentina, Bolivia, Brazil, Chile, Paraguay, Peru, and Uruguay....
s, zorros, and buzzard-eagle
Black-chested Buzzard-eagle
The Black-chested Buzzard-Eagle is a bird of prey of the hawk and eagle family . It lives in open regions of South America. This species is also known as the Black Buzzard-eagle, Grey Buzzard-eagle or analogously with "eagle" or "eagle-buzzard" replacing "buzzard-eagle", or as the Chilean Blue Eagle...
s, may also include southern big-eared mice in their diets.
Southern big-eared mice breed throughout the spring and summer, and typically give birth to litters of four or five young. The young reach independence at a relatively early age, and those born in spring are generally reproductively active before the breeding season finishes in late summer. Individuals may be able to breed by the time they reach a body weight of 48 grams (1.7 oz), considerably less than the full adult size.