The southern cotton rat (''Sigmodon hirsutus'') is a

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 ...

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

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 southern

Chiapas Chiapas (; Tzotzil language, Tzotzil and Tzeltal language, Tzeltal: ''Chyapas'' ), officially the Free and Sovereign State of Chiapas ( es, Estado Libre y Soberano de Chiapas), is one of the states that make up the Political divisions of Mexico, ...

in Mexico through Central America, except for Belize, and as far east as northern Colombia and Venezuela. It lives in

tropical rainforest Tropical rainforests are rainforests that occur in areas of tropical rainforest climate in which there is no dry season – all months have an average precipitation of at least 60 mm – and may also be referred to as ''lowland equatori ...

dry forest Dry or dryness most often refers to: * Lack of rainfall, which may refer to **Arid regions **Drought * Dry or dry area, relating to legal prohibition of selling, serving, or imbibing alcoholic beverages * Dry humor, deadpan * Dryness (medical) ...

and

savanna A savanna or savannah is a mixed woodland-grassland (i.e. grassy woodland) ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to ...

, as well as in cultivated areas. The species is terrestrial and primarily diurnal. It was long thought to be a subspecies of '' S. hispidus''. However, recent taxonomic revisions, based on

mitochondrial DNA Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial D ...

sequence data, have split the extensive former species range into three separate species. Carroll et al. (2004) indicate that the southern edge of the ''S. hispidus'' distribution is likely near the Rio Grande where it meets the northern distribution of '' S. toltecus'' (formerly ''S. h. toltecus''). The range of ''S. toltecus'' extends from northern Mexico south into

where it occurs in

sympatry 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 ''S. hirsutus'' (formerly ''S. h. hirsutus''). Rats from this species group have been used as laboratory animals.

References

*Carroll, D. S., L. L. Peppers, and R. D. Bradley. 2004. Molecular systematics and phylogeography of the ''Sigmodon hispidus'' species group. pp. 85–98, in Contribuciones Mastozoologicas en Homenaje a Bernardo Villa (Sanchez-Cordero V. y R. A. Medellin Eds.) Instituto de Biologia e Instituto de Ecologia, UNAM, Mexico. Cotton rats Mammals of Colombia Rodents of Central America Mammals described in 1854 {{Sigmodon-stub