The southern cotton rat, Sigmodon hirsutus, is a rodent

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....

 species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 in the family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 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 southern Chiapas

Chiapas

Chiapas officially Estado Libre y Soberano de Chiapas is one of the 31 states that, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 118 municipalities and its capital city is Tuxtla Gutierrez. Other important cites in Chiapas include San Cristóbal de las...

 in Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

 through Central America

Central America

Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...

, except for Belize

Belize

Belize is a constitutional monarchy and the northernmost country in Central America. Belize has a diverse society, comprising many cultures and languages. Even though Kriol and Spanish are spoken among the population, Belize is the only country in Central America where English is the official...

, and as far east as northern Colombia

Colombia

Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...

 and Venezuela

Venezuela

Venezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...

. It lives in tropical rainforest

Tropical rainforest

A tropical rainforest is an ecosystem type that occurs roughly within the latitudes 28 degrees north or south of the equator . This ecosystem experiences high average temperatures and a significant amount of rainfall...

, dry forest

Tropical and subtropical dry broadleaf forests

The tropical and subtropical dry broadleaf forest biome, also known as tropical dry forest, is located at tropical and subtropical latitudes. Though these forests occur in climates that are warm year-round, and may receive several hundred centimeters of rain per year, they have long dry seasons...

 and savanna

Savanna

A savanna, or savannah, is a grassland ecosystem characterized by the trees being sufficiently small or widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of C4 grasses.Some...

, as well as in cultivated areas. The species is terrestrial and primarily diurnal. It was long thought to be a subspecies of S. hispidus

Hispid Cotton Rat

The Hispid Cotton Rat is a rodent species long thought to occur in parts of South America, Central America, and southern North America. However, recent taxonomic revisions, based on mitochondrial DNA sequence data, have split this widely distributed species into three separate species. Carroll et...

. However, recent taxonomic revisions, based on mitochondrial DNA

Mitochondrial DNA

Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...

 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

Toltec cotton rat

The Toltec cotton rat, Sigmodon toltecus, is a rodent species in the family Cricetidae. It is found in eastern Mexico from the Rio Grande to the Yucatán Peninsula, as well as in Belize and northern Guatemala. It prefers moist grassland habitat. While long thought to be a subspecies of S...

(formerly S. h. toltecus). The range of S. toltecus extends from northern Mexico south into Chiapas

Chiapas

Chiapas officially Estado Libre y Soberano de Chiapas is one of the 31 states that, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 118 municipalities and its capital city is Tuxtla Gutierrez. Other important cites in Chiapas include San Cristóbal de las...

 where it occurs in sympatry

Sympatry

In biology, two species or populations are considered sympatric when they exist in the same geographic area and thus regularly encounter one another. An initially-interbreeding population that splits into two or more distinct species sharing a common range exemplifies sympatric speciation...

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