The Arizona cotton rat or Colorado River cotton rat (''Sigmodon arizonae'') 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 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 in

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

and the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

Description

The Arizona cotton rat has a typical

rat Rats are various medium-sized, long-tailed rodents. Species of rats are found throughout the order Rodentia, but stereotypical rats are found in the genus ''Rattus''. Other rat genera include ''Neotoma'' ( pack rats), ''Bandicota'' (bandicoot ...

-like appearance, and is sufficiently similar to the

hispid cotton rat The hispid cotton rat (''Sigmodon hispidus'') 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 ...

that it was considered to be part of the same species until 1970, when genetic analysis confirmed its distinct nature. It has bristly brownish fur over most of its body, with whitish underparts and grey feet. The scaly tail is dark in color, with very sparse fur. Adults range from in total length, including the long tail, and weigh anything from . Males are slightly larger than females, but the two sexes are otherwise similar in appearance. Females have ten or twelve teats, suggesting a maximum litter size of around this number. Reproduction is thought to occur year-round.

Distribution and habitat

The Arizona cotton rat is found in southern and central

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...

, the extreme southwestern corner of

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Tiguex , OfficialLang = None , Languages = English, Spanish ( New Mexican), Navajo, Ker ...

, and in western

from

Sonora Sonora (), officially Estado Libre y Soberano de Sonora ( en, Free and Sovereign State of Sonora), is one of the 31 states which, along with Mexico City, comprise the Administrative divisions of Mexico, Federal Entities of Mexico. The state is d ...

Nayarit Nayarit (), officially the Free and Sovereign State of Nayarit ( es, Estado Libre y Soberano de Nayarit), is one of the 31 states that, along with Mexico City, comprise the Federal Entities of Mexico. It is divided in 20 municipalities and its ...

. They live close to rivers, streams, and other sources of fresh water in

semidesert A semi-arid climate, semi-desert climate, or steppe climate is a dry climate sub-type. It is located on regions that receive precipitation below potential evapotranspiration, but not as low as a desert climate. There are different kinds of semi-ar ...

, open grassland, or swampy habitats throughout the region. They rely particularly on areas of dense grassy vegetation. Two of the five recognized

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 believed to have gone extinct during the twentieth century, including the nominate subspecies, ''Sigmodon arizonae arizonae''. Three subspecies therefore remain: * ''Sigmodon arizonae cienegae'' - Arizona, northern Sonora * ''Sigmodon arizonae major'' - southern Sonora,

Sinaloa Sinaloa (), officially the Estado Libre y Soberano de Sinaloa ( en, Free and Sovereign State of Sinaloa), is one of the 31 states which, along with Mexico City, comprise the Administrative divisions of Mexico, Federal Entities of Mexico. It is d ...

, Nayarit * ''Sigmodon arizonae plenus'' - western

La Paz County, Arizona La Paz County is the 15th county in the U.S. state of Arizona, located in the western part of the state. As of the 2020 census, its population was 16,557, making it the second-least populous county in Arizona. The county seat is Parker. Th ...

References

Cotton rats Mammals described in 1890 Taxonomy articles created by Polbot {{Sigmodon-stub