Hispid cotton rats are small to medium sized rodents, with adults weighing 100 to 225 g (average 159 g). Total length ranges from 80 to 320 mm, with males slightly longer than females. Regional size variation exists; hispid cotton rats in Virginia are smaller than those found in North and South Carolina. The color of both sexes consists of a mixture of tan, brown, and black fur on their dorsal parts, giving them a coarse, or "hispid," appearance. The underparts are white to greyish, the tail is sparsely haired and considerably shorter than the combined length of the head and body. Regional variation in color is common, hispid cotton rats from the Coastal Plain of North and South Carolina are darker than those from Maryland and Virginia. (Choate, et al., 1994; Linzey, 1998; Mengak and Laerm, 2007; Schwartz and Schwartz, 1981; Webster, et al., 1985)
Hispid cotton rats have an extensive range. The southern range reaches northern South America in Peru, Ecuador, Columbia, Venezuela, Guyana, French Guiana, and Brazil. The range extends northward through central America and Mexico. In the United States, they are found as far north as Nebraska in the west and coastal and central Virginia to the east. In the past 50 to 100 years hispid cotton rats have been extending their range northward and to higher elevations. (Cameron and Spencer, 1981; Cameron, 1999; Choate, et al., 1994; Dunnum, et al., 2002; Francl and Meikle, 2009)
Hispid cotton rats prefer dense, grassy areas. They are most commonly captured in grassy fields, brushy pastures, canal banks, roadsides, and edges of cultivated fields overgrown with weeds and other brushy vegetation such as broomsedge and honeysuckle. They occasionally have been observed in areas of dense cacti, salt marshes, and in grasslands bordering brackish waters. In Mexico, hispid cotton rats range from sea level to 1130 m in elevation. (Cameron and Spencer, 2008; Espinoza and Rowe, 1979; Linzey, 1998; Rehmeier, et al., 2005; Schwartz and Schwartz, 1981; Webster, et al., 1985)
Little has been published about the mating systems of hispid cotton rats, though they are assumed to be polygamous, meaning one male mates with multiple females. (Sulok, et al., 2004)
In tropical and semi-tropical portions of their range, hispid cotton rats breed year-round. In temperate regions, however, breeding seems to be determined by temperature. In non-pregnant females heat occurs about every 7 to 9 days. The gestation period is about 27 days. A single adult female typically produces 3 to 4 litters per year, averaging 5 to 7 young per litter. Newborns average 76 mm in total length and 6.5 g. They are usually weaned at about 3 weeks and can be reproductively active in 35 to 40 days. However, most do not reproduce until 2 months. Hispid cotton rats are fully grown at 5 months of age. (Espinoza and Rowe, 1979; Linzey, 1998; Schwartz and Schwartz, 1981; Webster, et al., 1985)
Female hispid cotton rats produce more than one litter per year. The young stay in the nest until they are about 3 weeks old when they are weaned and begin to care for themselves. (Linzey, 1998)
Hispid cotton rats, like many rodents, are not long lived in the wild. Few cotton rats (13.2%) live beyond six months. The oldest recorded Sigmodon species individual lived 12 months in the wild. In captivity, the oldest hispid cotton rat recorded is five years, two months old. (Linzey, 1998)
Hispid cotton rats are active year-round and during all hours of the day. Maximum activity is concentrated from late afternoon to about midnight. They are less active during heavy rains and extreme cold.Hispid cotton rats are generally solitary, but also show cooperative behavior in cooler months, huddling together for warmth. During the breeding season, older males display dominance over younger males. Members of this species also tend to be aggressive towards other rodent species occupying the same habitat.
Hispid cotton rats construct nests using dry grass, fibers stripped from larger plants, and other materials. Nests are built under logs and rocks for protection. Sometimes they use abandoned dens of larger mammals such as skunks or squirrels. They also construct a maze of runways, about 7.5 to 10 cm wide, and tunnels from 2.5 to 5 cm wide and from 2.5 to 10 cm below the surface. New growth of grasses and sedges is trimmed from main runways and trimmings are piled up in an irregular manner. (Cameron and Spencer, 1981; Linzey, 1998; Schwartz and Schwartz, 1981)
Hispid cotton rats have a home ranges from 0.10 to 0.50 ha. Males usually have larger home ranges (0.40 to 0.50 ha) than females (0.10 to 0.30 ha). Adult home ranges are larger than those of young adults or juveniles. Movements are typically less than 100 m per day, but can be upwards of 300 m in rare cases. They typically do not defend territories, but there have been reports that females may occasionally do so. (Cameron and Spencer, 1981; Espinoza and Rowe, 1979; Linzey, 1998; Schwartz and Schwartz, 1981)
Little information regarding communication of hispid cotton rats has been reported. However, like most mammals, hispid cotton rats have a keen sense of smell and hearing. (Cameron and Spencer, 1981)
Hispid cotton rats are folivorous, granivorous, and lignivorous. In addition they feed on the eggs and young of ground-nesting birds, insects, crayfish, fiddler crabs, and carrion where possible. They do not cache food. When feeding on tall plants they cut down the plant near its base then cut the whole plant into smaller sections. They drink water but do not require a permanent water source in their habitat. (Linzey, 1998; Schwartz and Schwartz, 1981)
Hispid cotton rats avoid predation by staying in their runways, being alert, and taking advantage of their cryptic coloration. Hispid cotton rats are preyed on by a wide variety of predators including fire ants, owls, hawks, red foxes, bobcats, raccoons, coyotes, domestic cats, weasels, mink, and snakes. (Cameron and Spencer, 1981; Ferris, 1994; Pedersen, et al., 2003)
Hispid cotton rats have an important relationship with bobwhite quail (Colinus virginianus) because they compete with quail for food resources and feed on the quail eggs. In addition, hispid cotton rats are host to many internal and external parasites. External parasites are hosts to mites, ticks, lice, and fleas. They are also hosts to cestode species (Choanotaenia nebraskensis, Hymenolepis diminuta, Raillietina bakeri, Taenia taeniaeformis), bacteria (Rickettsia rickettsii), nematodes (Longistriata adunca, Physaloptera hispida, Mastophorus muris), and ascarid worms. (Linzey, 1998; Mengak and Laerm, 2007; Schwartz and Schwartz, 1981)
Hispid cotton rats can greatly reduce crop production. They cause damage to a variety of crops, including cotton, rice, alfalfa, grains, vegetables, fruits, squash, sugarcane, corn, sweet potatoes, and melons. Dense populations of hispid cotton rats also cause damage to canal banks. (Espinoza and Rowe, 1979)
There is no evidence hispid cotton rats are economically beneficial.
Over much of their range hispid cottons rats are common and populations are stable. In Kentucky hispid cotton rats are listed as vulnerable because they occur in only a portion of the state, in portions of just 8 counties in the southwestern and southeastern corners. (Mengak and Laerm, 2007)
Dwight Meikle (author), Radford University, Karen Powers (author, editor), Radford University, Gail McCormick (editor), Animal Diversity Web Staff, Tanya Dewey (editor), University of Michigan-Ann Arbor.
Anderson, A., J. Mithchell, J. Pagels, H. Mansfield. 2001. Mammals of Fort A. P. Hill, Caroline County, Virginia and Vicinity. Virginia Journal of Science, 52: 163-226.
Cameron, G. 1999. The Smithsonian Book of North American Mammals. Washington: Smithsonian Institution Press.
Cameron, G., S. Spencer. 2008. Mechanisms of Habitat Selection by the Hispid Cotton Rat (Sigmodon hispidus). Journal of Mammalogy, 89/1: 126-131.
Cameron, G., S. Spencer. 1981. Sigmodon hispidus. Mammalian Species, 158: 1-9.
Choate, J., J. Jones, Jr., C. Jones. 1994. Handbook of Mammals of the South-Central States. Baton Rouge: Louisiana State University Press.
Dunnum, J., J. Frey, D. Tinnin, J. Salazar-Bravo, T. Yates. 2002. Elevational Range Extension for the Hispid Cotton Rat, Sigmodon hispidus, (Rodentia: Muridae). Southwester Naturalist, 47: 637-639.
Espinoza, H., F. Rowe. 1979. Biology and Control of the Cotton Rat, Sigmodon hispidus. International Journal of Pest Management, 25/3: 251-256.
Ferris, K. 1994. Parental responses of hispid cotton rats (Sigmodon hispidus) to intrusion by red imported fire ants (Solenopsis invicta) into simulated nests - M.S. Thesis. College Station, TX: Texas A & M University.
Francl, K., D. Meikle. 2009. A Range Extension of the Hispid Cotton Rat, Sigmodon hispidus, in Virginia. Banisteria, 33: 54-55.
Genoways, H., D. Schlitter. 1966. Northward dispersal of the Hispid Cotton Rat in Nebraska and Missouri. Transactions of the Kansas Academy of Science, 69: 356-357.
Linzey, D. 1998. The Mammals of Virgina. Blacksburg, Va: The McDonald and Woodward Publishing Company.
Mengak, M., J. Laerm. 2007. Hispid Cotton Rat. Pp. 374-380 in M Trani, W Ford, B Chapman, eds. The Land Managers Guide to Mammals of the South. Atlanta: USDA Forest Service and The Nature Conservancy.
Pagels, J. 1977. Distribution and habitat of cotton rat (Sigmodon hispidus) in Central Virginia. Virginia Journal of Science, 28: 133-153.
Pedersen, E., T. Bedford, W. Grant, S. Vinson, J. Martin, M. Longnecker, C. Barr, B. Drees. 2003. Effect of Red Imported Fire Ants on Habitat Use by Hispid Cotton Rats (Sigmodon hispidus) and Northern Pygmy Mice (Baiomys taylori) Effect of Red Imported Fire Ants on Habitat Use by Hispid Cotton Rats (Sigmodon hispidus) and Northern Pygmy Mice (Baiomys taylori). Southwestern Naturalist, 48/3: 419-426.
Rehmeier, R., G. Kaufman, D. Kaufman, B. McMillan. 2005. Long-Term Study of Abundance of the Hispid Cotton Rat in Native Tallgrass Prairie. Journal of Mammalogy, 86/4: 670-676.
Schwartz, C., E. Schwartz. 1981. The Wild Mammals of Missouri. Columbia: University of Missouri Press.
Sulok, M., N. Slade, T. Doonan. 2004. Effects of Supplemental Food on Movements of Cotton Rats (Sigmodon hispidus) in Northeastern Kansas. Journal of Mammalogy, 85/6: 1102-1105.
Webster, W., J. Parnell, W. Biggs, Jr.. 1985. Mammals of the Carolinas, Virginia, and Maryland. Chapel Hill: The University of North Carolina Press.