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Sigmodon fulviventer
tawny-bellied cotton rat


By Jenny LaRoche

Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Mammalia
Order: Rodentia
Family: Cricetidae
Genus: Sigmodon
Species: Sigmodon fulviventer

Geographic Range

Sigmodon fulviventer (tawny-bellied cotton rat) is a native mammal of the nearctic range. It is found from New Mexico and the southeastern corner of Arizona southward into central Mexico along the Sierra Madre Mountain Range. ("Wild Animals of North America", 1979; Wilson and Ruff, 1999)

Biogeographic Regions
nearctic (Native )

Habitat

Sigmodon fulviventer inhabits grassy areas dotted with shrubby growth. The shrubs afford cover and allow dense growth of grasses. Currently, only scattered habitat patches that have been protected from heavy grazing exist. (Baker and Shump Jr, 1978; Davis and Schmidly, 1994)

Habitat Regions
temperate

Terrestrial Biomes
desert or dune ; savanna or grassland ; chaparral

Physical Description

Range mass
200 to 220 g
(7.05 to 7.75 oz)

Range length
223 to 270 mm
(8.78 to 10.63 in)

Sigmodon fulviventer is the largest of the cotton rats and is distinguished from other cotton rats by its large size and coloration. It is also known as the tawny-bellied cotton rat, due to the buff-brown color of its underside. A salt and pepper pattern is found on the dorsal portion of the pelage. The tail is consistently black, with small tail scales and a heavy coating of hair. (Baker and Shump Jr, 1978; Davis and Schmidly, 1994; "Sevilleta Long Term Ecological Research", 2002; Wilson and Ruff, 1999)

These animals weigh between 200 and 220 g. They measure 223 to 270 mm in length, with a tail length between 94 and 109 mm. The skull is arched, short and broad, and contains 16 teeth. The upper incisors are well developed, and the large molars have high crowns.

Sexual Dimorphism
sexes alike

Reproduction

No information was found on mating systems for S. fulvivener. Little is known about the mating systems of the genus. ("Sevilleta Long Term Ecological Research", 2002; Wilson and Ruff, 1999)

Breeding interval
These animals can breed approximately monthly during the breeding season.

Breeding season
Breeding peaks in late summer or fall.

Average number of offspring
7-9

Range gestation period
27 to 33 days

Range time to weaning
10 to 15 days

Average time to independence
2 weeks

Average age at sexual or reproductive maturity (female)
6 weeks

Average age at sexual or reproductive maturity (male)
6 weeks

Breeding is seasonal and peaks in late summer or fall. Gestation is between 27 and 33 days in length, and results in a litter size averaging between 7 and 9. Within 18 to 36 hours of birth, the babies of S. fulviventer are fully furred, able to walk, and have opened eyes. They are weaned in 10 to 15 days. The young leave the nest when they are about two weeks old and begin to breed at about six weeks of age. ("Sevilleta Long Term Ecological Research", 2002; Wilson and Ruff, 1999)

Key Reproductive Features
iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization ; viviparous

Sigmodon fulviventer constructs a nest woven out of grasses in which it resides and cares for their young. It is not clear whether the male helps to raise the offspring. The female nurses the precocious youngsters until they are between 10 and 15 days old. Shortly after, the young disperse. (Baker and Shump Jr, 1978; Wilson and Ruff, 1999)

Parental Investment
no parental involvement; precocial ; pre-fertilization (Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Protecting)

Lifespan/Longevity

Average lifespan
Status: wild

2 months

Maximum lifespan/longevity for S. fulviventer is not known. However, in the wild, they are not expected to live beyond 2 months of age. ("Sevilleta Long Term Ecological Research", 2002)

Behavior

Sigmodon fulviventer prefers tall grassy areas where nests and runways can be hidden. It is reported to be quite excitable and pugnacious. Individuals of this species quarrel frequently. (Baker and Shump Jr, 1978; Cahalane, 1954; "Sevilleta Long Term Ecological Research", 2002)

Key Behaviors
terricolous

Communication and Perception

No information was found on communication for S. fulviventer. However, as mammals, it is likely that they have the ability to perceive visual information, accoustic information, and scent cues. It is also likely that they use these in intraspecific communication. Tactile communication is likely to occur during fighting as well as between mothers and their offspring.

Communication Channels
visual ; tactile ; acoustic ; chemical

Perception Channels
visual ; acoustic

Food Habits

The diet of S. fulviventer consists largely of grasses and sedges, as well as cultivated grains and vegetables. It will also feed on insects, grasshoppers, and quail eggs. (Cahalane, 1954)

Animal Foods
birds; eggs; insects

Plant Foods
leaves; roots and tubers; seeds, grains, and nuts

Predation

Known Predators


Sigmodon fulviventer serves as a principle food for many predators such as coyotes. (Cahalane, 1954)

Ecosystem Roles

Sigmodon fulviventer is part of the small mammal food base for a number of carnivores and raptors. (Cahalane, 1954)

Economic Importance for Humans: Positive

Sigmodon fulviventer is the principal food of numerous predators, serving as a "buffer species" between predators and game birds. (Cahalane, 1954)

In captivity, cotton rats have been influential in developing therapeutic clinical intervention strategies for many viral infections of humans. Examples include influenza virus, respitory wyncytial, adenovirus, poliovirus, and parainfluenza virus. Current research studies are being conducted on cotton rats to see if they are succeptible to HIV and to try to relate them to human HIV research. (Langly, et al., 1998)

Positive Impacts
research and education

Economic Importance for Humans: Negative

The reproductive capacity of S. fulviventer is impressive, and when coupled with a plentiful food supply the populations of these rodents can explode. When this happens, farmers may suffer financial losses due to crop damage. These rats will eat all kinds of cultivated grains and vegetables. (Cahalane, 1954)

Negative Impacts
crop pest

Conservation Status

IUCN Red List [Link]
Lower Risk - Least Concern

US Federal List [Link]
No special status

CITES [Link]
No special status

Sigmodon fulviventer is not listed by CITES or IUCN.

For More Information

Find Sigmodon fulviventer information at

Contributors

Nancy Shefferly (editor), Animal Diversity Web Staff.

Jenny LaRoche (author), University of Wisconsin-Stevens Point, Chris Yahnke (editor, instructor), University of Wisconsin Stevens Point.

References

National Geographic Society. 1979. Wild Animals of North America. Washington D.C.: National Geographic Society.

University of New Mexico. 2002. "Sevilleta Long Term Ecological Research" (On-line ). Accessed 10/02/02 at http://sevilleta.unm.edu/data/species/mammal/socorro/profile/tawny-bellied-cotton-rat.html.

Baker, R., K. Shump Jr. 1978. Sigmodon fulviventer. Mammalian Species, 94: 1-4.

Cahalane, V. 1954. Mammals of North America. New York: Macmillan Company.

Davis, W., D. Schmidly. 1994. "The Mammals of Texas" (On-line ). Accessed 10/02/02 at http://www.nsrl.ttu.edu/tmot1/sigmfulv.htm.

Langly, R., G. Prince, H. Ginsberg. 1998. HIV type-1 Infection Of The Cotton Rat. Proc Natl Acad Sci USA, 95(24): 14355-60.

Wilson, D., S. Ruff. 1999. The Smithsonian Book of North American Mammals. Washington and London: Smithsonian Institution Press.

To cite this page: LaRoche, J. 2004. "Sigmodon fulviventer" (On-line), Animal Diversity Web. Accessed February 12, 2012 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Sigmodon_fulviventer.html

Disclaimer: The Animal Diversity Web is an educational resource written largely by and for college students. ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.

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