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 ; tactile ; acoustic ; chemical
Sigmodon fulviventer is not listed by CITES or IUCN.
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: least concern
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.
Negative Impacts: crop pest
Sigmodon fulviventer is the principal food of numerous predators, serving as a "buffer species" between predators and game birds.
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.
Positive Impacts: research and education
Sigmodon fulviventer is part of the small mammal food base for a number of carnivores and raptors.
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.
Animal Foods: birds; eggs; insects
Plant Foods: leaves; roots and tubers; seeds, grains, and nuts
Primary Diet: omnivore
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.
Biogeographic Regions: nearctic (Native )
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.
Habitat Regions: temperate
Terrestrial Biomes: desert or dune ; savanna or grassland ; chaparral
Maximum lifespan/longevity for S. fulviventer is not known. However, in the wild, they are not expected to live beyond 2 months of age.
Status: wild: 2 months.
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.
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.
Range mass: 200 to 220 g.
Range length: 223 to 270 mm.
Sexual Dimorphism: sexes alike
Other Physical Features: endothermic ; bilateral symmetry
Sigmodon fulviventer serves as a principle food for many predators such as coyotes.
No information was found on mating systems for S. fulvivener. Little is known about the mating systems of the genus.
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.
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 weaning age: 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.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; 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.
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)
Sexual dimorphism is not present, but the adult male weighs slightly more than the female at 222 grams (7.8 oz) compared to 206 grams (7.3 oz). The tail has small scales and is covered in hair which distinguishes it from the larger scales of the closely related hispid cotton rat (Sigmodon hispidus). Another characteristic distinguishing it from S. hispidus is a short and broad rather than elongated skull. The dentition is marked by well-developed maxillary incisors and high-crowned molars.
The fur is tawny on the belly (the origin of the species' common name), and black and tan speckled on the back. The fur body contains three types of hair: guard-awl hair, guard hair, and under hair. The guard hair is the longest with the guard-awl and under hair following in decreasing length. Whiskers are located on the face and have been observed to play a role in maintaining body position while swimming.
The species inhabits the grasslands of central Mexico, expanding north to the central and southwestern parts of New Mexico and southeastern parts of Arizona. It prefers areas with dense grass, in which it makes navigational trails called runways that resemble a tunnel with a grass covering. It feeds on grasses, specifically bunchgrass, which they also use in nest-building. Its range in central New Mexico is expanding westward due to an increase in precipitation and in temperature from climate change.
The tawny-bellied cotton rat occurs in the same area as the closely related hispid cotton rat, with the former occupying the moister areas and the latter the more arid areas. When living in adjacent habitats, one species tends to become more numerous while the other maintains a smaller population. Even though both species seem to avoid one another, there is a passive, indirect competition between the species. In Durango, Mexico, S. fulviventer was found to be dominant, probably due to being a specialist compared to the generalist S. hispidus.
The tawny-bellied cotton rat is used as a model organism to develop and test human pathogen treatments. It is affected by many of the same viral and bacterial infections that humans are susceptible to, which helps create vaccines and therapeutic treatments. Other factors that make the species a desirable test subject are the existence of inbred strains, ease of handling, and inexpensive upkeep. Some of the diseases tested on the cotton rat are respiratory syncytial virus, and pulmonary tuberculosis, and HIV type-1.
In the case of HIV type-1, finding an animal with similar antibody response to the virus as humans can prove difficult. A study conducted in 1998 found that the tawny-bellied cotton rat can be infected by low-level HIV-1. A similar immune response to humans is activated on infection. The degree of infection may be increased by altering the co-receptors on the animal's cells, which would improve the reliability of the test subject.
The species was found to undergo an equivalent infection to pulmonary tuberculosis as humans. This is an upgrade over the previous animal models of other small rodents and rabbits. Cotton rats combine the best traits of human-like lung granuloma formation (trait of rabbits) and inexpensive care (trait of other small rodents) to provide a suitable host for this type of study. Future research is underway to use the cotton rat for studying pulmonary tuberculosis complicated by HIV-1 due to similarities with humans in both diseases.