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.
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.
- Habitat Regions
- temperate
- Terrestrial Biomes
- desert or dune
- savanna or grassland
- chaparral
Physical Description
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.
- Other Physical Features
- endothermic
- bilateral symmetry
- 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.
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.
- 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
-
protecting
-
pre-hatching/birth
-
provisioning
- female
-
protecting
- female
-
provisioning
-
pre-weaning/fledging
-
provisioning
- female
-
protecting
- female
-
provisioning
-
pre-independence
- protecting
Lifespan/Longevity
Maximum lifespan/longevity for
S. fulviventer
is not known. However, in the wild, they are not expected to live beyond 2 months
of age.
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.
- Key Behaviors
- terricolous
- motile
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.
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.
- Primary Diet
- omnivore
- Animal Foods
- birds
- eggs
- insects
- Plant Foods
- leaves
- roots and tubers
- seeds, grains, and nuts
Predation
Sigmodon fulviventer
serves as a principle food for many predators such as coyotes.
Ecosystem Roles
Sigmodon fulviventer
is part of the small mammal food base for a number of carnivores and raptors.
Economic Importance for Humans: Positive
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
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.
- Negative Impacts
- crop pest
Conservation Status
Sigmodon fulviventer is not listed by CITES or IUCN.
Additional Links
Contributors
Nancy Shefferly (editor), Animal Diversity Web.
Jenny LaRoche (author), University of Wisconsin-Stevens Point, Chris Yahnke (editor, instructor), University of Wisconsin-Stevens Point.
- Nearctic
-
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- temperate
-
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
- desert or dunes
-
in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.
- tropical savanna and grassland
-
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
- savanna
-
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
- temperate grassland
-
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
- chaparral
-
Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.
- iteroparous
-
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
- seasonal breeding
-
breeding is confined to a particular season
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- fertilization
-
union of egg and spermatozoan
- viviparous
-
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
- young precocial
-
young are relatively well-developed when born
- motile
-
having the capacity to move from one place to another.
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- omnivore
-
an animal that mainly eats all kinds of things, including plants and animals
- endothermic
-
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
- bilateral symmetry
-
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
References
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.
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 .