COTTON RATS
Identification
The hispid cotton rat (Sigmodon hispidus) is a moderately large, robust rodent with a scaly, sparsely haired tail that is shorter than the combined head and body.
Cotton rats have relatively large eyes. The ears are large but almost hidden in the fur. They have four toes and a small thumb on their front feet and five toes on each hind foot. The cotton rat has very small internal cheek pouches. Distinguishing characteristics are the rough grizzled appearance of the blackish or grayish fur and the rather stiff black guard hairs. This rodent has a high "Roman" nose and color similar to that of a javelina , resulting in the name " javelina rat" in many areas.
The total length averages 10 inches (25 cm) including the tail length of 4 inches (10 cm). The cotton rat may be distinguished from the Norway rat by its smaller size, shorter tail, and longer grizzled fur. Evidence of cotton rat presence are stem and grass cuttings 2 or 3 inches (5 or 8 cm) in length piled at various locations along runways, which are 3 to 5 inches (8 to 13 cm) wide. Pale greenish or yellow droppings, about 3/8 inch (9 mm) in length and 3/16 inch (5 mm) in diameter, may also be present along the runways.
Range
The hispid cotton rat occurs over most of the southern United States, from the southeastern tip of California, southern Arizona and New Mexico, north to eastern Colorado, eastward through the southern portions of Kansas and Missouri, through Tennessee and North Carolina, and southward along the Atlantic coast through Florida, the Gulf states, and up the Rio Grande Valley.
Two other species of cotton rat, the least cotton rat (S. minimus ) and the yellownose cotton rat (S. ochrognathus ) , occur only in small areas of southeastern Arizona and southwestern New Mexico . They are very similar to the hispid cotton rat.
Habitat
Cotton rats prefer dense cover such as grassy fields, overgrown roadsides, or fencerow vegetation adjacent to cultivated fields. They also occupy meadows, marshy areas, cactus patches, and weedy ditch banks. Under the protective cover, the cotton rat will have well-defined runways radiating in all directions from the nest site.
Food Habits
Cotton rats are normally herbivores, eating the roots, stems, leaves, and seeds of a wide variety of plants. They also feed on sugarcane, fruits, berries, and nuts. Cotton rats will cut tall plants off at the base and continue to cut them into shorter sections. They also eat insects, the eggs and young of ground-nesting birds (particularly quail), and the carcasses of dead animals.
General Biology, Reproduction, and Behavior
Cotton rats are basically nocturnal but will venture out in the daytime and are active year-round. The home range is small - from 1/4 to 3/4 acre (0.1 to 0.3 ha) for females and 1 to 1 1/4 acres (0.4 to 0.5 ha) for males. Cotton rats do not store food or hibernate. They can swim and do not hesitate to do so. This species is excitable, pugnacious, and aggressive toward mice living in the same fields. Their nests are a crude mass of dry grass fibers stripped from larger plant stems, placed in shallow surface depressions, among clumps of coarse grasses, underground in shallow tunnels, or under rocks or logs.
The species is very prolific and will breed throughout the year. Several litters may be produced annually, averaging 2 to 15 young per litter. The gestation period is 27 days, and the young are weaned in 10 to 15 days.
Most young breed for the first time at 2 to 3 months of age. Therefore, several generations may live in the same nest at one time. The average life span is 6 months.
Damage and Damage Identification
Cotton rat populations fluctuate greatly, ranging from 11 to 149 per acre (28 to 373/ha), and cause the most serious damage during population peaks. They may damage a variety of crops, including alfalfa, grains, grasses, vegetables, peanuts, fruit crops, sweet potatoes, and sugar beets. Cotton rats are especially troublesome in sugarcane and melons. Since these animals will eat quail eggs, a high cotton rat population may have a detrimental impact on quail nesting success. Cotton rats also compete with quail for the same foods.
Legal Status
Cotton rats are not protected in most states; some states classify them as non-game mammals. They may be taken if causing damage. Check local and state laws before beginning control measures.
Damage Prevention and Control Methods
Exclusion
Usually not practical.
Habitat Modification
Remove dense vegetation.
Repellents
None are registered.
Toxicants
2% zinc phosphide on dry bait.
Fumigants
None are registered.
Trapping
Snap traps (rat traps) or live traps.
Shooting
Not practical.
ACKNOWLEDGEMENTS
The above information was adapted from PREVENTION AND CONTROL OF WILDLIFE DAMAGE with permission of the editors, Scott E. Hygnstrom, Robert M. Timm, and Gary E. Larson (Cooperative Extension Division, Institute of Agriculture and Natural Resources University of Nebraska-Lincoln, United States Department of Agriculture Animal and Plant Health Inspection Service, Animal Damage Control, Great Plains Agricultural Council Wildlife Committee).
