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									Donald W. Hawthorne
Associate Deputy Administrator
USDA-APHIS-
                                                  COTTON RATS
Animal Damage Control
Washington, DC 20090




Fig. 1. Hispid cotton rat, Sigmodon hispidus




                                                  Fumigants
                                                                                                Identification
Damage Prevention and
                                                                                                The hispid cotton rat (Sigmodon
Control Methods                                   Not practical.
                                                                                                hispidus) is a moderately large, robust
Exclusion                                         Trapping                                      rodent with a scaly, sparsely haired
                                                  Snap traps (rat traps).                       tail that is shorter than the combined
Usually not practical.
                                                                                                head and body.
Cultural Methods                                  Live traps.
                                                                                                Cotton rats have relatively large eyes.
Remove dense vegetation.                          Shooting                                      The ears are large but almost hidden in
Repellents                                        Not practical.                                the fur. They have four toes and a
                                                                                                small thumb on their front feet and
Not effective.                                                                                  five toes on each hind foot. The cotton
Toxicants                                                                                       rat has very small internal cheek
                                                                                                pouches. Distinguishing characteristics
2% zinc phosphide on dry bait.                                                                  are the rough grizzled appearance of
                                                                                                the blackish or grayish fur and the
                                                                                                rather stiff black guard hairs.




                                               PREVENTION AND CONTROL OF WILDLIFE DAMAGE — 1994
                                               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
                                                                                                                                          B-97
                                               Great Plains Agricultural Council
                                               Wildlife Committee
       This rodent has a high “Roman” nose               New Mexico. They are very similar to        Most young breed for the first time at
       and color similar to that of a javelina,          the hispid cotton rat.                      2 to 3 months of age. Therefore, sev-
       resulting in the name “javelina rat” in                                                       eral generations may live in the same
       many areas.                                                                                   nest at one time. The average life span
                                                         Habitat                                     is 6 months.
       The total length averages 10 inches (25
       cm) including the tail length of 4                Cotton rats prefer dense cover such as
       inches (10 cm). The cotton rat may be             grassy fields, overgrown roadsides, or      Damage
       distinguished from the Norway rat by              fencerow vegetation adjacent to culti-
       its smaller size, shorter tail, and longer        vated fields. They also occupy mead-        Cotton rat populations fluctuate
       grizzled fur. Evidence of cotton rat              ows, marshy areas, cactus patches, and      greatly, ranging from 11 to 149 per
       presence are stem and grass cuttings              weedy ditch banks. Under the protec-        acre (28 to 373/ha), and cause the most
       2 or 3 inches (5 or 8 cm) in length piled         tive cover, the cotton rat will have        serious damage during population
       at various locations along runways,               well-defined runways radiating in all       peaks. They may damage a variety of
       which are 3 to 5 inches (8 to 13 cm)              directions from the nest site.              crops, including alfalfa, grains, grasses,
       wide. Pale greenish or yellow drop-                                                           vegetables, peanuts, fruit crops, sweet
       pings, about 3/8 inch (9 mm) in length                                                        potatoes, and sugar beets. Cotton rats
       and 3/16 inch (5 mm) in diameter,                 Food Habits                                 are especially troublesome in sugar-
       may also be present along the run-                                                            cane and melons. Since these animals
       ways.                                             Cotton rats are normally herbivores,
                                                         eating the roots, stems, leaves, and        will eat quail eggs, a high cotton rat
                                                         seeds of a wide variety of plants. They     population may have a detrimental
                                                         also feed on sugarcane, fruits, berries,    impact on quail nesting success.
                                                         and nuts. Cotton rats will cut tall         Cotton rats also compete with quail for
                                                         plants off at the base and continue to      the same foods.
                                                         cut them into shorter sections. They
                                                         also eat insects, the eggs and young of     Legal Status
                                                         ground-nesting birds (particularly
                                                         quail), and the carcasses of dead           Cotton rats are not protected in most
                                                         animals.                                    states; some states classify them as
                                                                                                     nongame mammals. They may be
                                                         General Biology,                            taken if causing damage. Check local
                                                                                                     and state laws before beginning con-
                                                         Reproduction, and                           trol measures.
                                                         Behavior
                                                                                                     Damage Prevention and
                                                         Cotton rats are basically nocturnal but
       Fig. 2. Range of the hispid cotton rat in North   will venture out in the daytime and are     Control Methods
       America.                                          active year-round. The home range is
                                                         small — from 1/4 to 3/4 acre (0.1 to        Exclusion
                                                         0.3 ha) for females and 1 to 1 1/4 acres    If the area is small or the crop to be
       Range
                                                         (0.4 to 0.5 ha) for males. Cotton rats do   protected is of high value, a sheet-
       The hispid cotton rat occurs over most            not store food or hibernate. They can       metal barrier 18 inches (46 cm) tall
       of the southern United States, from the           swim and do not hesitate to do so.          may be used to exclude cotton rats.
       southeastern tip of California, southern          This species is excitable, pugnacious,      Bury the barrier about 6 inches (15 cm)
       Arizona and New Mexico, north to                  and aggressive toward mice living in        to prevent cotton rats from burrowing
       eastern Colorado, eastward through                the same fields. Their nests are a crude    under it.
       the southern portions of Kansas and               mass of dry grass fibers stripped from
       Missouri, through Tennessee and                   larger plant stems, placed in shallow       Cultural Methods
       North Carolina, and southward along               surface depressions, among clumps of
       the Atlantic coast through Florida, the           coarse grasses, underground in shal-        Remove dense cover by burning,
       Gulf states, and up the Rio Grande                low tunnels, or under rocks or logs.        mowing, plowing, or the use of herbi-
       Valley (Fig. 2).                                                                              cides to reduce habitat and prevent
                                                         The species is very prolific and will       large population increases. Habitat
       Two other species of cotton rat, the              breed throughout the year. Several lit-     modification is best as a preventive
       least cotton rat (S. minimus) and the             ters may be produced annually, aver-        measure, since this control method
       yellownose cotton rat (S. ochrognathus),          aging 2 to 15 young per litter. The         will have little effect on the ensuing
       occur only in small areas of south-               gestation period is 27 days, and the        damage once a population reaches its
       eastern Arizona and southwestern                  young are weaned in 10 to 15 days.          peak.

B-98
Repellents                                  Trapping                                   Acknowledgments
None are registered for repelling cot-      Small rodent live traps or rat-sized       Figures 1 and 2 from Schwartz and Schwartz
ton rats.                                   snap traps are effective for catching a    (1981), adapted by Jill Sack Johnson.
                                            small number of animals. The traps
Toxicants                                   should be baited with a mixture of         For Additional
                                            peanut butter and oatmeal or a piece
Only zinc phosphide (2% active ingre-
                                            of fresh carrot or sweet potato. The
                                                                                       Information
dient) is currently registered and being
                                            trap should be set in the runway at a      Camedon, G. N., and S. R. Spencer. 1981.
marketed for cotton rat control, and its                                                 Sigmodon hispidus. Mammal. Sp. 158:1-9.
                                            right angle to the direction of travel.
use is limited to sugarcane fields.
                                                                                       Clark, D. O. 1972. The extending of cotton rat
When applying toxic bait, lightly
                                                                                          range in California — their life history and
scatter teaspoon quantities in the rats’    Economics of Damage                           control. Proc. Vertebr. Pest Conf. 5:7-14.
runways at 12- to 30-foot (3.6- to 9-m)
intervals according to label instruc-
                                            and Control                                Clark, J. P. 1986. Vertebrate pest control hand-
                                                                                          book. California Dept. Food Agric. Sacra-
tions.                                                                                    mento. 615 pp.
                                            The amount and extent of damage is
Fumigants
                                            directly related to the relative density
                                            of the cotton rat population. The cost
Fumigants are not very practical            of control must be weighed against the
because cotton rats use their burrows                                                  Editors
                                            value of the crop to be protected, such
                                                                                         Scott E. Hygnstrom
and tunnels infrequently. Since state       as sugarcane or melons.                      Robert M. Timm
pesticide registrations vary, check with                                                 Gary E. Larson
the local extension office or state wild-
life agency for information on repel-
lents, toxicants, and fumigants in your
area.




                                                                                                                                          B-99
B-100

								
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