Marsh rice rat
Oryzomys palustris
ITIS Species Code:   180336         NatureServ Element Code:   AMAFF01010
NatureServe Global Rank: 
NatureServe State (NC) Rank: 
Federal Status: 
NC State Status: 
Land Unit

US Fish & Wildlife Service
US Forest Service
US National Park Service
US Department of Defense
NC State Parks
NC University System
NC Wildlife Res. Com.
NC Forest Service
NC Div. of Coastal Mgmt.
Local Governments
Non-Governmental Org.
Other Public Lands
Private Lands

GAP Status 1-2
All Protected Lands




% of Dist. on
Prot. Lands

32.2 %
12.4 %
15.2 %
1.7 %
4.3 %
5.9 %
18.0 %
1.9 %
2.3 %
5.9 %
5.9 %
0.1 %
< 0.1 %

63.4 %
% of Dist. on
All Lands

6.2 %
2.4 %
3.1 %
0.3 %
0.8 %
1.1 %
3.5 %
0.4 %
0.4 %
< 0.1 %
1.1 %
< 0.1 %
80.6 %

12.2 %
These water-loving rodents are found in tidewater habitats along the Atlantic coast and in freshwater habitats inland to the lower Piedmont (Lee et al. 1982). Oryzomys palustris likes moist or watery habitats with a herbaceous cover of grasses or sedges (Whitaker and Hamilton 1998). It is semi-aquatic and prefers, but is not restricted to, locations near surface water (Golley 1962, Webster et al. 1985). Wet meadows and marshy areas are population strongholds for the species. But, it can be found in swamps, salt marshes, and in grassy areas and woodland clearings (Brown 1997, Whitaker and Hamilton 1998).


Prefers saltwater and freshwater marshes (semi-aquatic). May also be found in swamps and moist meadows. Able to move between adjacent islands by swimming across salt water; in Virginia, ten movements between two islands separated by 50 m and one movement between two islands separated by 300 m were documented (Forys and Dueser 1993, Forys and Moncrief 1994). Nests are placed in grassy vegetation under debris, or woven in aquatic emergents a foot or more above the high water line.

Occupied Landcover Map Units:
Code NameDescription NC Natural Heritage Program Equivalent
3 Tidal Marsh Fresh and brackish tidal marshes, including cord grass, wild rice, sawgrass and needlerush alliances. Brackish Marsh, Interdune pond, Maritime wet grassland
124 Maritime Scrubs and Tidal Shrublands Coastal shrubs including wax-myrtle, swamp rose, alder, yaupon, and greenbriar. Maritime Shrubs, Salt Shrub
371 Maritime Grasslands Dune grass community consisting of sea oats and beach grasses. Dune grass, Maritime dry grassland
75 Tidal Swamp Forest Swamp tupelo dominated forest with or without black tupelo and/or cypress trees. Restricted to the tidal zones in the coastal plain. May have inclusions of coastal red cedar woodlands. Tidal cypress - gum swamp
126 Interdune Wooded Depression Swamp Includes swamps dominated by sweetbay and swampbay or dogwood dominated forests. Maritime Shrub Swamp, Maritime Swamp Forest
380 Coastal Plain Fresh Water Emergent Emergent vegetation in fresh water seepage bogs, ponds and riverbeds of the coastal plain. Includes alliances dominated by sedges, eelgrass, as well as cane found in unforested cane-brakes. Small Depression Pond, Sandhill Seep, Floodplain Pool, Unforested Floodplain Canebrake, Riverscour Prairies, Vernal Pools
173 Coastal Plain Riverbank Shrubs Shrub dominated riverbanks, commonly dominated by willows and/or alders. Sand and Mud Bar
50 Coastal Plain Mixed Bottomland Forests Includes forests dominated by a variety of hardwood species, including sweetgum, cottonwood, red maple. Coastal Plain Bottomland Hardwood (in part), Coastal Plain Levee Forest
49 Coastal Plain Oak Bottomland Forest Bottomland forests dominated by deciduous oak alliances. Oaks represented can include swamp chestnut, cherrybark, willow, and/or overcup oak. Inclusions of loblolly pine temporarily flooded forests occur in patches. Hydrology is temporarily to seasonally flooded. Coastal Plain Bottomland Hardwoods (in part) blackwater subtype, brownwater subtype
158 Coastal Plain Nonriverine Wet Flat Forests Loblolly pine - Atlantic white-cedar - red maple - swamp tupelo saturated forests as well as forests dominated by loblolly, sweetgum, and red maple in non-riverine flats. Non-riverine Wet Hardwood Forest
41 Peatland Atlantic White-Cedar Forest Dense stands of Atlantic white cedar with saturated hydrology. Can include swamp tupelo, red maple, and pond pines with a moderate shrub and herb layer. Peatland Atlantic White-Cedar Forest
15 Seepage and Streamhead Swamps Includes extensive peat flats in the coastal plain, dominated by swamp tupelo, maples, and Atlantic white cedar alliances. In the sandhills includes streamhead pond pine and bay forests alliances. Saturated hydrology. Bay Forest, Small Depression Pocosin, Streamhead Atlantic White Cedar Forest, Streamhead Pocosins
30 Cypress-Gum Floodplain Forests Swamps dominated by black or swamp tupelo with or without Taxodium. Seasonally to semi-permanently flooded hydrology. Cypress-Gum Swamps
78 Pond-Cypress - Gum Swamps, Savannas and Lakeshores Cypress dominated swamps and lakeshores. Can include bays dominated by pond cypress or shorelines of coastal plain lakes with a narrow band of cypress. Non-riverine Swamp Forest, Natural Lakeshores (in part)
385 Oak Bottomland Forest and Swamp Forest The swamp chestnut oak, cherrybark oak, shumard oak and sweetgum alliance is one representative. Other alliances are dominated by water, willow, and overcup oaks. Swamp forests can be dominated by sweetgum, red maple, and black gum being dominant. Loblolly can occur in combination with sweetgum and red maple, or with tulip poplar. Includes saturated and semi- to permanently flooded forests in the mountains. Piedmont/Mountain Bottomland Forest, Piedmont/Mountain Swamp Forest
87 Pocosin Woodlands and Shrublands Includes pond pine woodland, low pocosin and high pocosin shrub dominated areas. Canebrakes and bay forests may be present. Pond Pine Woodlands, Peatland Canebrake, Small Depression Pocosin
67 Wet Longleaf or Slash Pine Savanna Wet flatwoods and pine savannas, typically dominated by longleaf pines, but slash or pond pines may be the dominant pines. Wet Pine Flatwoods
238 Piedmont/Mountain Submerged Aquatic Vegetation Seasonally to permanently flooded areas with aquatic vegetation. Waterlily, pondweed, hydrilla smartweed are a few of the species that can occur. Piedmont/Mountain Semipermanent Impoundment (in part)
239 Piedmont/Mountain Emergent Vegetation Emergent vegetation of all wetland hydrologies. Sites would commonly support species such as tussock sedge, rushs, and cattail alliances. Rocky Bar and Shore (in part)
267 Riverbank Shrublands Riverside shrubs with temporarily flooded hydrologies. Found in the both the Mountains and Piedmont. Containing dominants such as smooth alder and a Carolina or black willows. Sand and Mud Bar
269 Floodplain Wet Shrublands Saturated shrublands of the Piedmont, includes buttonbush, swamp-loosestrife, decodon and alders. Piedmont/mountain Semipermanent Impoundment
384 Piedmont/Mountain Mixed Bottomland Hardwood Forests Includes temporarily to seasonally forests dominated by hardwood species. Hardwoods include sweetgum, red maple, sycamore which co-occur in a mosaic of bottomland and levee positions. Includes alluvial hardwood forests in the mountains. Hemlock and white pine may occur as inclusions, but are generally mapped separately. Piedmont/Mountain Alluvial Forest, Piedmont/Mountain Levee Forest
180 Agricultural Crop Fields Farm fields used for row crops. No equivalent
205 Agricultural Pasture/Hay and Natural Herbaceous Farm fields used for pasture grass or hay production, as well as old fields dominated by native and exotic grasses. No equivalent
8 Open water Open water without aquatic vegetation. No equivalent
View Entire Landcover Legend
Additional Spatial Constraints:
Exclude all area outside of known range.
Exclude all land greater than 50 meters from an open water feature.
Exclude all land greater than 50 meters from wet vegetation.
Exclude all water greater than 50 meters from land.
Exclude salt water habitats.
Smith, A.T. and M.J. Vrieze. 1979. Population structure ofeverglade rodents:responses to a patchy environment. J. Mammalogy 60:778-794.

Wolfe, J.L. 1982. ORYZOMYS PALUSTRIS. Am. Soc. Mamm., Mammalian Species No. 176. 5 pp.

Edmonds, K. E., and M. H. Stetson. 1993. The rice rat ORYZOMYS PALUSTRIS in a Delaware salt marsh:annual reproductive cycle. Can. J. Zool. 71:1457-1460.

Forys, E. A., and R. D. Dueser. 1993. Inter-island movements of rice rats (Oryzomys palustris). Am. Midl. Nat. 130:408-412.

Goldman, E. A. 1918. The rice rats of North America (genus Oryzomys). North American Fauna 43:1-100.

Jones, J. K., Jr., et al. 1992. Revised checklist of North American mammals north of Mexico, 1991. Occas. Pap. Mus., Texas Tech Univ. (146):1-23.

Goodyear, N. C. 1992. Spatial overlap and dietary selection of native rice rats and exotic black rats. J. Mammalogy 73:186-200.

Forys, E. A., and N. D. Moncrief. 1994. Gene flow among island populations of marsh rice rats (ORYZOMYS PALUSTRIS). Virginia Journal of Science 45(1):1-11.

Wilson, D. E., and D. M. Reeder (editors). 1993. Mammal Species of the World:a Taxonomic and Geographic Reference. Second Edition. Smithsonian Institution Press, Washington, DC. xviii + 1206 pp.

Brown, L. N. 1997. A guide to the mammals of the southeastern United States. University of Tennessee Press, Knoxville. xiv + 236 pp.

Whitaker, J.O. Jr. and W.J. Hamilton, Jr. 1998. Mammals of the eastern United States. Cornell Univ. Press, Ithaca, New York. 583 pp.

Humphrey, S. R., and H. W. Setzer. 1989. Geographic variation and taxonomic revision of mink (MUSTELA VISON) in Florida. J. Mamm. 70:241-252.

Benson, D.L. & F.R. Gehlbach. 1979. Ecological and taxonomic notes on the rice rat (Oryzomys covesi) in Texas. J. Mamm. 60:225-228.

Lowery, G. H., Jr. 1974. The mammals of Louisiana and its adjacent waters. Louisiana State University Press, Baton Rouge. 565 pp.

Lee, D. S., L. B. Funderburg Jr., and M. K. Clark. 1982. A distributional survey of North Carolina mammals. Occasional Papers of the North Carolina Biological Survey, No. 1982-10. North Carolina State. Mus. Nat. Hist., Raleigh, North Carolina. 72 pp.

Negus, N.C., E. Gould, and R.K. Chapman. 1961. Ecology of the rice rat, Oryzomys palutris (Harlan) on Breton Island, Gulf of Mexico, with a critique on the social stress theory.Tulane Stud. Zool. 8:93-123.

Golley, F. B. 1962. Mammals of Georgia. University of Georgia Press, Atlanta, Georgia. 218 pp.

Birkenholz, D.E. 1963. Movement and displacement in the ricerat. Quarterly Journal Florida Academy of Science 26:269-274.

Davis, W. B. 1978. The mammals of Texas. Texas Parks and Wildlife Dept., Bull. No. 41. 294 pp.

Hamilton, William J., Jr., and John O. Whitaker, Jr. 1979. Mammals of the eastern United States. Cornell Univ. Press, Ithaca, New York. 346 pp.

Hall, E. R. 1981. The Mammals of North America. Second edition. 2 Volumes. John Wiley and Sons, New York, New York.

Honacki, J. H., K. E. Kinman, and J. W. Koepf (eds.). Mammal species of the world. Allen Press, Inc. and Assoc. Syst. Coll., Lawrence, Kansas. 694 pp.

Webster, W. D., J. F. Parnell and W. C. Biggs Jr. 1985. Mammals of the Carolinas, Virginia, and Maryland. The University of North Carolina Press, Chapel Hill, NC.

Jones, J. K., Jr., D. C. Carter, H. H. Genoways, R. S. Hoffman, D. W. Rice, and C. Jones. 1986. Revised checklistof North American mammals north of Mexico, 1986. Occas. Papers Mus., Texas Tech Univ., 107:1-22.

Goodyear, N. C. 1987. Distribution and habitat of the silver rice rat, ORYZOMYS ARGENTATUS. J. Mammalogy 68:692-695.

Caire, W., J. D. Tyler, B. P. Glass, and M. A. Mares. Z. Marsh (illustrator). 1989. Mammals of Oklahoma. University of Oklahoma Press, Norman. Oklahoma. 567 pp.

Goodyear, N. C. 1991. Taxonomic status of the silver rice rat, ORYZOMYS ARGENTATUS. J. Mamm. 72:723-730.

10 March 2005
This data was compiled and/or developed by the North Carolina GAP Analysis Project.

For more information please contact them at:
NC-GAP Analysis Project
Dept. of Zoology, NCSU
Campus Box 7617
Raleigh, NC 27695-7617
(919) 513-2853