Oryzomys palustris 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Rodentia Cricetidae

Scientific Name: Oryzomys palustris (Harlan, 1837)
Common Name(s):
English Marsh Rice Rat
Spanish Un Ratón Arrozalero
Taxonomic Notes: Analysis of cranial variation in Oryzomys by Humphrey and Setzer (1989) indicated that O. argentatus should be included in this species. Goodyear (1991) reinstated O. argentatus as a species, but this was not followed by Baker et al. (2003), and Musser and Carleton (in Wilson and Reeder 1993, 2005) cited the more thorough study by Humphrey and Setzer (1979) in not accepting argentatus as a species (though they did state that the status of argentatus merits further study using genetic techniques).

Oryzomys palustris and O. couesi formerly were considered to be conspecific (Hall 1981); they were regarded as separate species by Honacki et al. (1982), Jones et al. (1986, 1992), and Musser and Carleton (in Wilson and Reeder 1993, 2005), following Benson and Gehlbach (1979). An electrophoretic study by Schmidt and Engstrom (1994) also concluded that O. palustris and O. couesi are distinct species. The taxonomic scope of the genus Oryzomys is unsettled, as are the taxonomic limits of some of the species included in the genus Oryzomys (Musser and Carleton, in Wilson and Reeder 1993, 2005).

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2016
Date Assessed: 2016-08-09
Assessor(s): Cassola, F.
Reviewer(s): Amori, G.
Contributor(s): Hammerson, G.A. & Linzey, A.
Listed as Least Concern because it is very widespread, and common in suitable habitat throughout most of its range, its populations are stable and there are no major threats.
Previously published Red List assessments:

Geographic Range [top]

Range Description:This species occurs from eastern Texas to southeastern Kansas, east to southern New Jersey/Delaware and Florida (Honacki et al. 1982). The previously recognized species O. argentatus, is now included in O. palustris, and is known to occur on nine islands in the lower Florida Keys and probably occurs on several others (Goodyear 1992).
Countries occurrence:
United States (Alabama, Arkansas, Delaware, Florida, Georgia, Illinois, Kansas, Kentucky, Louisiana, Maryland, Mississippi, Missouri, New Jersey, North Carolina, Oklahoma, Pennsylvania - Regionally Extinct, South Carolina, Tennessee, Texas, Virginia)
Additional data:
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:This species is considered secure in its range (NatureServe). Reported densities range from about 4/ha in a Texas coastal prairie to >50/ha in the Florida Everglades.
Current Population Trend:Stable
Additional data:
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:It prefers saltwater and freshwater marshes (semi-aquatic). It may also be found in swamps and moist meadows. Uplands bordering wetlands may be important as refuges during high tides (Kruchek 2004). 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). Nests are placed in grassy vegetation under debris, or woven in aquatic emergents a foot or more above the high water line.

Breeding may occur throughout the year, particularly early spring. Gestation lasts 21-28 days. Litter size is 4-6 (range 1-7). Several litters per year, up to six are known. Young are weaned within two weeks.

The average home range is one acre (Negus et al. 1961). This species is an effective disperser over water and a good colonizer of barrier islands (Loxterman et al. 1998). Diet includes rice and seeds of herbaceous plants. When available (in season), arthropods make up 75% of the diet (Negus et al. 1961). It is primarily nocturnal.
Systems:Terrestrial; Freshwater
Generation Length (years):0-1

Threats [top]

Major Threat(s): There are no major threats to this species.

Conservation Actions [top]

Conservation Actions: This species occurs in several protected areas throughout its range. The subspecies in the Florida keys may be of conservation concern.

Errata [top]

Errata reason: This errata assessment has been created because the map was accidentally left out of the version published previously.

Classifications [top]

4. Grassland -> 4.4. Grassland - Temperate
4. Grassland -> 4.6. Grassland - Subtropical/Tropical Seasonally Wet/Flooded
5. Wetlands (inland) -> 5.3. Wetlands (inland) - Shrub Dominated Wetlands
5. Wetlands (inland) -> 5.4. Wetlands (inland) - Bogs, Marshes, Swamps, Fens, Peatlands
12. Marine Intertidal -> 12.5. Marine Intertidal - Salt Marshes (Emergent Grasses)
14. Artificial/Terrestrial -> 14.1. Artificial/Terrestrial - Arable Land

In-Place Research, Monitoring and Planning
In-Place Land/Water Protection and Management
  Conservation sites identified:Yes, over entire range
In-Place Species Management
In-Place Education

Bibliography [top]

Baker, R.J., Bradley, L.C., Bradley, R.D., Dragoo, J.W., Engstrom, M.D., Hoffman, R.S., Jones, C.A., Reid, F., Rice, D.W. and Jones, C. 2003. Revised checklist of North American mammals north of Mexico, 2003. Occasional Papers, Museum of Texas Tech University 229: 23 pp.

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

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

Goodyear, N. C. 1991. Taxonomic status of the silver rice rat, Oryzomys argentatus. Journal of Mammalogy 72: 723-730.

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

Hafner, D.J., Yensen, E. and Kirkland, G.L., Jr. 1998. Status survey and conservation action plan - North American Rodents. IUCN/SSC Rodent Specialist Group, Gland, Switzerland.

Hall, E.R. 1981. The Mammals of North America. John Wiley and Sons, New York, USA.

Honacki, J.H., Kinman, K.E. and Koeppl, J.W. 1982. Mammal species of the world: A taxonomic and geographic reference. Allen Press.

Humphrey, S. R. and Setzer, H. W. 1989. Geographic variation and taxonomic revision of mink (Mustela vison) in Florida. Journal of Mammology 70(2): 241-252.

IUCN. 2016. The IUCN Red List of Threatened Species. Version 2016-3. Available at: (Accessed: 07 December 2016).

IUCN. 2017. The IUCN Red List of Threatened Species. Version 2017-1. Available at: (Accessed: 27 April 2017).

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

Jones Jr., J.K., Hoffman, R.S., Rice, D.W., Jones, C., Baker, R.J. and Engstrom, M.D. 1992. Revised checklist of North American mammals north of Mexico, 1991. Occasional Papers, Museum of Texas Tech University 146: 1-23.

Kruchek, B. L. 2004. Use of tidal marsh and upland habitats by the marsh rice rat (Oryzomys palustris). Journal of Mammalogy 85: 569-575.

Loxterman, J. L., Moncrief, N. D., Dueser, R. D., Carlson, C. R. and Pagels, J. F. 1998. Dispersal abilities and genetic population structure of insular and mainland Oryzomys palustris and Peromyscus leucopus. Journal of Mammalogy 79: 66-77.

Musser, G.G. and Carleton, M.D. 1993. Family Muridae. In: D.E. Wilson and D.A. Reeder (eds), Mammal species of the world: A taxonomic and geographic reference, pp. 501-736. Smithsonian Institution Press, Washington, DC, USA.

Musser, G.G. and Carleton, M.D. 2005. Superfamily Muroidea. In: D.E. Wilson and D.A. Reeder (eds), Mammal Species of the World: a geographic and taxonomic reference, pp. 894-1531. The John Hopkins University Press, Baltimore, USA.

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

Pacifici, M., Santini, L., Di Marco, M., Baisero, D., Francucci, L., Grottolo Marasini, G., Visconti, P. and Rondinini, C. 2013. Generation length for mammals. Nature Conservation 5: 87–94.

Schmidt, C. A. and Engstrom, M. D. 1994. Genic variation and systematics of rice rats (Oryzomys palustris species group) in southern Texas and northeastern Tamaulipas, Mexico. Journal of Mammalogy 75: 914-928.

Wilson, D.E. and Ruff, S. 1999. The Smithsonian Book of North American Mammals. Smithsonian Institution Press, Washington, DC, USA.

Wolfe, J. L. 1982. Oryzomys palustris. Mammalian Species 176: 1-5.

Citation: Cassola, F. 2016. Oryzomys palustris (errata version published in 2017). The IUCN Red List of Threatened Species 2016: e.T42675A115200837. . Downloaded on 21 April 2018.
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