Missouri Department of Conservation
Missouri Department of Conservation

Taxonomy

Common Name: RAT, RICE

Phylum: CHORDATA

Class: MAMMALIA

Order: RODENTIA

Family: CRICETIDAE

Genus: ORYZOMYS

Species: PALUSTRIS

Taxonomic Authority: (HARLAN)

Taxonomy References: 018 , 002

Status

NONGAME
PEST/CROPS
GLOBAL RANK G5
STATE RANK SU

Status References: 001 , 006 , 011 , 013

Habitat Summary

"Occur in marshy areas with dense ground cover, grain fields and ditches with standing water and emergent herbaceous vegetation."

Primary Habitat: "Wetland matrix"

References: 001 , 004 , 005

Distribution

General Occurrence in State:

"Occurs in Mississippi lowlands *01*. May occur in southwest corner of state *02*."

County Occurance

County Occurence
Known Likely Unknown Not Likely Historic Extirpated
BOLLINGER BARRY BARTON ADAIR
CAPE GIRARDEAU BUTLER HOWELL ANDREW
DUNKLIN CARTER MISSISSIPPI ATCHISON
NEW MADRID IRON OREGON AUDRAIN
SCOTT JASPER OZARK BATES
STE. GENEVIEVE JEFFERSON RIPLEY BENTON
STODDARD MADISON SHANNON BOONE
WAYNE MCDONALD STONE BUCHANAN
NEWTON TANEY CALDWELL
PEMISCOT WASHINGTON CALLAWAY
PERRY CAMDEN
REYNOLDS CARROLL
ST. FRANCOIS CASS
CEDAR
CHARITON
CHRISTIAN
CLARK
CLAY
CLINTON
COLE
COOPER
CRAWFORD
DADE
DALLAS
DAVIESS
DEKALB
DENT
DOUGLAS
FRANKLIN
GASCONADE
GENTRY
GREENE
GRUNDY
HARRISON
HENRY
HICKORY
HOLT
HOWARD
JACKSON
JOHNSON
KNOX
LACLEDE
LAFAYETTE
LAWRENCE
LEWIS
LINCOLN
LINN
LIVINGSTON
MACON
MARIES
MARION
MERCER
MILLER
MONITEAU
MONROE
MONTGOMERY
MORGAN
NODAWAY
OSAGE
PETTIS
PHELPS
PIKE
PLATTE
POLK
PULASKI
PUTNAM
RALLS
RANDOLPH
RAY
SALINE
SCHUYLER
SCOTLAND
SHELBY
ST. CHARLES
ST. CLAIR
ST. LOUIS
SULLIVAN
TEXAS
VERNON
WARREN
WEBSTER
WORTH
WRIGHT

References for distribution: 001 , 002 , 017 , 014 , 003 , 016

Distribution by Watersheds

Miss. R. from St. Louis to River Aux Vases
Big R.
Miss. R. from River Aux Vases to Ohio R.
Castor R. and Castor R. Diversion Channel
Miss R. from Ohio R. to Arkansas Border
St. John's Ditch and Blue Ditch
St. Francis R. from Headwaters to Wappapello Dam
St. Francis R. from Wappapello Dam to Arkansas Border
Little R.
Black R.

Comments: "Likely to occur in units listed, based on county occurrence."

Distribution by Ecoregions

Mississippi River Alluvial Plains

Comments: ""

Distribution by Potential Natural Vegetation

Oak-Hickory Forest
Oak-Hickory-Pine Forest
Southern Floodplain Forest

Distribution by Natural Divisions of Missouri

Big Rivers: Lower Mississippi
Ozark Border: Mississippi River
Ozark: Springfield Plateau
Ozark: St. Francois Mountains
Ozark: Elk River
Ozark: White River
Ozark: Lower Ozark
Mississippi Lowlands
Mississippi Lowlands: Crowley's Ridge
Mississippi Lowlands: Lowlands

Habitat Associations

Species is associated with "Terrestrial" habitats.

National Wetlands Inventory Association:

Palustrine

Aquatic Associations:

"See Comments"
"Palustrine", "Emergent, persistent"
"Palustrine", "Forested"
"Palustrine", "Scrub/shrub, broad-leaved deciduous"

References for Aquatic Associations: 001 , 004 , 012

Habitat Types:

Swamp
Marsh
Cereal Grain
Perennial Grass (Warm season)
Perennial Grass (cool-season)
Shrub-Grass
Savanna (Grass-Shrub)
Legumes (Tame)

References for Habitat Types: 007 , 015

Terrestrial Natural Communities:

Savanna
Mesic Savanna
Wet-Mesic Savanna
Limestone/Dolomite Savanna
Chert Savanna
Sandstone Savanna
Sand Savanna
Igneous Savanna
Wetland
Marshes
Freshwater Marsh
Pond Marsh
Swamps
Swamp
Pond Swamp

References for Terrestrial Natural Communities: 001 , 004 , 005 , 007

Food Habits

Trophic Level:

"Omnivore"

Larval Food Habits

Comments for larval food habits:
""

References for larval food habits:

Juvenile Food Habits

Comments for Juvenile Food Habits:
""

References Juvenile Food Habits

Adult Food Habits

Shrubs; Fruit/Seeds
Dicotyledoneae (dicots); Fruit/Seeds
Forbs; All of plant
Eumycophyta (true Fungi); All of plant
Gramineae (grass); All of plant
Testudines (turtles); Juvenile stage
Reptiles; Not Specified
Carrion; Not Specified
Aquatic plants; Not Specified
Rice; Not Specified
Snails; Not Specified
Crustaceans; Not Specified
Malacostraca (lobster, shrimp, crayfish, crabs); Not Specified
Insects Insects; Not Specified

Comments for Adult Food Habits:
""

References Adult Food Habits 001 , 004 , 005 , 009

Niche Requirements

Egg Niche Requirements

References for egg niches requirements:

Feeding Larvae Niche Requirements

References for feeding larvae niche requirements:

Resting Larvae Niche Requirements

References for resting Larvae niche requirements:

Feeding Juvenile Niche Requirements

Inland wetlands: vegetated stream banks
Inland wetlands: swamp
Inland wetlands: marsh
General habitat association specified in comments(00270)
Edge: woodland/water edge
Edge: grassland/old field edge
Edge: grassland/water edge

References for feeding juvenile niche requirements: 001 , 004 , 005 , 009

Resting Juvenile Niche Requirements

Aquatic vegetation specified in comments(00120)
General habitat association specified in comments(00270)

References for resting juvenile niche requirements: 001 , 004 , 005 , 009

Breeding Adult Niche Requirements

Aquatic vegetation specified in comments(00120)
Inland wetlands: vegetated stream banks
Inland wetlands: swamp
Inland wetlands: marsh
General habitat association specified in comments(00270)
Edge: woodland/water edge
Edge: grassland/old field edge
Edge: grassland/water edge
Downed logs
Agricultural crops: small grains

References for feeding Adult niche requirements: 001 , 004 , 005 , 009 , 010

Feeding Adult Niche Requirements

Aquatic vegetation: cattail (Typha)
Aquatic vegetation: bulrush (Scirpus)
Aquatic vegetation: sedge (Carex)
Aquatic vegetation: spike rush (Eleocharis)
Aquatic vegetation: rushes (Juncus)
Aquatic vegetation specified in comments(00120)
Inland wetlands: vegetated stream banks
Inland wetlands: swamp
Inland wetlands: marsh
Inland wetlands: ditch
General habitat association specified in comments(00270)
Edge: woodland/water edge
Edge: grassland/old field edge
Edge: grassland/water edge
Agricultural crops: small grains
Agricultural crops: rice

References for feeding adult niche requirements: 001 , 004 , 005 , 009 , 012

Resting Adult Niche Requirements

Aquatic vegetation: cattail (Typha)
Aquatic vegetation: bulrush (Scirpus)
Aquatic vegetation: sedge (Carex)
Aquatic vegetation: spike rush (Eleocharis)
Aquatic vegetation: rushes (Juncus)
Aquatic vegetation specified in comments(00120)
Inland wetlands: vegetated stream banks
Inland wetlands: swamp
Inland wetlands: marsh
Inland wetlands: ditch
General habitat association specified in comments(00270)
Edge: woodland/water edge
Edge: grassland/old field edge
Edge: grassland/water edge
Agricultural crops: small grains
Agricultural crops: rice

References for resting adult niche requirements: 001 , 004 , 005 , 009 , 010

Niche Requirement Summary

Agricultural crops: rice
Agricultural crops: small grains
Aquatic vegetation specified in comments(00120)
Aquatic vegetation: bulrush (Scirpus)
Aquatic vegetation: cattail (Typha)
Aquatic vegetation: rushes (Juncus)
Aquatic vegetation: sedge (Carex)
Aquatic vegetation: spike rush (Eleocharis)
Downed logs
Edge: grassland/old field edge
Edge: grassland/water edge
Edge: woodland/water edge
General habitat association specified in comments(00270)
Inland wetlands: ditch
Inland wetlands: marsh
Inland wetlands: swamp
Inland wetlands: vegetated stream banks

Comments about Life History:

Code Comment
007 Breed February-November *01,04*, March-October *05*.
016 Nest diameter 12-18" *01*.
011 Don't often use underground burrow, may build nest in muskrat den *01*.
017 Gestation 25 days *01,04*.
018 Litter size 1-7, usually 4-5 for older females and 3 for young females *01,04*. 3-8 *05*.
019 Several litters per year, fewer litters if food supply or weather unfavorable, or if pop. Density too high *01,04*.
022 Mature at 7 weeks *01*. 6-8 weeks *04,05*.
034 Food, weather population density are limiting factors *01,04*.
035 Predators include owls, hawks, mink, weasels, raccoon, foxes, skunks, snakes *01,04,05*. Disease: typhus *01*.
099 Young weaned at 11 days *01*. Build runways in vegetation, may build feeding platforms in marshy areas *01,04*. Males and females may share nest in winter *01*. May destroy crops or pastures *01,04*. Are an important food source for many predators *01,04*.

Life History Information

Periodicity: active at night
Limiting factors specified in comments(034)
Regulatory factors specified in comments(035)
Other life history information specified in comments(099)
Origin in state: native
Seasonal distribution in state: all seasons
Foraging strategy: gleaning
Foraging strategy: grazing
Foraging sites: ground
Breeding season specified in comments(007)
Nest/den site: on the ground
Nest/den site: underground burrow
Nest/den site: floating aquatic vegetation
Nest/den site: log
Nest/den site specified in comments(011)
Nest materials: grasses
Nest materials: leaves
Nest dimensions specified in comments(016)
Gestation/incubation period specified in comments(017)
Clutch/litter size specified in comments(018)
Number of broods/litters per year specified in comments(019)
Development of young at birth/hatching: altricial
Parental care of young: female
Age at sexual maturity specified in comments(022)

Comments about Life History:

Code Comment
007 Breed February-November *01,04*, March-October *05*.
016 Nest diameter 12-18" *01*.
011 Don't often use underground burrow, may build nest in muskrat den *01*.
017 Gestation 25 days *01,04*.
018 Litter size 1-7, usually 4-5 for older females and 3 for young females *01,04*. 3-8 *05*.
019 Several litters per year, fewer litters if food supply or weather unfavorable, or if pop. Density too high *01,04*.
022 Mature at 7 weeks *01*. 6-8 weeks *04,05*.
034 Food, weather population density are limiting factors *01,04*.
035 Predators include owls, hawks, mink, weasels, raccoon, foxes, skunks, snakes *01,04,05*. Disease: typhus *01*.
099 Young weaned at 11 days *01*. Build runways in vegetation, may build feeding platforms in marshy areas *01,04*. Males and females may share nest in winter *01*. May destroy crops or pastures *01,04*. Are an important food source for many predators *01,04*.

References for life history: 001

Management

Beneficial Management Practices:

Water - develop/maintain wetlands
Water - develop/maintain freshwater marsh
Water - develop/maintain streamside vegetation
Agricultural - develop and maintain food plots
Agricultural - develop and maintain water holes, ponds, potholes, etc.
Agricultural - maintain riparian habitats
Agricultural - control grazing by domestic livestock
Agricultural - develop/maintain edge (ecotones)
Agricultural - maintain streamside vegetation
Agricultural - retention of crop residue over winter
Agricultural - no-till farming
Agricultural - develop/maintain ditchbank vegetation
Forest - develop and maintain food plots
Forest - maintain riparian habitats
Forest - maintain streamside vegetation
Grassland - develop and maintain water holes, ponds, potholes, etc.
Grassland - maintain riparian habitats
Grassland - control grazing of domestic livestock
Grassland - develop/maintain edge (ecotones)
Grassland - maintain streamside vegetation

Beneficial Management References: 001 , 004 , 005 , 009

Adverse Managment Practices:

Water - application of herbicides
Water - dredging and filling
Water - control aquatic plants
Water - burning marshes or wetlands
Water - drainage of wetlands, marshes, ponds, lakes
Agricultural - application of herbicides
Agricultural - uncontrolled grazing by domestic livestock
Agricultural - prescribed/controlled burning
Agricultural - haying/mowing
Grassland - application of herbicides
Grassland - uncontrolled grazing of domestic livestock
Grassland - prescribed/controlled burning
Grassland - haying/mowing

Adverse Management References: 001 , 004 , 005 , 009

Comments on Management:

References for Management Comments:

References

Reference Code Citation
001 Schwartz, C.W. and E.R. Schwartz. 1981. The Wild Mammals Of Missouri 2nd Ed. Univ. Of Missouri Press And Mo Dept. Of Conservation, Columbia, Mo. 356 Pp.
002 Hall, E.R. 1981. The Mammals Of North America, 2nd Ed. John Wiley And Sons, Inc. New York. 1181pp.
003 Unpb Elder, W.H. Collection Records. 112 Stephens Hall, Univ. Of Mo, Columbia, Mo 65211. 573-8
004 Sealander, J.A. 1979. A Guide To Arkansas Mammals. River Road Press, Conway, Arkansas. 313 Pp.
005 Hoffmeister, D.F. and C.O. Mohr. 1972. Fieldbook Of Illinois Mammals Dover Publ., Inc., New York. 233 Pp.
006 The Wildlife Code of Missouri. Missouri Department of Conservation, P.O. Box 180, Jefferson City, MO 65102. 573-751-4115.
007 Kelly, G. (Ed.) 1986. Animal Habitat Relations Handbook. Mo Dept. Of Conservation and U.S.D.A. Forest Service. Jefferson City, Mo. 293 Pp.
008 Thom, R.H. and J.H. Wilson. 1980 The Natural Divisions Of Missouri. Trans. Mo Acad. Sci. 14:9-24.
009 Hamilton, W.J.,Jr. 1966. Habits Of The Swamp Rice Rat, Oryzomys Palustris Palustris (Harlan). Amer. Midl. Nat. 36:730-736.
010 Unpb Clawson, R. Mo Dept. Of Conservation, 1110 S. College Ave., Columbia, Mo 65201. (573-882-9880).
011 The Checklist Of Rare And Endangered Species Of Missouri. 44 Pp.
012 Hofmann, J.E., J.E. Gardner and M.J. Morris. 1990. Distribution, Abundance And Habitat Of The Marsh Rice Rat (Oryzomys Palustris) In Southern Illinois. Trans. Il. Acad. Sci. 83:162-180.
013 Missouri Natural Heritage Program. 2004. Missouri Species and Communities of Conservation Concern Checklist. Missouri Department Of Conservation. Jefferson City, Missouri. 47 Pp.
014 Unpb Mccarty, K. 1997 Collector's Permit Report. Missouri Dept. Of Conservation, P.O. Box 180, Jefferson City, Mo 65102. 573-751-4115.
015 Cooper, J.L. 1997. A Comparison Of Avian And Small Mammal Populations In Three Open-Land Habitats At Land Between The Lakes, Tennessee And Kentucky. Twra Tech. Rept. 97-12. 136 Pp.
016 Unpb Big Oak Tree State Park. Mammal Checklist. 13640 South Hwy. 102, East Prairie, MO 63845, 573-649-3149.
017 UNPB Shelby Timm. MDC Mammal Database. Missouri Dept. of Conservation, Ellington Office. 2929 County Rd 618, Ellington, MO 63638/
018 The Mammal Diversity Database of the American Society of Mammalogists. 02/22/2023. https://www.mammaldiversity.org/index.html