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Smithsonian National Museum of Natural History, North American Mammals

  Rodentia · Cricetidae · Oryzomys palustris

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Oryzomys palustris

Marsh Rice Rat

Order: Rodentia
Family: Cricetidae

Image of Oryzomys palustris
Orysomys palustris - lower image is silvery subspecies O. p. argentatus of Florida Keys
Click to enlarge this image. (78 kb)

Conservation Status: Least Concern.

Marsh rice rats are among the most common mammals inhabiting tidal marshes of the Gulf and Atlantic coasts. Being good swimmers, diving to 10 m and crossing 300 m stretches of water, and able climbers, these rice rats are suitably equipped for life in an environment where water levels fluctuate. They and Coues's rice rats are carnivores: they prey on crabs, clams, snails, fish, insects, baby turtles, and birds. As opportunistic feeders, they will also eat carrion and even some plant material. In some places, they breed throughout the year, and in other places, they breed from March to October. A litter of five, after a gestation of about 25 days, is typical. In a little over a week, the newborn rats' eyes open and they are beginning to nibble solid food. They are weaned before they are three weeks old. As with many nocturnal rodents, owls are the main predator.

Also known as:

Rice Rat

Sexual Dimorphism:

Males are larger than females.


Average: 226 mm males; 217 mm females
Range: 193-262 mm males; 191-253 mm females


Average: 56 g males; 48 g females
Range: 46-80 g males; 40-60 g females


Harlan, R., 1837.  Description of a new species of quadruped, of the Order Rodentia, inhabiting the United States; by R. Harlan, M.D. Mus palustris, p. 385.  American Journal of Science, 31:385-386.


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Distribution of Oryzomys palustris

Image of Oryzomys palustris
Click to enlarge this image. (135kb)

Skull of Oryzomys palustris
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