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Range Map

Marsh Oryzomys

Marsh Oryzomys
Oryzomys palustris

This semi-aquatic rodent, also known as the "Marsh Rice Rat," is found across Tennessee.

: A small, slender rat that has course, moderately long grayish-brown fur, slightly streaked with black, and has a grayish-white or cream-colored belly and feet. The long, slender tail is sparsely haired and is brown above and white below. The eyes are relatively large and the well-haired ears stick out from the fur.
Length: 9.0 - 12.3 inches
Tail: 4.0 - 7.3 inches
Ears: 0.5 inches
Weight: 1.5 - 3.0 ounces

Similar Species:

  • Hispid Cotton Rat has a shorter tail and longer, more-grizzled fur.
  • Brown Rat is larger with proportionally shorter, thicker tail.
  • Eastern Woodrat is larger with a tail largely covered in hair and a white belly (sharp contrast with back).

: As its name indicates this rat is found primarily in marshes and wet open areas, but will use a variety of habitats.

Omnivorous; eats grasses, sedges, fruits, berries, fungi, nuts, and rice when available. Also, they will eat insects, snails, and bird eggs and young.

Breeding information:
Known to breed from February through November and possibly all year. Pregnancy lasts 25 days resulting in 1-7 (average 4-5) young per litter. They can produce as many as 5-6 litters per year. Females are frequently both pregnant and nursing young, and will mate as soon as a litter is born. Sizes of the litter depend upon the food and weather conditions. The young are weaned at 11 days and are expelled from the nest by the next week. They are fully grown at 4 months.

Status in Tennessee:
Not protected as this is a common species in marsh habitat.

Fun Facts
  • Marsh Oryzomys is an excellent swimmer and will dive underwater to escape danger.
  • These rodents will create "runways," which are slightly elevated platforms made of vegetation, to travel to and from feeding areas.

Best places to see in Tennessee: Edges of wetlands and marshes.

For more information:

Schwartz, C.W. and E.R. Schwartz. 2001. The Wild Mammals of Missouri, 2nd Edition. University of Missouri Press and Missouri Department of Conservation, Columbia, MO.