Marsh Rice Rat

Scientific Name
Oryzomys palustris
Also Known As
Florida Marsh Mouse, Rice Meadow-mouse
All of Florida
Crabs, Snails, Cordgrass
Life Expectancy
1 Year
A Florida Marsh Rice Rat on a log

Photo 33486865 (c) lrbobay, CC BY-NC

Rount-tailed muskrat conservation status - endangered

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Round-tailed Muskrat (Florida Water Rat) in Central Florida

The marsh rice rat (Oryzomys palustris) is a semi-aquatic rodent species found throughout wetlands in central Florida.

Often confused with roof rats and Norway rats, rice rats can be identified by their smaller size, brownish-gray fur, white underside, and partially webbed hindfeet. This guide covers rice rat identification, biology, health risks, signs of infestation, and prevention and control in central Florida homes and properties.

Appearance and Identification

Rice rats can be distinguished from Rattus rats and house mice by the following physical characteristics

Adult Marsh Rice Rat

Photo 103883206 (c) jpollpeter, CC BY-NC  modified

Adult Marsh Rice Rat

  • Size: Adults reach 6-9 inches (15-23 cm) long including the tail and weigh 1.5-3 ounces (40-80 grams).
  • Tail: The tail is longer than the head and body combined at 3.5-5 inches (9-13 cm) in adults. It is scaly with short hairs.
  • Fur: Adults are brownish-gray above and pale gray/white below. The fur is soft and dense.
  • Head: Blunt rostrum, small eyes and ears.
  • Feet: Partially webbed hindfeet adapted for swimming. Smaller forefeet.
A Juvenile Marsh Rice Rat caught

Photo 24473626 (c) Yianni Laskaris, CC BY-NC

Juvenile Marsh Rice Rat

  • Size: Newborns are about 2 inches (5 cm) long and weigh 0.5 ounces (15 grams). They reach 5-6 inches (13-15 cm) long including the tail by 4-5 weeks old.
  • Fur: Juvenile fur is grayish-brown and finely textured as they grow.
  • Features: Younger rice rats have a rounded, furry appearance with small ears, feet, and tail. Their rostrum is blunt.

Rice rats are smaller and lighter in color compared to Rattus rats. They have smaller ears, shorter tails, and partially webbed hind feet unlike house mice. Careful inspection of tracks, tail scales, and droppings aids identification.

Maturation Rate

Young marsh rice rats grow quickly after birth. They open their eyes by 2 weeks old. By 3-4 weeks old, juveniles are weaned from maternal care and leave the nest. Rice rats reach adult size by 2 months of age. Their rapid maturation allows populations to rebound quickly after control efforts.

Habits and Behavior

Marsh Rice rats are active year-round in central Florida, often during the day and around dusk. They prefer wet, marshy areas and constructed burrows in grassy fields. Marsh Rice rats are good swimmers and climbers but stay mostly on the ground.

Outdoors, rice rats build spherical nests of grasses inside burrows or natural cavities. Indoors, they nest in dark, humid areas like attics and wall voids. Rice rats occasionally invade homes but prefer to remain near water sources. They are not very social and mostly solitary.

Reproduction and Lifespan

Marsh Rice Rats can breed year-round in central Florida. Females produce 2-4 litters annually with 2-7 young per litter. The gestation period is 27-30 days. Rice rats become reproductively mature by 60 days old. Their average lifespan is about 1 year in the wild.