Marsh Rice Rat

Marsh Rice Rat

Marsh oryzomys, Rice meadow-mouse, Rice-field mouse, Rice rat, Marsh mouse, Swamp rice rat

Kingdom
Phylum
Subphylum
Class
Order
Family
Subfamily
Genus
SPECIES
Oryzomys palustris
Population size
Unknown
Life Span
up to 1 yr
WEIGHT
40-80 g
LENGTH
226-305 mm

The Marsh rice rat is a medium-sized semiaquatic North American rodent that resembles the Common black and Brown rat. Its upper parts are generally gray-brown but are reddish in many Florida populations. The feet show several specializations for life in the water. It has small cheek pouches. The ears are about the same color as the upper parts, but a patch of light hairs is in front of them. The tail is dark brown above and may be paler below. The guard hairs are long and have unpigmented, silvery tips. When rice rats swim, the air is trapped in their fur, which increases buoyancy and reduces heat loss.

No

Nocturnal

He

Herbivore

Gr

Granivore

Gr

Graminivore

Ca

Carnivore

Sc

Scavenger

Se

Semiaquatic

Pr

Predator

Al

Altricial

Bu

Burrowing

Te

Terrestrial

Vi

Viviparous

So

Solitary

No

Not a migrant

M

starts with

Distribution

Geography

Marsh rice rats occur in much of the eastern and southern United States, northeast to southern New Jersey, and south to southeastern Texas and far northeastern Tamaulipas, Mexico. They live in several habitats, ranging from coastal salt marshes to mountain streams and clearings. They prefer areas where the ground is covered with grasses and sedges, which protect them from predators. Marsh rice rats also occur in drier uplands, which serve as sinks for young, dispersing animals and as refuges during high tide.

Marsh Rice Rat habitat map

Climate zones

Habits and Lifestyle

Marsh rice rats are semiaquatic, spending much of their time in the water. They are active during the night, so are rarely seen. They build nests of sedge and grass, about 13 cm (5 in) large, which are placed under debris, near shrubs, in short burrows, or high in aquatic vegetation. They may also use old nests of marsh wrens, red-winged blackbirds, and muskrats. Marsh rice rats sometimes make large runways or dig burrows. They are excellent swimmers, easily swimming more than 10 m (33 ft) under water, and often seek safety in the water when alarmed. They may occasionally climb in vegetation, but never higher than 90 cm (3.0 ft). Marsh rice rats are very clean and extensively groom themselves, perhaps to keep their fur water-repellent. They are solitary and territorial creatures that are aggressive towards conspecifics and emit high-pitched squeaks while fighting.

Seasonal behavior

Diet and Nutrition

Marsh rice rats are carnivores, herbivores, and scavengers. They take both vegetable and animal food. They eat mainly seeds and succulent parts of plants. Animal food includes insects, fiddler crabs, snails, fish, clams, and juvenile turtles. They scavenge on carcasses of muskrats, deermice, and sparrows, and may be the most important predator on eggs and young of the marsh wren. Rice rats also eat eggs and chicks of ground-nesting birds and may even prey on alligator eggs.

Mating Habits

REPRODUCTION SEASON
summer
PREGNANCY DURATION
25 days
BABY CARRYING
1-7 pups
FEMALE NAME
doe
MALE NAME
buck
BABY NAME
pup, pinkie, kit

Marsh rice rats breed mostly during the summer. After a gestation of about 25 days, females give birth to 3-5 young, although litter sizes may vary from 1 to 7. Females may have up to 6 litters a year. Newborns weigh 3 to 4 g (about 0.10 to 0.15 oz) and are blind and almost naked. The external ears (pinnae) soon unfold and on the first day, claws are visible and the young emit high-pitched squeaks. On the second day, they are able to crawl, and during the third to fifth days, the whiskers and eyelids develop. Between the 8th and 11th days, their eyes open, the fur develops, and the young begin to take solid food. Weaning occurs on the 11th to 20th day, and reproductive maturity is reached at about 50 to 60 days old.

Population

Population threats

The Marsh rice rat is a common, widespread, and stable species without major threats. However, the Florida Keys form is rare and in decline and is threatened by competition with the black rat, predation by domestic cats, habitat loss, and loss of genetic variation; in this area, the species is considered endangered. Changes in climate may also reduce the range of the Marsh rice rat in Texas, where it is now common, but may become threatened by habitat loss in the future.

Population number

The IUCN Red List and other sources don’t provide the number of the Marsh rice rat total population size. Currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are stable.

Fun Facts for Kids

  • The specific name of this rice rat is 'palustris' is Latin for 'marshy' and refers to the usual habitat of the species.
  • In dense vegetation, Marsh rice rats have a perceptual range less than 10 m (33 ft); this is the distance from which they can detect a patch of suitable habitat. When released outside of their natural wetland habitat, Marsh rice rats generally move either upwind or downwind, perhaps to move in a straight line, which is an efficient strategy to find suitable habitat.
  • The Marsh rice rat was a major pest on rice plantations as it was feeding on the rice when it was newly planted.

References

1. Marsh Rice Rat on Wikipedia - https://en.wikipedia.org/wiki/Marsh_rice_rat
2. Marsh Rice Rat on The IUCN Red List site - https://www.iucnredlist.org/species/42675/115200837

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