BEHAVIOR: Marsh rice rats are mainly nocturnal and semiaquatic. They make numerous runways in the grass for travel through their marshy environment, but are also great swimmers. They can dive and swim underwater to escape predators.

REPRODUCTION: Marsh rice rats usually breed throughout the year. The gestation period lasts about 25 days, and the litter sizes are about 3-4. Several litters can be produced in a year. Weaning occurs at approximately 10 days, and the young become sexually mature in about 2 months. They then breed during their first summer.