Amazonian marsh rats are smaller than the common brown rat, but otherwise have a similar appearance. They range from in head-body length, with a tail long, and typically weigh between. They have short fur, which is tawny or buff over the back, becomes paler on the flanks, and fades to white or pale orange on the underparts. The hindfeet are noticeably larger than the forepaws, with prominent claws and partial webbing between the toes. There is also a slight fringe of longer, silvery, hair, around the soles of the feet. Females have eight or ten teats.
Distribution and habitat
Amazonian marsh rats are found across much of northern South America east of the Andes. They inhabit open areas such as grasslands, savanna, marshes, clearings in the rainforest, and farmland, at elevations up to. Although the exact taxonomic status of some populations is unclear, two subspecies are currently recognised:
Amazonian marsh rats feed primarily on grass stems, although they also eat some seeds, and small quantities of sedges, other plants, and even small invertebrates. They are nocturnal, occupying a home range of as little as. Females construct spherical nests made of leaves in order to rear their young. These nests may be on the ground in dense vegetation or cracks in the earth, but are more commonly located above the ground, attached to sturdy stems such as those of sugar cane or rice plants. The inner lining of the nest consists of finely shredded leaves, with a more intact outer shell. Predators include caimans, rattlesnakes, barn owls, hawks, kites, and probably crab-eating foxes. They breed throughout the year, although the fertility of both sexes increases during periods of high rainfall. Courtship lasts around 4 days before mating occurs, and gestation lasts 29 days. The female gives birth at night or at dawn to a litter of up to eight blind, hairless, pups, each measuring around and weighing. The fur begins to appear after five days, and the first teeth emerge at ten days. The young are weaned a fifteen days, by which time their eyes have opened. The rats reach sexual maturity at three to four months, with females maturing more slowly than males.
