11/6/2023 0 Comments Marsh rat boatOryzomys previously included many other species, which were reclassified in various studies culminating in contributions by Marcelo Weksler and coworkers in 2006 that removed more than 40 species from the genus. The marsh rice rat is classified as one of eight species in the genus Oryzomys, which is distributed from the eastern United States (marsh rice rat) into northwestern South America ( O. gorgasi). The species is not of conservation concern, but some populations are threatened. It is infected by many different parasites and harbors a hantavirus that also infects humans. Several animals prey on the marsh rice rat, including the barn owl, and it usually lives for less than a year in the wild. Newborns are helpless at birth, but are weaned after a few weeks. Litters of generally three to five young are born after a pregnancy around 25 days, mainly during the summer. Population densities are usually below 10 per ha (four per acre) and home ranges vary from 0.23 to 0.37 ha (0.57 to 0.91 acres), depending on sex and geography. Its diverse diet includes plants, fungi, and a variety of animals. The marsh rice rat is active during the night, makes nests of sedge and grass, and occasionally builds runways. One, Oryzomys couesi, occurs with the marsh rice rat in Tamaulipas and southern Texas. The species is part of the genus Oryzomys, which also includes several others occurring further south in Mexico, Central America, and northwestern South America, some of which have previously been regarded as subspecies of the marsh rice rat. Data from the mitochondrial cytochrome b gene indicate a deep divergence between populations east of Mississippi and those further west, which suggests that the western populations may be recognized as a separate species, Oryzomys texensis. The Florida Keys population is sometimes classified as a different species, the silver rice rat ( Oryzomys argentatus). Several subspecies have been described since the 1890s, mainly from Florida, but disagreement exists over their validity. John Bachman discovered the marsh rice rat in 1816, and it was formally described in 1837. The skull is large and flattened, and is short at the front. The feet show several specializations for life in the water. The upperparts are generally gray-brown, but are reddish in many Florida populations. Weighing about 40 to 80 g (1.4 to 2.8 oz), the marsh rice rat is a medium-sized rodent that resembles the common black and brown rat. It is found mostly in the eastern and southern United States, from New Jersey and Kansas south to Florida and northeasternmost Tamaulipas, Mexico its range previously extended further west and north, where it may have been a commensal in corn-cultivating communities. It usually occurs in wetland habitats, such as swamps and salt marshes. The marsh rice rat ( Oryzomys palustris) is a semiaquatic North American rodent in the family Cricetidae. ? Oryzomys argentatus Spitzer and Lazell, 1978.Oryzomys palustris sanibeli Hamilton, 1955.Oryzomys palustris planirostris Hamilton, 1955.Oryzomys natator floridanus Merriam, 1901.Oryzomys palustris coloratus Bangs, 1898.? Oryzomys palustris texensis J.A. Allen, 1894.Oryzomys palustris natator Chapman, 1893. ![]() A small part of the distribution of Oryzomys couesi is also shown (red). Current (blue) and approximate former (light blue) distribution of the marsh rice rat in the eastern United States.
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