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Amazonian Marsh Rat

Holochilus sciureus

French: Oryzomys écureuil / German: Amazonas-Sumpfratte / Spanish: Rata de marisma del Amazonas

Taxonomy. Holochilus sciureus Wagner, 1842, “Rio Francisco [= Rio Sao Francisco] in Brasilien.” Regarded by P. Hershkovitz in 1955 to be in Minas Gerais State, Brazil. Holochilus sciureus is the type species of the genus. It was recently recognized as a species complex, with specimens from the central part of Brazil being considered as different species. Monotypic.

Distribution. Lowlands in the Guianas, E Peru, N & C Bolivia, and N, W & C Brazil.

Descriptive notes. Head—body 123-193 mm, tail 115-178 mm, hindfoot 35-46 mm. No specific data are available for body weight. See general characters of the genus under the Venezuelan Marsh Rat ( H. venezuelae) account. Dorsum of the Amazonian Marsh Rat is buffy or tawny, usually mixed with black; sides are paler; and venter is white to orange. Mystacial vibrissae are short and do not reach ear tips. Tail is unicolored and sparsely haired. Hindfeet have interdigital webbing. Skull is heavily built. Interorbital margins have moderately well-developed supraorbital crests. Incisors are opisthodont; molars are tetralophodont. Diploid complement of 2n = 55-56 (FN = 56).

Habitat. Grass-covered open areas, often swampy, and agricultural crops in the Amazon Basin and savannas of Guiana Shield.

Food and Feeding. The Amazonian Marsh Rat mainly eats stalks, leaves, seeds, and agricultural crops.

Breeding. The Amazonian Marsh Rat does not have reproductive peaks throughout the year. During drier periods, nests are built close to the ground, and during wetter conditions, nests are built higher. Nests sometimes consist of leaves and grass and are often close to water. Males generally reach sexual maturity c.2-3 months after weaning. Litters have 1-8 young, depending on environmental conditions.

Activity patterns. Observations of Amazonian Marsh Rats suggest nocturnal activity. They swim and climb very well and can stay in water for long periods.

Movements, Home range and Social organization. Amazonian Marsh Rats are frequently found in stomachs of other vertebrates and owl pellets.

Status and Conservation. Classified as Least Concern on The IUCN Red List.

Bibliography. Barreto & Garcia-Rangel (2005), Bates (1993), D'Elia, Hanson et al. (2015), Goncalves et al. (2015), Hershkovitz (1955), Twigg (1962, 1964).