Distribution and Ecology
As far as known, Oryzomys gorgasi has a disjunct distribution in northwestern South America, including Colombia, Venezuela, and Curaçao. In a 2009 paper, Carleton and Arroyo-Cabrales speculated that its distribution may extend into Central America. The Colombian population is known from the holotype only, caught at Loma Teguerre (7°54'N, 77°W) in Antioquia Department, northwestern Colombia, near the Río Atrato, at about 1 m above sea level. The location is apparently a freshwater swamp, and Hershkovitz suggested that O. gorgasi probably occurred throughout the swamp forests in the Río Atrato basin. On Curaçao, it is known from cave faunas at Tafelberg Santa Barbara, Noordkant, Ser'i Kura, and Hermanus. At Tafelberg Santa Barbara, it was found in association with introduced black rats (Rattus rattus), indicating that the population persisted at least until the first European contact in 1499.
In Venezuela, it was found on El Caimito, a small (57 ha, 140 acres) islet just east of the outlet of Lake Maracaibo in the state of Zulia, where the only other native non-flying mammal is the opossum Marmosa robinsoni. El Caimito is separated from the mainland by a narrow, brackish channel and contains sand banks with xerophytic vegetation surrounded by marshy lagoons with Rhizospora mangle mangroves. Oryzomys gorgasi was caught in all habitats on the islet, but has not been found in other similar sites in northwestern Venezuela, where the introduced black rat is the only rodent collected. Analysis of stomach contents of El Caimito specimens indicates that the species is an omnivore, with a diet including crustaceans, insects, plant seeds, and other plant material. The crustaceans may include fiddler crabs (Uca) and a mangrove tree crab of the genus Aratus; the insects include flies (Diptera); and the plants include grass seeds. Two parasitic nematodes, Litomosoides sigmodontis (family Onchocercidae) and an undetermined species of Pterygodermatites (family Rictulariidae), are known to infect O. gorgasi. The 2009 IUCN Red List tersely indicates that the species has been found in second Venezuelan locality.
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