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The Tucuxi (Sotalia fluviatilis), alternately bufeo gris or bufeo negro (both in Peru) is a dolphin found in the rivers of the Amazon Basin. The word "tucuxi" (pronounced too-koo-shi) is derived from the Tupi language word tuchuchi-ana and has now been adopted as the species' common name. Despite being found in geographic locations similar to those of 'true' river dolphins such as the Boto, the Tucuxi is not closely related to them genetically. Instead it is classed in the oceanic dolphin family (Delphinidae). Physically the species, particularly the marine variety, resembles the Bottlenose Dolphin. However, this species is sufficiently different from the Bottlenose Dolphin that it is given its own genus, Sotalia. Animals formerly called the Tucuxi occurring in coastal and estuarine environments have recently been recognized as a distinct species Costero (Sotalia guianensis).
The Tucuxi is frequently described (see references below) as looking similar to the Bottlenose Dolphin. However it is typically smaller at around 150 cm. The dolphin is coloured light to bluish grey on its back and sides. The ventral region is much lighter, often pinkish. The dorsal fluke is typically slightly hooked. The beak is well-defined and of moderate length.
The Tucuxi Sotalia fluviatilis was described by Gervais & Deville in 1853, and the Costero Sotalia guianensis by Pierre-Joseph van Beneden in 1864. These two species were subsequently synonymized, with the two species being treated as subspecies of marine and freshwater varieties. The first to reassert differences between these two species was a three-dimensional morphometric study of Monteiro-Filho and colleagues. Subsequently a molecular analysis by Cunha and colleagues unambiguously demonstrated that Sotalia guianensis was genetically differentiated from Sotalia fluviatilis. This finding was reiterated by Caballero and colleagues with a larger number of genes. The existence of two species has been generally accepted by the scientific community, however, the IUCN still treats both species as a single species Sotalia fluviatilis.
The Tucuxi exists along much the length of the Amazon River and many of its tributaries, and is found in Brazil, Peru, south-east Colombia, and eastern Ecuador. Numerous individuals have been seen in the Orinoco River further north, though it is not clear whether these are Tucuxi or Costero.
The Tucuxi exist in small groups of about 10-15 individuals and swim in tight-knit groups, suggesting a highly developed social structure. Tucuxis are quite active and may jump clear of the water (a behavior known as breaching), somersault, spy-hop or tail-splash. They are unlikely however to approach boats.
Tucuxis have been observed to feed with other river dolphins. They feed on a wide variety of fish. Studies of growth layers suggest that the species can live up to 35 years.
The Tucuxi is endemic to the regions described above and, although no precise estimates of population are available, it is common. A significant human problem are fishing nets. Deliberate hunting in the Amazon Basin for food has also been reported. Pollution, in particular mercury poisoning of water due to gold-mining, is a particular concern for this species.
Tucuxis are observed not to maintain good health and attitude in captive environments. A few Tucuxis remain in captivity in European aquaria.
National Audubon Society Guide to Marine Mammals of the World ISBN 0-375-41141-0
Encyclopedia of Marine Mammals ISBN 0-12-551340-2
Whales, Dolphins and Porpoises, Mark Carwardine, ISBN 0-7513-2781-6
Projeto Boto - a non-profit research project that is increasing knowledge, understanding and the conservation prospects of the Amazon's two endemic dolphins - the boto (Inia geoffrensis) and the tucuxi (Sotalia fluviatilis)
Whale and Dolphin Conservation Society (WDCS)
World Wide Fund for Nature (WWF) - species profile for River Dolphins
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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article Tucuxi