The tucuxi exists along much the length of the Amazon River and many of its tributaries, and is found in Venezuela, Brazil, Peru, southeastern Colombia.
The tucuxi (Sotalia fluviatilis), alternately in Peru bufeo gris or bufeo negro, is a species of freshwater dolphin found in the rivers of the Amazon Basin. The word tucuxi 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 dolphinssuch 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 resembles the bottlenose dolphin but differs sufficiently to be placed in a separate genus, Sotalia. The costero (Sotalia guianensis), related dolphins present in coastal and estuarine environments and formerly grouped together with the tucuxi, have recently been recognized as a distinct species.
The dolphin is colored 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. There are 26 to 36 pairs of teeth in the upper and lower jaws.
The tucuxi is frequently described (see references below) as looking similar to the bottlenose dolphin, but it is typically smaller at around 1.5 m (4.9 ft).
Tucuxis have been observed to feed with other river dolphins. They feed on a wide variety of fish.
Studies of growth layers suggest the species can live up to 35 years.
The tucuxi exists 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.