Tucuxi

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 ft 11 in). The dolphin is colored light to bluish grey on its back and sides. The ventral region is much lighter, often pinkish. It is theorized that this pinkish color may be caused or intensified by increased blood flow. 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 has one of the largest known encephalization quotients among mammals.

The tucuxi exists along much of the length of the Amazon River and many of its tributaries, and is found in Venezuela, Brazil, Peru, Ecuador, and southeastern Colombia. Numerous individuals have been seen in the Orinoco River further north, though it is not clear whether these are tucuxi or costero. The tucuxi has recently been found to inhabit a larger range, including the northeast portion of Brazil such as the state of Amapa, which includes more basins than the Amazon basin. This species occurs in freshwater habitats only.

Tucuxis forage in tight groups, often chasing fish in rapid dashes just below the water surface, with fish jumping out of their way. Thirty species of fish are known to be prey, some living in protected lakes and channels, while others occur in fast-flowing rivers.

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. 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 the species can live up to 35 years . The oldest known animal was 36 years of age.

The oil and fat in the skin of tucuxi is used in local traditional medicine as an ointment to be rubbed on wounds or sore body parts. The ointment is thought to treat illnesses such as hemorrhoids, rheumatism, and arthritis, while the teeth are used in a powder form to treat asthma.