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Sotalia fluviatilis


The unique name of this cetacean is pronounced “tucushi” and comes from the Tupi language, typical of South America. It is also known as gray bufeo and black bufeo in the area.

This little-known species is physically similar to the bottlenose dolphin (Tursiops truncatus) except for its size and other minor details. It is found in fresh and salty waters but is not genetically related to the South American river dolphins. Described initially in 1853, the Tucuxi is a small dolphin.

Order: Cetacea
Family: Delphinidae
Genus: Sotalia

The author of the image: Archilider.


The shape of its body is similar to that of the bottlenose dolphin as it is fusiform and slightly robust. It has a triangular dorsal fin slightly hooked. Its snout is long, very pronounced and narrow. Its pectoral flippers are large.

Weight and size.
It is one of the smallest cetaceans of the Delphinidae family, and there is no presence of sexual dimorphism. Adults have an average length of 2.1-2.2 meters and a weight of 35 to 55 kilograms. Individuals living in freshwater have a shorter length, estimated at 1.5 meters.

Skin Coloration.
The color of its dorsal skin varies being either bluish, gray or dark brown. The lower part of its body is white, light gray or pink and the sides are a shade between the dorsal and ventral colors. It has a dark strip blended between the snout and each of the pectoral flippers. Some populations have yellow stripes on the sides and a clear spot on the dorsal fin.

Distinctive characteristics.
Most specimens have a white patch on the tip of the snout.
There are two ecotypes of this species, one living in ocean waters of the Atlantic Ocean and another dwelling in the Amazon and Orinoco Rivers.


The Tucuxi is a species endemic to South American waters; the tucuxi inhabits waters of Brazil, Panama, Peru, Ecuador, Colombia, Nicaragua, Venezuela and probably Honduras. Its distribution range starts from this last country or Panama and runs along the east South American coasts ending in southern Brazil.

There are two ecotypes of this species, one living in the waters of the Atlantic Ocean and other that dwells in the Amazon and Orinoco rivers. Those who live in the ocean stay near the coasts, in estuaries, and bays. The freshwater ecotype, inhabit the channels of the rivers mentioned above reaching upriver up to 2,500 kilometers in the Amazon and 250 kilometers in the Orinoco.


The tucuxi is a carnivorous dolphin. It submerges for about 30 seconds to search for food, and they frequent the confluence areas because it is a zone suitable for the development of species such as plankton which in turn attracts many species of fish. Therefore, this dolphin usually goes to the confluences of bodies of water, but it also goes to places near the coasts.

Ray-finned fishes (Actinopterygii class), octopuses, squids, and shrimps are the main part of its diet. If they are in the open ocean, they prefer to feed on small fishes grouped in schools, and near the coasts, they prefer to catch pelagic or demersal fishes and cephalopods.

The tucuxi living in the Amazon consume around 28 species of fish, and within this set, they prefer those that belong to the family Curimatidae, because they represent 52 percent of their total diet.


It is considered a shy dolphin which never get close to boats or people and whose swimming is slow, but this does not mean that is “not active.” On the contrary, it spends most of the day doing activities, and its leaps out of the water are impressive. It can leap up to 1 meter out of the water and executes jumps, tumbles and blows with its pectoral flippers and the tail either alone or in coordination with other members of its pod. The only thing they do not do is riding the bow waves of boats, which is evident, as they do not come close to them.

This dolphin has a social structure based on small groups containing 2 to 6 members. In most cases, the pod is made up of 9-20 individuals for the ecotype living in freshwater and up to 50 members for those dwelling in the coastal waters of the Atlantic. Occasionally the pods associate with other species of dolphins, such as the Amazon pink dolphin (Inia geoffrensis). In any case, it seems that the adult males dominate the pods and they are the ones followed by other members.

The flood season is perfect for swimming through small tributaries, but they do not dare to leave the main river channels and enter into flooded forests. On the other hand, they communicate through whistles and clicks. Their sounds are higher than those of other dolphins, and they produce them while feeding, perhaps to call their peers.


Researchers believe that the females of this species mate with several males in the same breeding period (polyandry). The courtship includes an aggressive behavior of males.

Both genders reach sexual maturity at six years of age. The gestation period lasts between ten and twelve months, and the calf is born at some point in the autumn. The offspring can have a length from 71 to 106 centimeters.


Conservation status: Data Deficient.

The tucuxi has a conservation status of “Data Deficient” in the Red List of the International Union for the Conservation of Nature (IUCN). The size of the total population is unknown, but it is true that it is vulnerable to the effects of human activities such as:

– Bycatch.
– Direct hunting.
– Prey Overfishing.
– Habitat Contamination.
– Acoustic pollution.
– Boat collisions.
– Construction of dams that reduce and segment their distribution.

This dolphin is in Appendix II of the CMS (Convention on Migratory Species) for animals in need of conservation agreements and in Appendix I of CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora), which contains species with a higher danger of extinction and whose trade is prohibited. Also, the International Whaling Commission (IWC) initiated a plan called Project Sotalia with the aim of studying this species thoroughly.



William F. Perrin, Bernd Würsig, J.G.M. ‘Hans’ Thewissen. Encyclopedia of Marine Mammals. Academic Press, 2009. Page 1188.