Tucuxi dolphin (Sotalia fluviatilis)

Description

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Tucuxi dolphin fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
• Print factsheet

Tucuxi dolphin description

The tucuxi dolphin (pronounced ‘too-koo-shee’) quite closely resembles the bottlenose dolphin, but smaller. It is blue to light grey on the back, and fades to white or whitish-pink on the belly. There is a dark bar between the mouth and the flipper. The beak is slender and long, and the dorsal fin is triangular and slightly hooked at the tip ⁽²⁾. Both the beak and the dorsal fin may be tipped with white ⁽⁵⁾. Some marine populations have yellow-orange sides with a bright patch on the dorsal fin ⁽⁵⁾.

Also known as

estuarine dolphin, grey dolphin, grey river dolphin, Guianian river dolphin.

French

Dauphin De L'Amazon, Sotalie.

Spanish

Bufeo Negro, Bufo Negro.

Size

Length of freshwater subspecies: 150 cm ⁽²⁾

Length of marine subspecies: 210 – 220 cm ⁽²⁾

Length of newborn: 70 – 90 cm ⁽³⁾

Adult weight: 35 – 45 kg ⁽⁴⁾

Tucuxi dolphin biology

Little is known of the reproductive habits of the tucuxi dolphin. The freshwater subspecies calves during the low water period of October and November ⁽²⁾, after an 11 to 12 month gestation. It is thought to be polyandrous (where each female has more than one male partner), and aggression between males is seen during courtship ⁽⁵⁾.

The seasonal fluctuation in river water levels has a great influence on the freshwater subspecies. It enters lakes during high water but leaves as the waters begin to fall to avoid being trapped ⁽²⁾. A shy dolphin, the tucuxi tends to be most active during the early morning and late afternoon, but is usually a slow swimmer that jumps infrequently ⁽⁵⁾. It dives for around 30 seconds ⁽⁴⁾, and uses echolocation to communicate as well as to catch fish and shrimp ⁽⁵⁾. Group size varies, but can be up to 20 in freshwater or 50 in the marine subspecies ⁽³⁾.

Tucuxi dolphin range

Occurring in the river systems of the Amazon and the Orinoco, as well as along the coasts from Brazil to Nicaragua, the tucuxi dolphin is split into two subspecies. The freshwater subspecies, Sotalia fluviatilis fluviatilis, inhabits only fresh water and is found as much as 250 kilometres up the Orinoco River system and as much as 2,500 km up the Amazon River system. The marine subspecies, Sotalia fluviatilis guianensis, is found in the coastal estuaries and bays of the east coast of South America as far south as the Brazilian city of Florianópolis ⁽²⁾.

Tucuxi dolphin habitat

The freshwater subspecies inhabits rivers and lakes, but is not found in flooded forests and avoids rapids, whereas the marine subspecies inhabits shallow, protected estuaries and bays ⁽²⁾.

Tucuxi dolphin status

The tucuxi dolphin is classified as Data Deficient on the IUCN Red List ⁽¹⁾, and is listed on Appendix I of CITES ⁽⁵⁾. It is also listed on Appendix II of the Convention on Migratory Species ⁽²⁾.

Tucuxi dolphin threats

The tucuxi dolphin is regularly caught accidentally in gillnets of large fishing trawlers, and is the most common cetacean in the by-catch of coastal fisheries in the south Caribbean Sea. Intentional hunting appears to be rare, but does take place for meat to eat, for blubber to be used as shark bait, and for the genital organs and eyes which are sold as love amulets ⁽¹⁾. A major potential threat is a proposal for the construction of hydroelectric dams, which would cause population fragmentation and increased inbreeding, as well as the extinction of the migratory fish that constitute the diet of the freshwater tucuxi dolphin ⁽²⁾. Pollution from heavy metals, banned pesticides and noise are also concerns, as is habitat loss ⁽¹⁾.

Tucuxi dolphin conservation

The superstition of fishermen, who believe the tucuxi dolphin to be a sacred animal that brings the bodies of drowned people back to the shore, has ensured that it has rarely been targeted as a food item ⁽⁶⁾. In 1994, the International Whaling Commission’s (IWC) Scientific Committee urged member states to reduce by-catch and monitor populations ⁽¹⁾. The IWC had previously started the Sotalia Project with the organisation ‘Brasil’s Biologists’, which sets out to study the behaviour and habitat needs of the tucuxi dolphin, and has managed to build a significant collection of photo identifications ⁽⁶⁾.

To learn more about a Whitley Award-winning conservation project for this species, click here.

View information on this species at the UNEP World Conservation Monitoring Centre.

To help conserve this species by working in the field with Earthwatch, click here.

Find out more

For further information on the tucuxi see:

• Convention on Migratory Species:
  http://www.cms.int/reports/small_cetaceans/data/S_fluviatilis/s_fluviatilis.htm

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Glossary

By-catch

In the fishing industry, the part of the catch made up of non-target species.

Subspecies

A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.

References

1. IUCN Red List (June, 2009)
   http://www.iucnredlist.org
2. Convention on Migratory Species (November, 2004)
   http://www.cms.int/reports/small_cetaceans/data/S_fluviatilis/s_fluviatilis.htm
3. Sea Map (November, 2004)
   http://seamap.env.duke.edu/species/tsn/180422
4. Cetaceans of the World (November, 2004)
   http://www.sci.tamucc.edu/tmmsn/29Species/MoreSpec/tucuxi.html
5. CITES (November, 2004)
   http://www.cites.org
6. Animal Diversity Web (November, 2004)
   http://animaldiversity.ummz.umich.edu/site/accounts/information/Sotalia_fluviatilis.html