The tucuxi (''Sotalia fluviatilis''), alternatively known in
Peru
, image_flag = Flag of Peru.svg
, image_coat = Escudo nacional del Perú.svg
, other_symbol = Great Seal of the State
, other_symbol_type = National seal
, national_motto = "Firm and Happy f ...
''bufeo gris'' or ''bufeo negro'', is a species of freshwater
dolphin
A dolphin is an aquatic mammal within the infraorder Cetacea. Dolphin species belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontoporiidae (the br ...
found in the rivers of the
Amazon basin
The Amazon basin is the part of South America drained by the Amazon River and its tributaries. The Amazon drainage basin covers an area of about , or about 35.5 percent of the South American continent. It is located in the countries of Boliv ...
. The word ''tucuxi'' is derived from the
Tupi language
Old Tupi, Ancient Tupi or Classical Tupi (also spelled as Tupí) is an extinct Tupian language which was spoken by the aboriginal Tupi people of Brazil, mostly those who inhabited coastal regions in South and Southeast Brazil. It belongs to t ...
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 dolphin
River dolphins are a polyphyletic group of fully aquatic mammals that reside exclusively in freshwater or brackish water. They are an informal grouping of dolphins, which itself is a paraphyletic group within the infraorder Cetacea. Extant riv ...
s such as the
boto, the tucuxi is not closely related to them genetically. Instead, it is classed in the
oceanic dolphin
Oceanic dolphins or Delphinidae are a widely distributed family of dolphins that live in the sea. Close to forty extant species are recognised. They include several big species whose common names contain "whale" rather than "dolphin", such as th ...
family (Delphinidae).
Physically, the species resembles the
bottlenose dolphin
Bottlenose dolphins are aquatic mammals in the genus ''Tursiops.'' They are common, cosmopolitan members of the family Delphinidae, the family of oceanic dolphins. Molecular studies show the genus definitively contains two species: the comm ...
s, but differs sufficiently to be placed in a separate
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomencla ...
, ''
Sotalia''. The
Guiana dolphin (''Sotalia guianensis''), a related dolphin present in coastal and
estuarine
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...
environments and formerly grouped together with the tucuxi, have recently been recognized as a distinct species.
Description
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). The dolphin is colored light to bluish grey on its back and sides. The
ventral
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...
region is much lighter, often pinkish. It is theorized that this pinkish color may be caused or intensified by increased blood flow. The
dorsal
Dorsal (from Latin ''dorsum'' ‘back’) may refer to:
* Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism
* Dorsal, positioned on top of an aircraft's fuselage
* Dorsal co ...
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 quotient
Encephalization quotient (EQ), encephalization level (EL), or just encephalization is a relative brain size measure that is defined as the ratio between observed to predicted brain mass for an animal of a given size, based on nonlinear regress ...
s among mammals.
Taxonomy
The tucuxi (''Sotalia fluviatilis'') was described by
Gervais and
Deville in 1853, and the
costero (''Sotalia guianensis'') by
Pierre-Joseph van Bénéden 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.
Distribution
The tucuxi exists along much of the length of the
Amazon River
The Amazon River (, ; es, Río Amazonas, pt, Rio Amazonas) in South America is the largest river by discharge volume of water in the world, and the disputed longest river system in the world in comparison to the Nile.
The headwaters of ...
and many of its tributaries, and is found in
Venezuela
Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in t ...
,
Brazil,
Peru
, image_flag = Flag of Peru.svg
, image_coat = Escudo nacional del Perú.svg
, other_symbol = Great Seal of the State
, other_symbol_type = National seal
, national_motto = "Firm and Happy f ...
,
Ecuador
Ecuador ( ; ; Quechua: ''Ikwayur''; Shuar: ''Ecuador'' or ''Ekuatur''), officially the Republic of Ecuador ( es, República del Ecuador, which literally translates as "Republic of the Equator"; Quechua: ''Ikwadur Ripuwlika''; Shuar: ''Ekua ...
, southeastern
Colombia. Numerous individuals have been seen in the
Orinoco River
The Orinoco () is one of the longest rivers in South America at . Its drainage basin, sometimes known as the Orinoquia, covers , with 76.3 percent of it in Venezuela and the remainder in Colombia. It is the fourth largest river in the wo ...
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.
Food and foraging
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.
[
]
Behaviour
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.[
]
Threats
Medicinal use
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.
Magic and religious use
The eyes, teeth, and genital organs of tucuxi are sold throughout Northern Brazil as magical charms that promote good luck, love, and financial rewards. Baths are also created with these body parts and are meant to help one attract sexual partners if they bathed in the water. Other products such as perfumes and powders made with the genital organs are sold as aphrodisiacs. The number of dolphins harvested for magical or religious purposes and its effect on tucuxi populations is unknown.
Fishing
Interactions of tucuxi dolphins with fishing activity is common in the Western Brazilian Amazon. Tucuxi forage on schooling fish that are also important species for commercial fishing in the area. They are particularly vulnerable to entanglement in commercial fishing nets in the lower Japurá River. The carcasses of the dolphins caught incidentally or intentionally are often used as bait for piracatinga fishing.
Habitat Degradation and Loss
The tucuxi's habitat has been greatly affected by anthropogenic activities including the expansion of hydroelectric projects, which usually results in isolation where a dam is built. Pollution from human activity has also degraded the quality of the habitat and increases the chance for tucuxis to consume heavy metals.
Conservation
The tucuxi is endemic to the regions described above; although no precise estimates of population are available, it is common. A significant human problem is fishing nets. Deliberate hunting in the Amazon basin for food has also been reported. Pollution, in particular, mercury poisoning
Mercury poisoning is a type of metal poisoning due to exposure to mercury. Symptoms depend upon the type, dose, method, and duration of exposure. They may include muscle weakness, poor coordination, numbness in the hands and feet, skin rashes ...
of water
Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...
due to gold mining
Gold mining is the extraction of gold resources by mining. Historically, mining gold from alluvial deposits used manual separation processes, such as gold panning. However, with the expansion of gold mining to ores that are not on the surface, ...
, is a particular concern for this species. The IUCN
The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...
also cites habitat fragmentation
Habitat fragmentation describes the emergence of discontinuities (fragmentation) in an organism's preferred environment (habitat), causing population fragmentation and ecosystem decay. Causes of habitat fragmentation include geological process ...
by dam construction as a threat, though more detailed study is necessary.
Tucuxis are observed not to maintain good health and attitude in captive environments. A few tucuxis remained in captivity in European aquaria, but the last one ("Paco") died in 2009 in the Zoo
A zoo (short for zoological garden; also called an animal park or menagerie) is a facility in which animals are kept within enclosures for public exhibition and often bred for conservation purposes.
The term ''zoological garden'' refers to zool ...
of Münster, Germany.
The tucuxi is listed on Appendix II[Appendix II]
" of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). As amended by the Conference of the Parties in 1985, 1988, 1991, 1994, 1997, 1999, 2002, 2005 and 2008. Effective: 5 March 2009
/ref> of the Convention on the Conservation of Migratory Species of Wild Animals ( CMS). It is listed on Appendix II as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.
See also
*List of cetaceans
Cetacea is an infraorder that comprises the 94 species of whales, dolphins, and porpoises. It is divided into toothed whales (Odontoceti) and baleen whales (Mysticeti), which diverged from each other in the Eocene some 50 million years ago (mya). ...
* Environmental issues in Brazil
References
*''National Audubon Society Guide to Marine Mammals of the World''
*''Encyclopedia of Marine Mammals''
*''Whales, Dolphins and Porpoises'', Mark Carwardine,
External links
Whale and Dolphin Conservation Society (WDCS)
{{Taxonbar , from=Q935680
Oceanic dolphins
Mammals of South America
Mammals of Brazil
Mammals of Peru
Mammals described in 1853
Taxa named by Émile Deville