Costero
Encyclopedia
The Costero is found in the coastal waters to the north and east of South America
. The common name "costero" has been suggested by Caballero and colleagues due to the species' affinity for coastal habitats. The Costero is a member of the oceanic dolphin
family (Delphinidae). Physically it resembles the Bottlenose Dolphin
. However, this species is sufficiently different from the Bottlenose Dolphin that it is given its own genus
, Sotalia. It is also known as the Guyana dolphin.
. However it is typically smaller, at only up to 210 cm length. The dolphin is colored light to bluish grey on its back and sides. The ventral region is light gray. The dorsal fin is typically slightly hooked. The beak is well-defined and of moderate length.
Researchers have recently shown that the Costero has a electroreceptive sense, and speculate this may also be the case for other toothed whales.
Sotalia fluviatilis by Pierre-Joseph van Bénéden
in 1864, the Costero Sotalia guianensis has subsequently been synonymized with Sotalia fluviatilis with the two species being treated as subspecies, or 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, however, the IUCN still treats both species as a single species Sotalia fluviatilis.
and north as far as Nicaragua
. One report exists of an animal reaching Honduras
.
In December 2006, researchers from the Southern University of Chile and the Rural Federal University of Rio de Janeiro
witnessed attempted infanticide
by a group of costero dolphins in Sepetiba Bay, Brazil
. A group of six adults separated a mother from her calf, four then keeping her at bay by ramming her and hitting her with their flukes. The other two adults rammed the calf, held it under water then threw it into the air and held it under water again. The mother was seen again in a few days, but not her calf. Since females become sexually receptive within a few days of losing a calf, and the group of attacking males was sexually interested in the female, it is possible that the infanticide occurred for this reason. Infanticide has been reported twice before in bottlenose dolphins, but is thought to be generally uncommon among cetaceans.
delta region. Many of these animals are used as shark
fishing bait, and their organs are sold as fetishes. Another major problem in some areas are collisions with boats. Possible natural predators are the Orca
and the bull shark
.
The Guiana dolphin is listed on Appendix II 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.
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
. The common name "costero" has been suggested by Caballero and colleagues due to the species' affinity for coastal habitats. The Costero is a member of the oceanic dolphin
Oceanic dolphin
Oceanic dolphins are the members of the Delphinidae family of cetaceans. These marine mammals are related to whales and porpoises. They are found worldwide, mostly in the shallower seas of the continental shelves...
family (Delphinidae). Physically it resembles the Bottlenose Dolphin
Bottlenose Dolphin
Bottlenose dolphins, the genus Tursiops, are the most common and well-known members of the family Delphinidae, the family of oceanic dolphins. Recent molecular studies show the genus contains two species, the common bottlenose dolphin and the Indo-Pacific bottlenose dolphin , instead of one...
. However, this species is sufficiently different from the Bottlenose Dolphin that it is given its own genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
, Sotalia. It is also known as the Guyana dolphin.
Description
The Costero is frequently described as looking similar to the bottlenose dolphinBottlenose Dolphin
Bottlenose dolphins, the genus Tursiops, are the most common and well-known members of the family Delphinidae, the family of oceanic dolphins. Recent molecular studies show the genus contains two species, the common bottlenose dolphin and the Indo-Pacific bottlenose dolphin , instead of one...
. However it is typically smaller, at only up to 210 cm length. The dolphin is colored light to bluish grey on its back and sides. The ventral region is light gray. The dorsal fin is typically slightly hooked. The beak is well-defined and of moderate length.
Researchers have recently shown that the Costero has a electroreceptive sense, and speculate this may also be the case for other toothed whales.
Taxonomy
Although described as species distinct from the TucuxiTucuxi
The Tucuxi , alternately bufeo gris or bufeo negro is a 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...
Sotalia fluviatilis by Pierre-Joseph van Bénéden
Pierre-Joseph van Beneden
Pierre-Joseph van Beneden was a Belgian zoologist and paleontologist.Born in Mechelen, Belgium, he studied medicine at the University of Louvain, and studied zoology in Paris under Georges Cuvier...
in 1864, the Costero Sotalia guianensis has subsequently been synonymized with Sotalia fluviatilis with the two species being treated as subspecies, or 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, however, the IUCN still treats both species as a single species Sotalia fluviatilis.
Distribution
The Costero is found close to estuaries, inlets and other protected shallow water areas around the eastern and northern South America coast. It has been reported as far south as southern BrazilBrazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
and north as far as Nicaragua
Nicaragua
Nicaragua is the largest country in the Central American American isthmus, bordered by Honduras to the north and Costa Rica to the south. The country is situated between 11 and 14 degrees north of the Equator in the Northern Hemisphere, which places it entirely within the tropics. The Pacific Ocean...
. One report exists of an animal reaching Honduras
Honduras
Honduras is a republic in Central America. It was previously known as Spanish Honduras to differentiate it from British Honduras, which became the modern-day state of Belize...
.
Behavior
This species forms small groups of about 10-15 individuals, occasionally up to 30 and swim in tight-knit groups, suggesting a highly developed social structure. They 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. They feed on a wide variety of fish. Studies of growth layers suggest that the species can live up to 30 years.In December 2006, researchers from the Southern University of Chile and the Rural Federal University of Rio de Janeiro
Universidade Federal Rural do Rio de Janeiro
The Federal Rural University of Rio de janeiro is a centenary Brazilian university located in the city of Seropédica in the State of Rio de Janeiro in Brazil...
witnessed attempted infanticide
Infanticide (zoology)
In animals, infanticide involves the killing of young offspring by a mature animal of its own species, and is studied in zoology, specifically in the field of ethology. Ovicide is the analogous destruction of eggs. Although human infanticide has been widely studied, the practice has been observed...
by a group of costero dolphins in Sepetiba Bay, Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
. A group of six adults separated a mother from her calf, four then keeping her at bay by ramming her and hitting her with their flukes. The other two adults rammed the calf, held it under water then threw it into the air and held it under water again. The mother was seen again in a few days, but not her calf. Since females become sexually receptive within a few days of losing a calf, and the group of attacking males was sexually interested in the female, it is possible that the infanticide occurred for this reason. Infanticide has been reported twice before in bottlenose dolphins, but is thought to be generally uncommon among cetaceans.
Conservation
The Costero appears to be relatively common, however, it gets frequently entangled in nets of the coastal fishing fleets. It is estimated that at least 2,000 animals are killed by entanglement per year in the Amazon RiverAmazon River
The Amazon of South America is the second longest river in the world and by far the largest by waterflow with an average discharge greater than the next seven largest rivers combined...
delta region. Many of these animals are used as shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....
fishing bait, and their organs are sold as fetishes. Another major problem in some areas are collisions with boats. Possible natural predators are the Orca
Orca
The killer whale , commonly referred to as the orca, and less commonly as the blackfish, is a toothed whale belonging to the oceanic dolphin family. Killer whales are found in all oceans, from the frigid Arctic and Antarctic regions to tropical seas...
and the bull shark
Bull shark
The bull shark, Carcharhinus leucas, also known as Zambezi shark or unofficially known as Zambi in Africa and Nicaragua shark in Nicaragua, is a shark common worldwide in warm, shallow waters along coasts and in rivers...
.
The Guiana dolphin is listed on Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals (CMS
Bonn Convention
The Convention on the Conservation of Migratory Species of Wild Animals aims to conserve terrestrial, marine and avian migratory species throughout their range...
). 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.