Amazon river dolphin
Inia geoffrensis, commonly known as the Amazon river dolphin, is a freshwater river dolphin endemic to the Orinoco, Amazon and Araguaia/Tocantins River systems of Brazil, Peru, Bolivia, Ecuador, Colombia and Venezuela. It was previously listed as a vulnerable species by the IUCN due to pollution, overfishing, excessive boat traffic and habitat loss but in 2011 it was changed to data deficient due to a lack of current information about threats, ecololgy, and population numbers and trends.
The Amazon river dolphin is one of a handful of river dolphins included in the paraphyletic group classified as the superfamily Platanistoidea. Although not a large cetacean in general terms, this dolphin is the largest cetacean to spend most of its life in freshwater; it can grow larger than a human. Body length can range from 1.53 to 2.4 m (5.0 to 7.9 ft), depending on subspecies. Females are typically larger than males. The largest female Amazon river dolphins can range up to 2.5 m (8.2 ft) in length and weigh 98.5 kg (217 lb). The largest male dolphins can range up to 2.0 m (6.6 ft) in length and weigh 94 kg (210 lb).
They have unfused neck vertebrae, enabling them to turn their heads 180 degrees. Their flexibility is important in navigating through the flooded forests. Also, they possess long beaks which contain 24 to 34 conical and molar-type teeth on each side of the jaws.
The species was described by Henri Marie Ducrotay de Blainville in 1817. Rice's 1998 classification lists a single species, Inia geoffrensis in the genus Inia, with three recognized subspecies. Some older classifications, as well as some recent publications, listed the boliviensis population as a separate species. In 2012 the Society for Marine Mammalogy began considering the Bolivian (Inia geoffrensis boliviensis) and Amazonian (Inia geoffrensis geoffrensis) subspecies as full species Inia boliviensis and Inia geoffrensis, respectively; however, much of the scientific community consider the boliviensis population to be a subspecies of Inia geoffrensis. The genus Inia separated from its sister taxon during the Miocene epoch.
The two currently recognized species are:
- I. g. geoffrensis — distributed in the Amazon and Araguaia/Tocantins basins (excluding the Madeira River drainage, upstream of the Teotonio Rapids in Rondônia)
- I. g. humboldtiana — distributed in the Orinoco basin
- I. boliviensis — distributed in the Bolivian subbasin of the Amazon basin upstream of the Teotonio Rapids in Rondônia
The Amazon river dolphin is found throughout the Amazon and Orinoco. It is particularly abundant in lowland rivers with extensive floodplains. During the annual rainy season, these rivers flood large areas of forests and marshes along their banks. The Amazon river dolphin specializes in hunting in these habitats, taking advantage of its unusually flexible neck and spinal cord to maneuver among the underwater tree trunks, and using its long snout to extract prey fish from hiding places in hollow logs and thickets of submerged vegetation.
When the water levels drop, the dolphins move either into the main river channels or into large lakes in the forest, and take advantage of the concentrated prey in these reduced water bodies. They feed on crustaceans, crabs, small turtles, catfish, piranha, shrimp, and other fish.
The male reaches sexual maturity at about 7 feet (2 m) and the female at about 5.5 feet (1.7 m). Most calves are born between July and September after a gestation period of 9 to 12 months; they are about 32 inches long at birth (80 cm) and weigh about 15 pounds.
The young follow their parents closely for a few months, and often two adults are seen swimming with two or more small juveniles.
Amazonian folklore includes mention of shapeshifters called encantados. Their natural form is the boto, but at night they are able to transform into beautiful men and women who often show up parties, seduce people, and produce illegitimate children with humans.
The Amazon river 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 unfavorable conservation status or would benefit significantly from international co-operation organized by tailored agreements. In September 2012, Bolivian President Evo Morales enacted a law to protect the dolphin and declared it a national treasure.
In popular culture
In traditional Amazon River folklore, at night, an Amazon river dolphin becomes a handsome young man who seduces girls, impregnates them, and then returns to the river in the morning to become a dolphin again. This dolphin shapeshifter is called an encantado. It has been suggested that the myth arose partly because dolphin genitalia bear a resemblance to those of humans. Others believe the myth served (and still serves) as a way of hiding the incestuous relations which are quite common in some small, isolated communities along the river. In the area, there are tales that it is bad luck to kill a dolphin. Legend also states that if a person makes eye contact with an Amazon river dolphin, he or she will have lifelong nightmares. Local legends also state that the dolphin is the guardian of the Amazonian manatee, and that, should one wish to find a manatee, one must first make peace with the dolphin.
Associated with these legends is the use of various fetishes, such as dried eyeballs and genitalia. These may or may not be accompanied by the intervention of a shaman. A recent study has shown, despite the claim of the seller and the belief of the buyers, none of these fetishes are derived from the boto. They are derived from Sotalia guianensis, are most likely harvested along the coast and the Amazon River delta, and then are traded up the Amazon River. In inland cities far from the coast, many, if not most, of the fetishes are derived from domestic animals such as sheep and pigs.
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