Amazon river dolphin

Amazon river dolphin
Size compared to an average human
Conservation status

Data Deficient  (IUCN 3.1)[1]
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Subclass: Eutheria
Order: Cetacea
Suborder: Odontoceti
Superfamily: Inioidea
Family: Iniidae
Genus: Inia
Species: I. geoffrensis
Binomial name
Inia geoffrensis
Blainville, 1817
Amazon river dolphin range

The Amazon river dolphin, or pink river dolphin, Inia geoffrensis, 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, ecology, and population numbers and trends.[1]

Other common names of the species include boto, boto cor-de-rosa, boto vermelho, bouto, bufeo, tonina, yeyekeo (in Wao terero, the language of the indigenous Waorani people), and pink dolphin.[1]

Description

The Amazon river dolphin is one of the river dolphins formerly included in the super family Platanistoidea, making it paraphyletic; it has since been moved to Inioidea. Although not a large cetacean in general terms, this dolphin is the largest freshwater cetacean; 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 (207 lb).[2][3]

They have unfused neck vertebrae, enabling them to turn their heads 90°. 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.[4]

In color, these dolphins can be either light gray or carnation pink.

Taxonomy

The species was described by Henri Marie Ducrotay de Blainville in 1817. Rice's 1998 classification[5] lists a single species, Inia geoffrensis in the genus Inia, with three recognised subspecies. Some older classifications, as well as some recent publications,[6] listed the boliviensis population as a separate species. In 2012 the Society for Marine Mammalogy[7] began considering the Bolivian (I. g. boliviensis) and Amazonian (I. g. geoffrensis) subspecies as full species Inia boliviensis and Inia geoffrensis, respectively; however, many of the scientific community consider the I. g. boliviensis population to be a subspecies of I. geoffrensis. The genus Inia separated from its sister taxon during the Miocene epoch.[8]

The two currently recognized species are:

The Amazon river dolphin is the closest relative of the newly identified Araguaian river dolphin, which is believed to have become physically separated and isolated in the Araguaia/Tocantins basin approximately two million years ago. Araguaian botos have fewer rows of teeth than the closely related Amazon botos.[9]

Ecology

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, using 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, shrimp, and piranha and other fish.[4]

Behavior

Adult males have been observed carrying objects in their mouths, objects such as branches or other floating vegetation, or balls of hardened clay. The males appear to carry these objects as a sociosexual display which is part of their mating system. The behaviour is "triggered by an unusually large number of adult males and/or adult females in a group, or perhaps it attracts such into the group. A plausible explanation of the results is that object carrying is aimed at females and is stimulated by the number of females in the group, while aggression is aimed at other adult males and is stimulated by object carrying in the group."[10]

The male reaches sexual maturity at about 2 m (6.6 ft) and the female at about 1.7 m (5.6 ft). Most calves are born between July and September after a gestation period of 9 to 12 months; they are about 0.81 m (2.7 ft) long at birth and weigh about 6.8 kg (15 lb).[4] The young follow their parents closely for a few months, and often two adults are seen swimming with two or more small juveniles.

Human interaction

A trained Amazon river dolphin at the Acuario de Valencia

The Amazon river dolphin is listed on appendix II[11] 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 organized by tailored agreements. In September 2012, Bolivian President Evo Morales enacted a law to protect the dolphin and declared it a national treasure.[12]

The region of the Amazon in Brazil has an extension of 5,000,000 km2 (1,900,000 sq mi) containing diverse fundamental ecosystems.[13][14] One of these ecosystems is a floodplain, or a várzea forest, and is home to a large number of fish species which are an essential resource for human consumption.[15] The várzea is also a major source of income through excessive local commercialized fishing.[13][16][17] Várzea consist of muddy river waters containing a vast number and diversity of nutrient rich species.[10] The abundance of distinct fish species lures the Amazon River dolphin into the várzea areas of high water occurrences during the seasonal flooding.[18]

In addition to attracting predators such as the Amazon river dolphin, these high-water occurrences are an ideal location to draw in the local fisheries. Human fishing activities directly compete with the dolphins for the same fish species, the tambaqui (Colossoma macropomum) and the pirapitinga (Piaractus brachypomus), resulting in deliberate or unintentional catches of the Amazon river dolphin.[19][20][21][13][22][23][24][25] The local fishermen overfish and when the Amazon River dolphins remove the commercialized fish from the nets and lines, it causes damages to the equipment and the capture, as well as a negative reaction from the local fishermen.[21] [23][24] The negative reactions of the local fishermen is also attributed to the Brazilian Institute of Environment and Renewable Natural Resources prohibiting from killing the Amazon river dolphin, yet not compensating the fishermen for the damage done to their equipment and capture.[25]

During the process of catching the commercialized fish, the Amazon river dolphins get caught in the nets and exhaust themselves until they die, or the local fishermen deliberately kill the dolphins that become entangled in their nets.[15] The carcasses are discarded, consumed, or used as bait to attract a scavenger catfish, the piracatinga (Calophysus macropterus).[15][26] The use of the Amazon river dolphin carcass as bait for the piracatinga dates back from 2000.[26] The increasing consumption demand by the local inhabitants and Colombia for the piracatinga has created a market for distribution of the Amazon river dolphin carcasses to be used as bait throughout these regions.[25]

As an example, of the 15 dolphin carcases found in the Japurá River in 2010-2011 surveys, 73% of the dolphins were killed for bait, disposed of, or abandoned in entangled gillnets.[15] The data do not fully represent the actual overall number of deaths of the Amazon river dolphins, whether accidental or intentional, because a variety of factors make it extremely complicated to record and medically examine all the carcasses.[15][20][23] Scavenger species feed upon the carcasses and the complexity of the river currents make it nearly impossible to locate all the carcasses.[15] More importantly, the local fishermen do not report these deaths out of fear that a legal course of action will be taken against them,[15] as the Amazon river dolphin and other cetaceans are protected under the Brazilian federal law prohibiting any takes, harassments, and kills of the species.[27]

Cultural references

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. The myth has been suggested to have arisen 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.[28] In the area, tales relate 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 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.[28] 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 is 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.[29]

See also

Wikimedia Commons has media related to Inia geoffrensis.
Wikispecies has information related to: Amazon river dolphin


References

  1. ↑ 1.0 1.1 1.2 Reeves, R.R., Jefferson, T.A., Karczmarski, L., Laidre, K., O’Corry-Crowe, G., Rojas-Bracho, L., Secchi, E.R., Slooten, E., Smith, B.D., Wang, J.Y. & Zhou, K. (2013). "Inia geoffrensis". IUCN Red List of Threatened Species. Version 2014.3. International Union for Conservation of Nature. Retrieved 9 April 2015. Database entry includes a lengthy justification of why this species is data-deficient.
  2. ↑ "Animal Info - Boto (Amazon river dolphin)". Animal Info - Endangered Animals. June 7, 2006. Retrieved December 6, 2011.
  3. ↑ Robin C. Best & Vera M.F. da Silva (1993). "Inia geoffrensis" (PDF). Mammalian Species (The American Society of Mammalogists) (426): 1–8.
  4. ↑ 4.0 4.1 4.2 American Cetacean Society Fact Sheet. "Boto (Amazon river dolphin)". American Cetacean Society. Retrieved December 6, 2011.
  5. ↑ Rice, D. W. (1998). Marine mammals of the world: systematics and distribution. Society of Marine Mammalogy Special Publication Number 4. p. 231.
  6. ↑ Martínez-Agüero, M., S. Flores-Ramírez, and M. Ruiz-García (2006). "First report of major histocompatibility complex class II loci from the Amazon pink river dolphin (genus Inia)" (PDF). Genetics and Molecular Research 5 (3): 421–431. PMID 17117356.
  7. ↑ Committee on Taxonomy. 2012. List of marine mammal species and subspecies. Society for Marine Mammalogy, www.marinemammalscience.org, consulted on May 6, 2012.
  8. ↑ Hamilton, H., S. Caballero, A. G. Collins, and R. L. Brownell Jr. (2001). "Evolution of river dolphins". Proceedings of the Royal Society B 268 (1466): 549–556. doi:10.1098/rspb.2000.1385. PMC 1088639. PMID 11296868.
  9. ↑ Hrbek, Tomas; Da Silva, Vera Maria Ferreira; Dutra, Nicole; Gravena, Waleska; Martin, Anthony R.; Farias, Izeni Pires (2014-01-22). Turvey, Samuel T., ed. "A New Species of River Dolphin from Brazil or: How Little Do We Know Our Biodiversity". PLOS ONE 9: e83623. doi:10.1371/journal.pone.0083623.
  10. ↑ 10.0 10.1 Martin A.R., Da Silva V.M.F. and Rothery P. (2008) "Object carrying as social–sexual display in an aquatic mammal" Animal Behavior, Biology Letters, 4: 1243–2145.
  11. ↑ 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.
  12. ↑ "Bolivia enacts law to protect Amazon pink dolphins". BBC News. 18 September 2012.
  13. ↑ 13.0 13.1 13.2 Silvano, R.A.M.; Ramires, M.; Zuanon, J. (2009). "Effects of fisheries management on fish communities in the floodplain lakes of a Brazilian Amazonian Reserve". Ecology of Freshwater Fish 18: 156–166. doi:10.1111/j.1600-0633.2008.00333.x.
  14. ↑ Barletta, M.; Jaureguizar, A.J.; Baigun, C.; Fontoura, N.F.; Agostinho, A.A.; Almeida-Val, V.M.F.; Val, A.L.; Torres, R.A.; Jimenes-Segura, L.F.; Giarrizzo, T.; Fabré, N.N.; Batista, V.S.; Lasso, C.; Taphorn, D.C.; Costa, M.F.; Chaves, P.T.; Vieria, J.P.; Corrêa, M.F.M. "Fish and aquatic habitat conservation in South America: A continental overview with an emphasis on Neotropical systems". Journal of Fish Biology 76: 2118–2176. doi:10.1111/j.1095-8649.2010.02684.x.
  15. ↑ 15.0 15.1 15.2 15.3 15.4 15.5 15.6 Iriarte, V.; Marmontel, M. (2013). "River Dolphin (Inia geoffrensis, Sotalia fluviatilis) Mortality Events Attributed to Artisanal Fisheries in the Western Brazilian Amazon". Aquatic Mammals 39 (2): 116–124. doi:10.1578/am.39.2.2013.116.
  16. ↑ Isaac, V.J.; Ruffino, M.L. (2007). "Evaluation of fisheries in Middle Amazon". American Fisheries Society Symposium 49: 587–596.
  17. ↑ Neiland, A.E.; Benê, C. (2008). Tropical River Fisheries Valuation:Background papers to a global synthesis. Penang, Malaysia: The World Fish Center. p. 290.
  18. ↑ Arraut, E.M., M. Marmontel, J.E. Mantovani, E.M. Novo, D.W. Macdonald, R.E. Kenward (2009). "The lesser of two evils: seasonal migrations of Amazonian manatees in the Western Amazon". Journal of Zoology 280 (3): 247–256. doi:10.1111/j.1469-7998.2009.00655.x.
  19. ↑ Reeves, R.R.; Smith, B.D.; Crespo, E.A.; Notarbartolo di Sciara, G. (2003). Dolphins, whales and porpoises: 2002-2010 conservation action plan for the world's cetaceans. Gland, Switzerland, and Cambridge, UK: International Union for Conservation of Nature/Species Survival Committee. p. 139.
  20. ↑ 20.0 20.1 Martin, A.R.; Da Silva, V.M.F.; Rothery, P. (2008). "Number, seasonal movements, and residency characteristics of river dolphins in an Amazonian floodplain lake system". Canadian Journal of Zoology 82: 1307–1315. doi:10.1139/z04-109.
  21. ↑ 21.0 21.1 Loch, C.; Marmontel, M.; Simões-Lopes, P.C. (2009). "Conflicts with fisheries and intentional killing of freshwater dolphins (Cetacea: Odontoceti) in the Western Brazilian Amazon". Biodiversity Conservation.
  22. ↑ Beltrán-Pedreros, S.; Filgueiras-Henriques, L.A. (2010). Biology, evolution and conservation of river dolphins within South America and Asia. New York: Nova Science Publishers Inc. pp. 237–246.
  23. ↑ 23.0 23.1 23.2 Crespo, E.A.; Alarcon, D.; Alonso, M.; Bazzalo, M.; Borobia, M.; Cremer, M.; Filla, G.F.; Lodi, L.; Magalhães, F.A.; Marigo, J.; Queiróz, H.L.; Reynolds, J.E. III; Schaeffer, Y.; Dorneles, P.R.; Lailson-Brito, J.; Wetzel, D.L. (2010b). "Report on the working group on major threats and conservation". The Latin American Journal of Aquatic Mammals 8 (1-2): 47–56. doi:10.5597/lajam00153.
  24. ↑ 24.0 24.1 Iriarte, V.; Marmontel, M. (2011). "Report of an encounter with a human intentionally entagled Amazon River dolphin (Inia geoffrensis) calf and its release in Tefé River, Amazonas State, Brazil". Uakari 7 (2): 47–56.
  25. ↑ 25.0 25.1 25.2 Alves, L.C.P.S.; Andriolo, A.; Zappes, C.A. (2012). "Conflicts between river dolphins (Cetacea:Odontoceti) and fisheries in the Central Amazon: A path toward tragedy?". Zoologia 29 (5): 420–429. doi:10.1590/s1984-46702012000500005.
  26. ↑ 26.0 26.1 Estupiñán, G.; Marmontel, M.; Queiroz, H.L.; Roberto e Souza, P.; Valsecchi, J.; da Silva Batista, G.; Barbosa Pereira, S. "A pesca da piracatinga (Calophysus macropterus) na Reserva de Desenvolvimiento Sustentável Mamirauá [The piracatinga fishery (Calophysus macropterus) at Mamirauá Sustainable Development Reserve].". Brazilian Ministry of Science and Technology. Retrieved 16 July 2014.
  27. ↑ Lodi, L.; Barreto, A. (1998). "Legal actions taken in Brazil for the conservation of cetaceans". Journal of International Wildlife Law and Policy I (3): 403–411. doi:10.1080/13880299809353910.
  28. ↑ 28.0 28.1 M. A. Cravalho (1999). "Shameless creatures: An ethnozoology of the Amazon river dolphin". Ethnology 38 (1): 47–58. doi:10.2307/3774086.
  29. ↑ Gravena, W., T. Hrbek, V.M.F. da Silva, and I.P. Farias (2008). "Amazon river dolphin love fetishes: From folklore to molecular forensics". Marine Mammal Science 24: 969–978. doi:10.1111/j.1748-7692.2008.00237.x.

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