ADW: Inia geoffrensis: INFORMATION

Geographic Range

Inia geoffrensis (boto or Amazon River dolphin) can be found in the Amazon and Orinoco river basins and their main tributaries in Bolivia, Brazil, Colombia, Ecuador, Peru, and Venezuela. Their distribution covers approximately 7 million square kilometers and is limited mainly by marine waters, impassable rapids, waterfalls, and excessively shallow parts of the rivers. Three subspecies are recognized, with each subspecies occupying a different area of these river systems: I. g. geoffrensis occupies the central Amazon River basin; I. g. humboldtiana resides in the Orinoco River basin; and I. g. boliviensis can be found in the upper Madeira River, cut off from the Amazon River by impassable rapids. The current distribution of this species does not appear to differ significantly from its estimated distribution in the past. (Best and da Silva, 1993; da Silva, 2002)

• Biogeographic Regions
• neotropical
  • native

Habitat

Within the aforementioned river systems, botos can be found in nearly all types of microhabitats, including in main rivers, small channels, mouths of rivers, lakes, and just below waterfalls and rapids. The water level cycle exerts the strongest influence on habitat use by these dolphins during different parts of the year, both directly, by determining which areas are navigable, and indirectly, by dictating where fish are most abundant. During the dry season, Inia geoffrensis is most abundant in the main river channels because smaller water channels are too shallow and prey items are concentrated along the margins of these rivers. During the wet season, botos can easily navigate smaller tributaries, and individuals even venture into river floodplains and flooded forests. Males and females appear to have different habitat preferences, with males returning to main river channels while water levels are still rising and females and their calves continuing farther inland. Females and calves may remain in the floodplains longer for several reasons. The calmer waters could prevent young botos from getting drawn away by strong river currents, allowing them to rest, nurse, and catch fish in a calmer environment. They may also be at a lower risk of aggression from adult males and predation from other species. (Best and da Silva, 1993; da Silva, 2002; Martin and da Silva, 2004)

• Habitat Regions
• tropical
• freshwater

• Aquatic Biomes

• lakes and ponds

• rivers and streams

• temporary pools

Economic Importance for Humans: Positive

There is little direct hunting of botos by native people, although Portuguese colonists may have hunted them to obtain oil for lamps. If botos are found dead, native people may use the fat as a cure for asthma and the oil to treat rheumatic pains or even infections in their cattle. They sometimes use the eyes, genitalia, and teeth as love charms and amulets as well. However, they never use the meat or skin. In addition, fishermen have been known to use botos to lead them to schools of fish. (Best and da Silva, 1989a; Best and da Silva, 1989b; Best and da Silva, 1993)

• Positive Impacts

• body parts are source of valuable material

• source of medicine or drug

Economic Importance for Humans: Negative

While there is little overlap between the fish that Inia geoffrensis prefers and the species that fisheries seek, botos have been known to tear fish from nets, causing damage to expensive fishing gear and, in some cases, a drastic reduction in fish catch. (Best and da Silva, 1989b; Culik, 2000)

Boto is the internationally-recognized common name of Inia geoffrensis, but other common names include the Amazon River dolphin, bufeo, bufeo colorado, tonina, delfin rosado, and pink dolphin. (da Silva, 2002)

Botos are part of the folklore of Amazonian people. There are several legends giving botos supernatural powers, which is why they are typically respected and protected. Some myths tell of botos turning into beautiful men or women during the night and luring members of the opposite sex down into the river, never to return. Another myth speaks of the spirits of drowned people entering the bodies of botos. (Best and da Silva, 1993; da Silva, 2002)

There is not consensus as to whether the ancestors of I. geoffrensis entered the Amazon River basin from the Pacific Ocean before the Andean orogeny 15 million years ago or from the Atlantic Ocean much more recently. (Best and da Silva, 1993)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Ryan Bebej (author), University of Michigan-Ann Arbor, Phil Myers (editor, instructor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

Neotropical

living in the southern part of the New World. In other words, Central and South America.

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

drug

a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease

echolocation

The process by which an animal locates itself with respect to other animals and objects by emitting sound waves and sensing the pattern of the reflected sound waves.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

freshwater

mainly lives in water that is not salty.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

migratory

makes seasonal movements between breeding and wintering grounds

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

piscivore

an animal that mainly eats fish

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

young precocial

young are relatively well-developed when born

References

2004. “Boto (Amazon River Dolphin), Inia geoffrensis fact sheet”
(On-line). American Cetacean Society.

Accessed
January 27, 2006
at http://www.acsonline.org/factpack/Boto.htm.

Best, R., V. da Silva. 1989. Amazon River Dolphin, Boto, Inia geoffrensis (de Blainville, 1817). Pp. 1-23 in S Ridgway, R Harrison, eds. Handbook of Marine Mammals: River Dolphins and the Larger Toothed Whales. London: Academic Press.

Best, R., V. da Silva. 1989. Biology, Status and Conservation of Inia geoffrensis in the Amazon and Orinoco River Basins. International Union for Conservation of Nature and Natural Resources (IUCN), Species Survival Commission, Occasional Paper 3: 22-34.

Best, R., V. da Silva. 1993. Inia geoffrensis. Mammalian Species, 426: 1-8.

Best, R., V. da Silva. 1984. Preliminary Analysis of Reproductive Parameters of the Boutu, Inia geoffrensis, and the Tucuxi, Sotalia fluviatilis, in the Amazon River System. Report of the International Whaling Commission, Special Issue 6: 361-369.

Brownell, R. 1984. Review of Reproduction in Platanistid Dolphins. Report of the International Whaling Commission, Special Issue 6: 149-158.

Caldwell, M., D. Caldwell, R. Brill. 1989. Inia geoffrensis in Captivity in the United States. International Union for Conservation of Nature and Natural Resources (IUCN), Species Survival Commission, Occasional Paper 3: 35-41.

Culik, B. 2000. “Inia geoffrensis (de Blainville, 1817)”
(On-line). Convention on Migratory Species.

Accessed
January 27, 2006
at http://www.cms.int/reports/small_cetaceans/data/I_geoffrensis/I_geoffrensis.htm.

Harrison, R., R. Brownell. 1971. The Gonads of the South American Dolphins, Inia geoffrensis, Pontoporia blainvillei, and Sotalia fluviatilis
. Journal of Mammalogy, 52: 413-419.

Martin, A., V. da Silva. 2004. River dolphins and flooded forest: seasonal habitat use and sexual segregation of botos (Inia geoffrensis) in an extreme cetacean environment. Journal of the Zoological Society of London, 263: 295-305.

Martin, A., V. da Silva. 2006. Sexual dimorphism and body scarring in the boto (Amazon River dolphin) Inia geoffrensis
. Marine Mammal Science, 22: 25-33.

McGuire, T., K. Winemiller. 1998. Occurrence Patterns, Habitat Associations, and Potential Prey of the River Dolphin, Inia geoffrensis, in the Cinaruco River, Venezuela. Biotropica, 30: 625-638.

Vidal, O. 1993. Aquatic Mammal Conservation in Latin America: Problems and Perspectives. Conservation Biology, 7: 788-795.

da Silva, V. 2002. Amazon River Dolphin. Pp. 18-20 in W Perrin, B Würsig, J Thewissen, eds. Encyclopedia of Marine Mammals. San Diego: Academic Press.