Bolivian Amazon Dolphin
| Bolivian Amazon Dolphin | ||||||||||||
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The Bolivian Amazon Dolphin (drawing by d'Orbigny, 1847) |
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| Inia boliviensis | ||||||||||||
| d'Orbigny , 1834 |
The Bolivian Amazon Dolphin ( Inia boliviensis , Syn .: Inia geoffrensis boliviensis ) is a species of Amazon river dolphins that occurs in the upper reaches of the Rio Madeira in Bolivia and in southwestern Brazil . The dolphin, formerly regarded as a subspecies of the Amazon dolphin ( Inia geoffrensis ), was confirmed as an independent species in 2008 by molecular biological studies.
features
The Bolivian Amazon dolphin corresponds in appearance and body size to the Amazon dolphin ( Inia geoffrensis ), as the subspecies of which it has long been considered, and the Araguaia dolphin ( Inia araguaiaensis ). Measurements of the animals are rare and there are only two official figures of body lengths of two females, which were 208 and 216 centimeters long. A sexual dimorphism occurs within the genus , the males are usually larger and more powerfully built; this is also assumed for the Bolivian Amazon dolphin. The skull of the Bolivian Amazon dolphin contains 31 to 34 teeth per half of the lower jaw and thus more than that of the other two species (24–28 in Inia araguaiaensis and 25–29 in I. geoffrensis ), the upper jaw contains 31 to 35 teeth. 9 to 11 of the teeth in the upper and lower jaw are molar- like. The skull is also built narrower, with a length of about 73% of the total length of the skull , the rostrum is longer than I. geoffrensis , where it is about 65% of the total length of the skull.
distribution
The Bolivian Amazon Dolphin is only found in the upper reaches of the Rio Madeira and associated river systems in northern Bolivia and southwest Brazil. The distribution area is in the Bolivian lowlands north of the Chiquitanía . In addition to the Rio Madeira, the Río Beni , the Río Ichilo , the Río Mamoré , the Río Ipurupuru , the Río Ibare , the Río Baré , the Río Abuná and the Río Iténez also belong to the range of the animals.
Way of life
The Bolivian Amazon Dolphin lives in sediment-rich rivers, lakes and floodplain areas of the plains, whereby it prefers areas with clear water. Like the other species of the genus, the animals mainly gather at confluences, but are in principle present in all available habitats .
There is very limited or no information available about the species' way of life, but it is likely to be essentially the same as that of the Amazon dolphin. Like the latter, the Bolivian Amazon dolphin feeds primarily on fish. The mating season and births probably take place throughout the year, with more young animals being born, especially in shallow water times.
Systematics
The Bolivian Amazon dolphin was first described in 1834 by the French naturalist Alcide Dessalines d'Orbigny from the Río Iténez in Bolivia. In 2008 it was confirmed as an independent species with the help of molecular biological methods.
Together with the Amazon dolphin ( Inia geoffrensis ) and the Araguaia dolphin ( Inia araguaiaensis ), which was only described in 2014, it forms the genus Inia , the only genus of the Amazon river dolphins (Iniidae). Within this the Araguaia dolphin is the sister species of the Amazon dolphin and has from that during the Gelasian about 2 million years ago separated , as the basin of the Rio Araguaia and Tocantins from the Amazon basin was cut off. The sister group of this clade is the Bolivian Amazon Dolphin. It was isolated about 2.9 million years ago by the Teotonio rapids in the upper Rio Madeira region .
Hazard and protection
As with the other species of river dolphins, very little data on the populations and stocks of the Bolivian Amazon dolphin is available. The International Union for Conservation of Nature and Natural Resources (IUCN) has so far not considered the species to be in its own right, but as a subspecies of the Amazon dolphin and classified as “data deficient” based on the data available. Estimates assume a total population of around 1400 to 4000 individuals and a density of 3.2 to 3.5 individuals per river kilometer in the distribution area.
Although the populations of the Bolivian Amazon dolphin are separated from those of the Amazon dolphin by rapids and other barriers, individual animals regularly crossed the barriers, especially during floods. With the construction of the Jirau dam and the Santo Antônio dam on the Rio Madeira from 2008 to 2013, the habitats are now completely separated. In Bolivia, the species is indirectly protected in the Political Constritution of Supreme Decree 25458 of July 1999, which prohibits hunting and trading in species of the national fauna that are believed to be endangered. In 2008, a law was passed in Beni Department declaring the Bolivian Amazon dolphins a natural heritage.
supporting documents
- ↑ a b c d e f V.MF da Silva, AR Martin: Family Iniidae (Amazon River Dolphins); Bolivian Boto Inia boliviensis In: Don E. Wilson, Russell A. Mittermeier: Handbook of the Mammals of the World. 4. Sea Mammals. Lynx Edicions, Barcelona 2014; P. 378. ISBN 978-84-96553-93-4 .
- ↑ M. Ruiz-García, S. Caballero, M. Martinez-Agüero, JM Shostell JM: Molecular differentiation among Inia geoffrensis and Inia boliviensis (Iniidae, Cetacea) by means of nuclear intron sequences. In: VT Koven (editor): Population Genetics Research Progress. Boca Raton, Nova Publishers 2008; Pp. 177-203.
- ↑ Tomas Hrbek, Vera Maria Ferreira Da Silva, Nicole Dutra, Waleska Gravena, Anthony R. Martin, Izeni Pires Farias: A New Species of River Dolphin from Brazil or: How Little Do We Know Our Biodiversity. In Samuel T. Turvey, PLoS ONE 9, 2014: e83623. doi: 10.1371 / journal.pone.0083623 .
- ↑ Inia geoffrensis in the IUCN Red List of Threatened Species 2015.4. Submitted by: AV Linzey, NatureServe (G. Hammerson), 2008. Retrieved July 3, 2016.
literature
- VMF da Silva, AR Martin: Family Iniidae (Amazon River Dolphins); Bolivian Boto Inia boliviensis In: Don E. Wilson, Russell A. Mittermeier: Handbook of the Mammals of the World. 4. Sea Mammals. Lynx Edicions, Barcelona 2014; P. 378. ISBN 978-84-96553-93-4 .
- M. Ruiz-García, S. Caballero, M. Martinez-Agüero, JM Shostell JM: Molecular differentiation among Inia geoffrensis and Inia boliviensis (Iniidae, Cetacea) by means of nuclear intron sequences. In: VT Koven (editor): Population Genetics Research Progress. Boca Raton, Nova Publishers 2008; Pp. 177-203.
Web links
- Inia geoffrensis inthe IUCN Red List of Threatened Species 2015.4. Submitted by: AV Linzey, NatureServe (G. Hammerson), 2008. Retrieved July 3, 2016.