Bolivian river dolphin site preference in the middle-section of mamoré river, upper madeira river basin, Bolivia

Enzo Aliaga-Rossel, Luis A.Guizada Duran

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


The South American river dolphins of genus Inia are distributed throughout the Amazon, Orinoco and Araguaia-Tocantins basins. They are categorized as Endangered and the knowledge on their basic ecology is still scarce. Therefore, investigation efforts must contribute to the knowledge and conservation of these species in their area of distribution. For the Bolivian river dolphin we used a database of 10 years of upstream and downstream surveys, accumulating approximately 6,100 km of double routes from three main rivers of the Upper Madeira River basin (Ibare, Mamoré and Tijamuchi) by following standardized methods where each encounter with a single or a group of river dolphins was registered. Preferred sites by Bolivian river dolphin were based on Kernel density estimation. This methodology considers the accumulated data of georeferenced sightings, generating a map of probability of occurrence in each river. In the three rivers, the accumulated density of sightings is concentrated in meanders and confluences, resulting in a high probability of sighting Bolivian river dolphin in these habitats. It was also identified that the number of Bolivian river dolphin sightings decreased over time in the upper Tijamuchi River. The Bolivian river dolphin preferred both meanders and confluence habitats. Between the Ibare and Tijamuchi rivers (Mamoré sub-basin), the distribution of the species tended to be more uniform. According to these results, it is important to reinforce the management of the Ibare-Mamoré municipal protected area, since important Bolivian river dolphin populations are concentrated there. Same trend was also shown in the lower-middle zone of the Tijamuchi River, suggesting the need of implementing conservation strategies in this area, where currently there are none. Los delfines de río sudamericanos del género Inia se distribuyen por las cuencas del Amazonas, Orinoco y Araguaia-Tocantins, se clasifican como en peligro de extinción y el conocimiento sobre su ecología básica aún es escaso. Por lo tanto, las investigaciones deben contribuir a la conservación y el conocimiento de estas especies en su área de distribución. Para el delfín del río boliviano, utilizamos una base de datos de 10 años de recorridos río aguas-arriba y río aguas-abajo, acumulando aproximadamente 6,100 km de rutas dobles en tres ríos principales en la subcuenca alta del río Madeira (Ibare, Mamoré y Tijamuchi). Siguiendo los métodos estandarizados cada encuentro con uno o un grupo de delfines de río fue registrado. La identificación de los sitios preferidos por los bufeos fue estimada por la densidad del Kernel. Esta metodología considera los datos acumulados de avistamientos georreferenciados que generan un mapa de probabilidad de ocurrencia en cada río. En los tres ríos, la densidad acumulada de avistamientos se concentra en meandros y confluencias, lo que resulta en una alta probabilidad de ver bufeos en estos hábitats. También se determinó que los avistamientos de bufeos han disminuido en la parte superior del río Tijamuchi. Los bufeos prefirieron los hábitats de meandros y de confluencia; entre los ríos Ibare y Tijamuchi (cuenca Mamoré), la distribución de las especies tendió a ser más uniforme. Según estos resultados, es importante reforzar la gestión del área protegida municipal de Ibare-Mamoré, ya que allí se concentran importantes poblaciones de bufeo. La misma tendencia también se mostró en la zona media-baja del río Tijamuchi, lo que sugiere la necesidad de implementar estrategias de conservación en esta área, donde actualmente todavía no se ha declarado ninguna.

Original languageEnglish
Pages (from-to)459-465
Number of pages7
Issue number3
StatePublished - 2020

Bibliographical note

Funding Information:
We dedicate this paper to the memory of Sydney Anderson. As a junior undergraduate EAR had the fortune of participating of a field trip with the Anderson-Yates expedition. Years later, EAR received a letter from Dr. Anderson – which made a world of difference in his career path --encouraging him to follow his passion and interest to study bufeos. We also thank J. Salazar-Bravo for his invitation to contribute to this special issue. We thank the Whale and Dolphin Conservation (WDC), Rufford Foundation, and International Foundation for Science (IFS) for the support to Bolivian river dolphin conservation. Thanks to the field assistants in each survey, as well as our gratitude to our outboard motor divers. Special thanks to D. Salas Veizaga for the English review. Earlier versions of this manuscript were improved thanks to the insightful reviews by M. Marmontel (Mami-rauá Institute for Sustainable Development, Tefé, Brazil) and an anonymous reviewer.

Publisher Copyright:
© 2020 Asociación Mexicana de Mastozoología.


  • Bufeo
  • Conservation area
  • Kernel density
  • Occurrence probability
  • Preferred pites


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