AS-HOPE report

Number:AS-22-016

Study on Acoustic behavior of South American wild dolphins.

Report:Yoshida Yayoi

Date:2010/06/04 - 2010/06/20

In order to study acoustic behavior of dolphins in Amazon River, we visited National Institute for Amazon Research (INPA) for the meeting with our co-researcher, Dr. Vera da Silva. After the meeting we visited a tributary of Rio Negro river approximately 60km from Manaus, one of the possible study sites of Amazon River dolphin (Boto; Inia geoffrensis) and Tucuxi (Sotalia fluviatilis) for preliminary investigation and recording. The study site was a small tributary of approximately 500m in length and about 10 m in width. Group size of botos identified in our direct observation there ranged from 1 to 6 individuals. We recorded the sounds (whistles and pulses) of boto for 240 min in total during 2 days. Their whistle sound, the sound known as communication sounds in many dolphin species, increased tendency to be recorded just after the boats passed the study site. It is possible that we recorded not only the sounds of boto but also those of tucuxi because we sometime observed tucuxies in the sites. We will examine this possibility by further analysis. Based on these preliminary results, we will start our main field research in the end of this year. After the visit to Brazilian Amazon, we visited the Scientific Research Center of Chile (CECS) in Valdivia, Chile, to see co-researchers for the study of dolphins inhabiting Chilean coasts. We tried to visit possible study sites by boats but could not do it because of bad sea condition. However, we could see co-researchers, Prof. Rodrigo Hucke-Gaete and Dr. Franscisco Viddi, and make fruitful discussion on the field operation in the main field research at the end of this year.

amazon river dolphin


amazon river dolphin

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