Araguaian botos (Inia araguaiaensis) are known to produce pulsed as well as tonal sounds. This study documents the first evidence for repetitive sequences of downsweep whistles in botos that appear to be shared between individuals, and the context of their occurrence is investigated. Boat surveys were conducted along the Tocantins River located in the Eastern Amazon over a period of 42 days between 2012 and 2018. Eighty-two groups of Araguaian botos were observed, and 43 h of sound recordings were acquired. 632 downsweep whistles were recorded in 10 encounters. Four of these encounters contained downsweep bouts (21 bouts with ≥2 whistles) with short inter-call intervals (bout criterion 50 s) and up to 161 whistles. A statistical relationship was not found between downsweep occurrence and any of the contextual parameters that were investigated, including socializing, travelling, feeding, group size, presence of calves, and socio-sexual displays. The rarity of these signals makes them unlikely candidates for individual or group identification. It is more likely that they are associated with very specific contexts, such as nursing or mating, both of which were rarely observed in this study. Further studies are required to investigate context specificity and elucidate the function of these signals.
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February 2020
February 05 2020
Repeated downsweep vocalizations of the Araguaian river dolphin, Inia araguaiaensis
Gabriel Melo-Santos;
Gabriel Melo-Santos
a)
1
Sea Mammal Research Unit, Scottish Oceans Institute, School of Biology, University of St Andrews
, East Sands, KY16 8LB, St Andrews, Scotland, United Kingdom
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Sam F. Walmsley;
Sam F. Walmsley
1
Sea Mammal Research Unit, Scottish Oceans Institute, School of Biology, University of St Andrews
, East Sands, KY16 8LB, St Andrews, Scotland, United Kingdom
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Miriam Marmontel;
Miriam Marmontel
2
Research Group on Amazonian Aquatic Mammals, Mamirauá Sustainable, Development Institute
, Estrada do Bexiga No. 2584, Tefé, Brazil
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Marcelo Oliveira-da-Costa;
Marcelo Oliveira-da-Costa
3
WWF Brazil (World Wide Fund for Nature)
, Brasília, Federal District, Brazil
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Vincent M. Janik
Vincent M. Janik
1
Sea Mammal Research Unit, Scottish Oceans Institute, School of Biology, University of St Andrews
, East Sands, KY16 8LB, St Andrews, Scotland, United Kingdom
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a)
Also at: BioMA—Biology and Conservation of Amazonian Aquatic Mammals, Belém, Brazil. Electronic mail: gmads@st-andrews.ac.uk
J. Acoust. Soc. Am. 147, 748–756 (2020)
Article history
Received:
August 12 2019
Accepted:
January 09 2020
Citation
Gabriel Melo-Santos, Sam F. Walmsley, Miriam Marmontel, Marcelo Oliveira-da-Costa, Vincent M. Janik; Repeated downsweep vocalizations of the Araguaian river dolphin, Inia araguaiaensis. J. Acoust. Soc. Am. 1 February 2020; 147 (2): 748–756. https://doi.org/10.1121/10.0000624
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