Sea Mammal Research Unit, Scottish Oceans Institute, School of Biology, University of St Andrews, East Sands, KY16 8LB, St Andrews, Scotland, United Kingdom.
Research Group on Amazonian Aquatic Mammals, Mamirauá Sustainable, Development Institute, Estrada do Bexiga No. 2584, Tefé, Brazil.
J Acoust Soc Am. 2020 Feb;147(2):748. doi: 10.1121/10.0000624.
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.
阿拉瓜亚河豚（Inia araguaiaensis）已知会发出脉冲声和音调声。本研究记录了首例在河豚中出现的、似乎在个体之间共享的下扫口哨重复序列的证据，并调查了它们出现的背景。2012 年至 2018 年期间，在亚马逊东部的托坎廷斯河上进行了为期 42 天的船只调查。共观察到 82 组阿拉瓜亚河豚，采集了 43 小时的录音。在 10 次相遇中记录到 632 次下扫口哨声。其中 4 次相遇包含下扫爆发（21 次爆发包含≥2 次口哨声），其呼叫间隔较短（爆发标准为 50 秒），且口哨声多达 161 次。下扫发生的频率与我们研究中调查的任何背景参数都没有统计学关系，包括社交、游动、觅食、群体大小、幼豚的存在和社会性行为展示。这些信号很罕见，不太可能用于个体或群体识别。它们更可能与非常特定的背景相关，例如哺乳或交配，而这两种情况在本研究中都很少观察到。需要进一步的研究来调查这些信号的具体背景和功能。
