AEAS阅读训练 – River Dolphins Have a Wide Vocal Repertoire

River Dolphins Have a Wide Vocal Repertoire

Freshwater dolphins live in many of the world’s biggest rivers, from the Amazon to the Ganges, and they differ in many ways from their better-known oceangoing cousins. “They have a flexible neck. They have different types of teeth. They can also move their flippers independently in different directions, so they can swim backwards.”

Gabriel Melo-Santos, a marine biologist at the University of St. Andrews in Scotland. “When I decided I was going to be a biologist I decided I wanted to study dolphins. And being born in the Amazon, it was only natural to go for the river dolphins.”

He says another thing that sets his study subjects apart from marine dolphins are their calls .

Over several years, Melo-Santos has recorded the sounds of Araguaian river dolphins that came calling at the Mocajuba fish market. That’s on Brazil’s Tocantins River. Using sound analysis software, his team fished 237 distinct sound types from the recordings—indicating the dolphins have a wide repertoire.

River Dolphins Have a Wide Vocal Repertoire

The call collection, published in the journal PeerJ, has only a few whistles. Instead, three quarters of the collected sounds were short two-parters, like this one produced by a female calf as she rubbed her head on her mother’s belly. It’s a call that’s more similar in structure to the ones orcas and pilot whales make to identify a family or social group than to the social whistles of marine dolphins.

“These are older lineages, right? So if you understand how these dolphins communicate, we might have a sense to understand how the communication system evolved in different lineages of cetaceans.” Meaning perhaps these calls between mother and calf are, like the river dolphins themselves, an evolutionary relic.

河豚声域更广

淡水海豚生活在世界上许多最大的河流中,从亚马逊河到恒河,它们在许多方面不同于更为人所知的远洋近亲。“它们的脖子很灵活。有不同类型的牙齿。它们还可以向不同的方向独立移动鳍状肢,这样就可以向后游了。”

加布里埃尔·梅洛-桑托斯(Gabriel Melo-Santos)是苏格兰圣安德鲁斯大学的海洋生物学家。“当我决定要成为一名生物学家时,决定要研究海豚。由于出生在亚马逊河流域,所以河豚是很自然的选择。”

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他说,他的研究对象与海洋海豚的另一个区别是它们的叫声。

几年来,梅洛-桑托斯记录了阿拉瓜湾河豚在莫卡朱巴鱼市的叫声。那是在巴西的托坎廷斯河上。通过使用声音分析软件,他的团队从记录中提取了237种不同的声音类型——这表明河豚拥有广泛的技能。

河豚有广泛的发声能力

收集的声音样本,只有几种叫声,发表在《PeerJ》杂志上。相反,收集到的声音中有四分之三是短的两拍子声音,就像这只母牛犊用头在妈妈肚子上摩擦时发出的声音。这种叫声在结构上更类似于虎鲸和领航鲸识别一个家庭或社会群体的叫声,而不是河豚发出的社会哨声。

这些是更古老的血统,对吧?所以,如果你了解了这些河豚是如何交流的,我们或许就能理解在鲸类动物的不同谱系中,交流系统是如何进化的。”这意味着,也许这些母河豚和幼海豚之间的叫声,就像河豚本身一样,是进化的遗迹。