Listen to dolphins whistling to each other and you could be forgiven for thinking that they are having a conversation. Now we鈥檙e a bit nearer to understanding what they might be saying, thanks to a project that has distinguished nearly 200 different whistles dolphins make and linked some of them to specific behaviours.
Liz Hawkins of the Whale Research Centre at Southern Cross University in Lismore, New South Wales, Australia, eavesdropped on bottlenose dolphins living off the eastern coast of Australia for her three-year study.
鈥淭his communication is highly complex, and it is contextual, so in a sense, it could be termed a language,鈥� says Hawkins, who presented her work at a meeting of the Society for Marine Mammalogy in Cape Town, South Africa, this month.
Advertisement
Dolphins were known to use 鈥渟ignature鈥� whistles to identify themselves to others, but the meaning of the other whistles they make was a mystery.
Hawkins recorded a total of 1647 whistles from 51 different pods of dolphins living in Byron Bay, New South Wales. From the starting frequency of the sound, its duration, and its end frequency, she identified 186 different whistle types. Of these, 20 were especially common.
Hawkins grouped all the whistles into five tonal classes and found that these groups, and even individual whistles, clearly went with different behaviours. When a pod was travelling, for instance, 57 per cent of the whistles were 鈥渟ine鈥� whistles, rising and falling symmetrically. But when the dolphins were feeding or resting, they made far fewer whistles of this type. And while socialising, they communicated almost exclusively using flat-toned or rising-toned whistles.
The dolphins often made a particular flat-toned whistle when they rode the waves created by Hawkins鈥檚 boat, and it鈥檚 tempting to speculate that the whistle is the equivalent of a child going 鈥渨heeee!鈥�. And in a group of dolphins living off Moreton Island in Queensland, Hawkins identified a whistle often emitted by an animal when it was on its own. 鈥淭hat whistle could definitely mean: 鈥業鈥檓 here, where is everyone?'鈥� says Hawkins.
Melinda Rekdahl, of the University of Queensland in Brisbane, is also investigating dolphin whistles. She found they make more whistles when they鈥檙e being hand-fed than dolphins feeding in the wild. It鈥檚 too early to know whether whistles might mean something as specific as 鈥渉urry up鈥� or 鈥渢here鈥檚 food over here,鈥� Rekdahl says. 鈥淏ut it鈥檚 possible. Dolphin communication is much more complicated than we thought.鈥�
