In The Hitchiker's Guide to the Galaxy, Douglas Adams noted that "On the planet Earth, man had always assumed that he was more intelligent than dolphins because he had achieved so much - the wheel, New York, wars and so on - whilst all the dolphins had ever done was muck about in the water having a good time. But conversely, the dolphins had always believed that they were far more intelligent than man - for precisely the same reasons. The last ever dolphin message was misinterpreted as a surprisingly sophisticated attempt to do a double-backwards-somersault through a hoop whilst whistling the 'Star Spangled Banner', but in fact the message was this: So long and thanks for all the fish."
Following on Adams, Carl Sagan brilliantly observed that, "It is of interest to note that while some dolphins are reported to have learned English – up to 50 words used in correct context – no human being has been reported to have learned dolphinese."
"Carl Sagan was right!" said Lori Marino, a biopsychologist from Emory University in Atlanta, Georgia. "We still don't understand the natural language system of dolphins and whales. We know a little bit more now, and there have been investigators working on this for decades, but we haven't really cracked the code."
The scientific community had thought that whistles were the main means to communicate , and were unaware of the importance and use of burst-pulsed sounds. Researchers from the Bottlenose Dolphin Research Institute (BDRI), based in Sardinia (Italy) have now shown that these sounds are vital to the animals' social life and mirror their behavior.
Although lacking vocal cords, dolphins emply the sphincter muscles within the blow holes to communicate by producing a complicated system of whistles, squeaks, moans, trills and clicks of varying frequencies. The clicks are also a device for echolocation, or sonar, the clicking sounds bouncing off objects with the echoing sound waves sensed by the dolphin's bulbous forehead and lower jaw. These communicative mechanisms enables them to determine the distance, size and shape of objects.
"Burst-pulsed sounds are used in the life of bottlenose dolphins to socialise and maintain their position in the social hierarchy in order to prevent physical conflict, and this also represents a significant energy saving," says Bruno Díaz, lead author of the study and a researcher at the BDRI.
The study presents the most complete repertoire ever of these burst-pulsed sounds and whistles, gathered using bioacoustics since 2005 in the waters off Sardinia.
According to the experts, the tonal whistle sounds (the most melodious ones) allow dolphins to stay in contact with each other (above all mothers and offspring), and to coordinate hunting strategies. The burst-pulsed sounds (which are more complex and varied than the whistles) are used "to avoid physical aggression in situations of high excitement, such as when they are competing for the same piece of food, for example," explains Díaz.
Bottlenose dolphins, according to Díaz, make longer burst-pulsed sounds when they are hunting and at times of high aggression: "These are what can be heard best and over the longest period of time," and make it possible for each individual to maintain its position in the hierarchy.
The dolphins emit these strident sounds when in the presence of other individuals moving towards the same prey. The "least dominant" one soon moves away in order to avoid confrontation. "The surprising thing about these sounds is that they have a high level of uni-directionality, unlike human sounds. One dolphin can send a sound to another that it sees as a competitor, and this one clearly knows it is being addressed," explains the Spanish scientist.
A possible takeawy from the current state of reserach on Dolphin intelligence is that the universe may be full of social, intelligent life, but the level and type of intelligence it takes to create sophisticated technology may be rare indeed.
The Daily Galaxy via Phys.org and Plataforma SINC (2010, June 9) and http://www.space.com/12811-dolphin-intelligence-search-extraterrestrial-life.html