Saturday, May 27, 2006

Identification Among Dolphins: They're Smarter Than the Average Mammal

by Elizabeth Bauman (Class of '06)

Scientists have recently found that dolphins communicate using names. Through the dolphin’s whistle and the dolphin’s voice, dolphins can identify each other and interact verbally. This new discovery makes bottlenosed dolphins, like the one who starred in the famous movie “Flipper,” the only known, non-human animal besides the spectacled parrotlets that have the ability to address one another by an individualized name.

The research was led by Vincent Janik of the University of St. Andrews in Scotland, and it tested the differences in response of the dolphins between a dolphin’s whistle and a dolphin’s “voice.” The scientists recorded the dolphin’s whistles, stripped them of the intonation and sound that would identity the dolphin’s “voice,” and replayed the whistle through an underwater speaker to observe the responses of the dolphins. The scientists found that close relatives of the dolphin would react strongly to the whistle, while many unrelated dolphins would also react to the whistle, indicating that the dolphin’s whistle, regardless of its voice, does provide a means of identification for the dolphin.

The researchers found that dolphins develop their signature whistle as infants and use their personal whistle throughout their lifetimes. Other dolphins repeat the specific whistle back, which shows that they are calling the dolphin by its individual name. In addition, since each dolphin’s blowhole creates a unique and distinct sound, dolphins are able to recognize each other’s voices. Voices are distorted by water pressure, however, so personal whistles are another conclusive means of identification.

Dr. Janik reported from his research, "Bottlenose dolphins are the only animals other than humans to have been shown to transmit identity information independent of the caller's voice."

The interest in dolphin voice recognition began in the 1960’s when researchers noticed a specific set of whistles among captured dolphins. The theory of communication among dolphins was controversial for years and was only recently tested and proven correct. While it is clear that dolphins communicate through personal voice and identifying whistles, scientists are unsure if communication between dolphins can be considered language.

"Language by the standard definition must have syntax-or structuring of words- and reference," said Dr. Laela Sayigh, an investigator at the Woods Hole Oceanographic Institution and the co-leader of the study. "Dolphins do have the ability to use artificial signals to refer to objects, but it is unclear at present if their vocalizations involve syntax."

Scientists are also unclear if dolphins have different accents and dialects in different regions of the world, which could be identified through different patterns and frequencies of the whistles.

"Dolphins in Australia do seem to produce more simple whistles, while Florida dolphin whistles appear to be more modulated," Sayigh said. "Right now, we don’t know why that happens."

The research on communication between animals is continuous and productive. The recent evidence about dolphin voice and name recognition sheds new light on animal interactions. Dolphins’ brains have evolved to an almost human level of intelligence.


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