September 30, 2010

Scientist Finds Two Dolphin Species Using ‘Common Language’

Two distantly related species of dolphin -- the Guyana and the Bottlenose -- often can be found socializing in waters off the coast of Costa Rica, according to a recent BBC report.

Both species of dolphin make distinct sounds, but when they meet up, they change the way they communicate with each other by using a transitional language. It raises possibilities that the two species are communicating in some way.

Details of the finding are published in the journal Ethology.

It is not clear to scientists exactly what is going on between the two species, but it is the first evidence that the marine mammals modify their communication skills in the presence of other species, not just other dolphins of their own kind.

The amazing discovery was made by biologist Dr Laura May-Collado of the University of Puerto Rico in San Juan while studying dolphins swimming in the Gandoca-Manzanillo Wildlife Refuge off the southern coast of Costa Rica.

Both species of dolphin normally swim in groups made up of their own kind.

When bottlenose dolphins swim together, they emit long, lower frequency calls that are modulated. Guyana dolphins usually communicate using higher frequencies that have their own particular structure.

But often, the two species join together and swim in one group. The interactions are usually aggressive, as the larger bottlenose dolphins -- 12.5 feet long compared to the 7-foot long Guyanas -- harass their smaller counterparts.

When the two dolphin species are together, they produce quite different calls, May-Collado found.

During these multi-species gatherings, their calls are of a more intermediate frequency and duration. In other words, the dolphins start communicating in a style that is somewhere between the normal call range for both species.

"I was surprised by these findings, as I was expecting both species to emphasize, perhaps exaggerate, their species-specific signals," May-Collado told BBC. "Instead the signals recorded during these encounters became more homogenous."

However, she said she could not be sure if both species are changing the way they communicate, or whether it is one species trying to call more like the other.

That is because the sound equipment used could only record the total calls produced by mixed species groups of dolphins, and could not separate the sounds made by both dolphin species.

May-Collado said that limits "how much I can say about how much they are communicating."

However, dolphins have the remarkable ability to change their calls when "Ëœtalking' to other individuals, or to ensure they are heard over any background noise pollution.

"I wouldn't be surprised that they can modify their signals to mimic, and even possibly communicate with other species. Particularly when their home ranges force them to interact on a daily basis, which is the case of this study," she said.

It is also not clear whether the two dolphins are just trying to learn to communicate using a common language, or whether the Guyanas are making the sounds alone due to stress. Or it could even be that the Guyana dolphins are attempting "to emit threatening sounds in the language of the intruder," trying to get the bottlenoses to abstain from their harassing behavior, Dr May-Collado added.


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