Environment

Researchers Say Dolphin Attacks Behind Mass Deaths Of Porpoises

by Yuliya Talmazan | November 9, 2009 at 10:26 am

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Researchers are suggesting dolphin attacks are likely behind the sudden spike in the number of deaths of porpoises off the coast of California. Over 70 porpoises have washed out bloody and injured on the beaches of California last year. But, scientists were puzzled as to the reason behind the phenomenon.

A new video shot by researchers from the conservation group Okeanis shows a group of dolphins attacking a lone porpoise, beating and drowning it to death. Moreover, dolphins in the video deliver the carcass of the porpoise onto the researchers' boat and swim away. The video was not made available to view by Okeanis, however.

Dolphins are known as peaceful animals, but scientists say all sorts of interactions can occur in the wild. Although the reason behind the attacks is unclear, researchers are speculating that high levels of testosterone might be to blame. The dolphins that participated in the porpoise beating in the video were all allegedly male. The elevated aggressiveness levels seen in male dolphins might have to do with the lack of female dolphins in the area. But, there are other reasons that researchers are looking into.

“Now we know the how, but we still are unsure of the why,” said Daniela Maldini, president of the Okeanis board. “We have been observing the social structure of these animals and it has taken us 20 years to do that. This type of behavior is something new.”

“It was incredible to finally fit some action to our theories,” said Okeanis field director Mark Cotter, who captured the footage along with fellow researcher Thomas Jefferson. “It diminishes the image of the bottlenose dolphin in a way that wild animals are not like those you see at SeaWorld. They all have their own individual personalities.”