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Scientists study hundreds of dead dolphinsScientists study hundreds of dead dolphins
Scientists tried to discover on Saturday why hundreds of dolphins washed up dead on a beach popular with tourists on the northern coast of Zanzibar.
Among other possibilities, marine biologists were examining whether US Navy sonar threw the animals off course.
Villagers and fishermen were burying the remains of the roughly 400 bottlenose dolphins, which normally live in deep offshore waters but washed up on Friday along a 4-kilometre stretch of coast in Tanzania's Indian Ocean archipelago.
The animals may have been disturbed by some unknown factor, or poisoned, before they became stranded in shallow waters and died, said Narriman Jiddawi, a marine biologist at the Institute of Marine Science of the University of Dar es Salaam.
Experts planned to examine the dolphins' heads to assess whether they had been affected by military sonar.
Some scientists surmise that loud bursts of sonar, which can be heard for kilometres in the water, may disorient or scare marine mammals, causing them to surface too quickly and suffer the equivalent of what divers call the bends when sudden decompression forms nitrogen bubbles in tissue.
A US Navy task force patrols the coast of East Africa as part of counterterrorism operations. A Navy official was not immediately available for comment, but the service rarely speaks about the location of submarines at sea.
A preliminary examination of their dolphins' stomach contents failed to show the presence of squid beaks or other remains of animals hunted by dolphins.
That was an indication that the dolphins either had not eaten for a long time or had vomited, Jiddawi said.
Their general condition, however, appeared to show that they had eaten recently, since their ribs were not clearly visible under the skin, she said.
Although Jiddawi said on Friday that poisoning had been ruled out, experts were preparing to further examine the dolphins' stomachs for traces of poisonous substances such as toxic "red tides" of algae.
Zanzibar's resorts attract many visitors who come to watch and swim with wild humpback dolphins, which generally swim closer to shore than the Indo-Pacific bottlenose.
Source: China Daily
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