Dolphins beaching, still a mystery to experts.

Dozens of bottle-nosed dolphins have died after beaching themselves on a remote Mozambique coastline, mystifying environmentalists who say mass beachings are very rare in the area."It's very unusual but even when one or two are beached you very rarely find the cause of death," Peter Best of the mammal research institute at the University of Pretoria said on Monday.

Witnesses said 47 dolphins came onshore on Bazaruto Island off mainland Mozambique early on Saturday. Rescuers managed to return six of them to the water.Scientists do not know why large groups of dolphins or whales occasionally beach themselves in different parts of the world.Nick Raba, a member of Eyes on the Horizon, a group of citizens who help police fishery laws in the area, was one of the first people to arrive at the scene."There wasn't a marking on them, no signs of disease, and not fishing nets wrapped around them. Something very strange has gone wrong," he said.

"This is quite a shock."About 21 whales and dolphins have been reported to have beached themselves this year in South Africa.