A dolphin washed ashore on Grand Isle and was discovered Friday morning, Mayor David Camardelle said. It was the second large marine mammal found on the town's beaches in less than a month.

The animal is believed to be a Risso's dolphin and is about 9 feet long, said Trey Isles, a spokesman for the Louisiana Department of Wildlife and Fisheries. Risso's dolphins are found in tropical to warm temperate waters around the world, including the northern Gulf of Mexico, Iles said.

A field necropsy will be conducted on the dolphin Saturday or Sunday, he said.

The dolphin was much smaller than a juvenile sperm whale that washed ashore on Grand Isle last month, Iles said. The cause of the whale's death has not been determined and may never be known, he said.

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