Over the past week, 512 penguins have washed up dead on the shores of the Rio Grande do Sul state in southern Brazil. Marine biologists and veterinarians are working together to investigate, performing autopsies to determine the cause of the mysterious deaths.
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But so far, details remain hazy. The penguins don’t appear physically injured or malnourished, and the researchers found no traces of oil on their bodies, BBC reports. The lack of clues, paired with the sheer number of the penguins, have left scientists puzzled. The birds have been identified as Magellenic penguins, named for the Strait of Magellan, where they originated. They traditionally migrate each year from Argentina to Brazil during the Southern Hemisphere’s winter — or sometime between March and September.
The penguins were found beached between the towns of Tramandai and Cidreira, about 60 miles away from the state capital of Porto Alegre. Remains are still being investigated at Porto Alegre University, and the cause of death is expected to be released within a month.