Massive Dolphin Die-Off in Peru May Remain a Mystery

Thousands of dead or dying dolphins have washed ashore in Peru since January, a marine mystery potentially caused by a combination of stress, pollution and disease.

LIMA, Peru -- When a retired fisherman called to report that about 1,500 dolphins had washed up dead on Peru’s northern coast, veterinarian Carlos Yaipén’s first reaction was, “That’s impossible.”

But when Yaipén traveled up the coast last week, he counted 615 dead dolphins along a 135-kilometer stretch of coastline.

Now, the death toll could be as high as 2,800, based on volunteers’ counts. Peru's massive dolphin die-off is among the largest ever reported worldwide.

The strandings, which began in January, are a marine mystery that may never be unraveled. Experts say the causes could be acoustic impact from testing for oil or perhaps an unknown virus or other pathogen. Little marine research takes place in Peru, and even in the United States, of 55 marine mammal strandings since 1991, the National Oceanographic and Atmospheric Administration (NOAA) has classified 29 as “undetermined.”