Why are dolphins beaching themselves? 4 theories

Scientists aren't sure why the beloved marine mammals are getting stranded in unprecedented numbers this winter. But they have a few ideas

Buzzards fly around two dead dolphins on a beach in Peru: This year's unusual number of beached dolphins is being blamed on everything from warm weather to something they ate.
(Image credit: REUTERS/Janine Costa)

From New England to Peru, dolphins have been beaching themselves in unprecedented numbers in recent weeks. More than 177 short-beaked dolphins have been stranded on Massachusetts' Cape Cod — more than five times the normal annual number — and 124 have died. Researchers have screened the marine mammals for bacteria and viruses, analyzed tissue samples, and put tracking devices on some survivors released back into the sea, looking for a cause. "Gosh, it's a puzzle," biology professor Richard Connor tells The Boston Globe. "It's really strange." What's going on? Here, four theories:

1. Some coves and bays routinely trap dolphins

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2. It was something they ate

More than 200 dead dolphins have washed up on beaches in Chiclayo, Peru. But a potential clue — dead anchovies — has washed up beside them. Dolphins eat the tiny fish, leading the Peruvian Sea Institute to theorize that whatever killed the anchovies "could have poisoned the dolphins," says Liz Klimas at The Blaze.

3. Humans might be to blame

With no obvious culprit, scientists aren't ruling anything out, including explanations linked to humans. Man-made climate change, for instance, may have driven dolphins' prey into unfamiliar waters. The use of naval sonar could also be a factor. "We don't have that single answer," International Fund for Animal Welfare rescue and research manager Katie Moore tells the Cape Cod Times. "We want to look into every possible cause."

4. Maybe it's the weather

This year's unusually warm winter is affecting everything from animal reproductive cycles to hibernation patterns on land. "The change could also somehow be impacting dolphins," says Jennifer Viegas at Discovery News. "Unusual weather... is likely the main driving force, even if it is fueling some other secondary problems, such as the emergence of pathogens."