Hippos are suffocating thousands of fish with their lethal poop

Researchers have finally figured out what is responsible for the thousands of dead fish washing up on the banks of the Mara River between Kenya and Tanzania: It was Mr. Hippo in the pool with … well, with a whole lot of poop.

Hippopotami, the researchers discovered, create so much waste that it actually suffocates hundreds and hundreds of fish to death when their sewage flushes downstream, The Atlantic reports. Every day, some 4,000 or so hippos crowd into "hippo pools" near the Mara River, where they keep cool and safe from the sun. But as a result, "there's hippo feces everywhere. Over the rocks. Over the bottom," said Chris Dutton, one of the researchers.

Just how much? Try 18,740 pounds in about a 62-mile stretch of water.

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All that dung is consumed by bacteria, which also pulls the oxygen out of the water. Combine the lack of oxygen with the "ammonia, methane, hydrogen sulfide, and other chemical grotesqueries" that occur in the bottom of what is essentially a gigantic communal hippo toilet, and you have yourself the perfect murder weapon, The Atlantic writes. When rains come, the lethal water pours downstream, and the low oxygen levels smother innocent fish along the way.

Learn more about the toxic waste, and how the researchers got to the bottom of the mystery, at The Atlantic.