Reaching 40 feet long and weighing up to 15 tons, whale sharks are the world’s largest fish. They feed by filtering plankton and fish eggs from a vortex created by their opening mouths — and as shown in a first-of-its-kind photograph of a whale shark pooping, activities at the other end of the fish are equally behemoth in proportion.

Georgia Aquarium zoologist Alistair Dove snapped the photograph from the window of a Cessna plane during a recent research trip to the Gulf of Mexico, where he studies whale sharks. He’s been less successful in capturing whale shark defecation in the water, though not for lack of trying. It’s hard to keep up with the fast-cruising giants, and their deposits fall quickly. And for a zoologist like Dove, the feces are research treasure.

“Nobody has done this analysis yet,” said Dove, who referenced a scene from Jurassic Park, when Laura Dern’s character is ecstatic at the chance to poke through a pile of dinosaur droppings. “It could be a literal gold mine.”

With a fresh sample, researchers could perform high-powered chemical and genetic analyses of its contents, learning in precise detail what these threatened giants consume in the wild. Dove is especially curious about their digestion. In aquariums they thrive on a relatively spartan diet, suggesting high efficiency in converting food. But a colleague on the research trip had observed whale shark defecation first-hand, and said their food was barely digested.

“He says it comes out looking much the same as when it goes in,” said Dove. “Maybe they’re efficient when food is scarce, but when they find a good patch, their efficiency drops in favor of gluttony. They’re eating so much, they just push it through.”

That colleague happened to find a group of whale sharks feeding — a spectacular affair, in which scores swim in a synchronized frenzy, sucking up water and food, and discharging wastes on the spot.

“Pooping events may play important oceanographic roles,” concentrating surface nutrients and delivering them to the water column and seafloor, said Dove. Scientists now think that baleen whales perform just such a task, and may be vital to nutrient circulation in the ocean.

Dove estimated the main plume in the photograph to be 30 feet long and 20 feet wide, and the smaller about 8 feet by 10 feet. If it’s three feet thick, the nutrient slurry would have a volume of 2,000 cubic feet. “Imagine you’ve got a big aggregation, dozens or hundreds of whale sharks, doing this all at the same time. That’s a lot of nutrients,” he said. Dove hopes to collect samples from just such a group.

“You can never go wrong with toilet humor, but there’s some substance to it. So to speak,” said Dove.

Images: 1) Alistair Dove/Georgia Aquarium. 2) Flickr/Cotaro.

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