When immersed in shark-infested waters, staying inside a cage does not mean staying out of a shark's reach, as marine scientists recently found out firsthand.
A great white shark was caught on video defecating in front of a captive audience of scuba divers.
To the many smaller fish in the water, the massive yellow plume was far from gross. It might as well have been a dinner bell. The video shows them swarming toward the mass. [Image Gallery: Great White Sharks]
"Snack time!" Alistair Dove, senior scientist at the Georgia Aquarium in Atlanta, told LiveScience. "Unsavory indeed, but chunks of predigested food from a top-level predator's poop still contain enough useful carbon for smaller animals to make a meal of it."
Scientists get equally giddy over an elusive sample of fresh shark poop. They analyze the waste for clues about what the fish eat, among other things.
"When it's as hard to get your hands on an animal to take samples as it can be with many shark species, you're left with the samples they give you," Dove said. "Feces can tell you about what they are eating, but also a lot of other things."
The excrement also contains residual DNA from intestinal cells, so scientists can get gene sequence information and maybe even work out where the shark came from, Dove said. Some scientists also have developed tests that use the poop to study the shark's stress and sex hormones.
"The ability to test these without having to touch and therefore stress an animal yourself opens up several research possibilities," Dove said.
The plume appears yellow In the video, but Dove suspects the seawater is distorting the color. Shark poop is actually closer to green, Dove said.
These shades in poop come from a combination of the breakdown of blood and muscle pigments in the sharks' food, the green-colored bile that does the breaking down, and the yellow pigment bilirubin, which comes from the breakdown of the shark's own red blood cells, Dove said.
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Brett Israel is a staff writer for OurAmazingPlanet. Email Brett at email@example.com. Follow him on Twitter @btisrael.