One of the ocean's most unusual sharks, the thresher shark, has carried with it a great mystery: why the elongated upper caudal (or tail) fin? Suspicions were that it was used to strike and stun its prey. However, there wasn't any definitive documentation (ie: video or motion picture footage) to confirm it. Until now. . .
According to the BBC News, Dr. Chugey Sepulveda of the Pfleger Institute of Environmental Research in Oceanside, California, captured some brief images of a thresher shark swatting several smaller fish and stunning or outright injuring them, making them easy prey.
The water visibility is a bit murky and it all happens in a blink of an eye, but the video slows it down to half speed and you can clearly see the shark's unique hunting ability. The BBC doesn't allow for embedding a video, so click on the image below to link to the BBC and view the footage.
Followers of great white sharks at Isla Guadalupe are very familiar with the Pfleger Institute as they were one of the first organizations to do an exhaustive picture cataloging of the island's population of white sharks that migrate there every fall.
Kudos to the Dr. Sepulveda. These are very special sharks - all three species of thresher sharks are listed as "vulnerable to extinction" by the International Union for Conservation of Nature (IUCN).