Large-Shark Hunting Habits Exposed by Crittercam

Stefan Lovgren
for National Geographic News
January 23, 2004

This story is one of a series looking at National Geographic Crittercam research. Crittercam is a research instrument worn by wild animals and equipped with a video camera and other information-gathering equipment. Crittercam is used on animals both in the ocean and on land.

To learn more about the Crittercam's field test, tune in to the Crittercam: Large Sharks episode on the National Geographic Channel in the United States on Saturday at 8 p.m. ET. Got a high-speed connection? Click here to watch previews of the Crittercam television documentaries on the National Geographic Channel Web site.

Mike Heithaus is used to the public image of sharks as mindless killing machines. But one thing he's learned from using crittercam is that "sharks are a lot more boring than you'd expect."

"Tiger sharks may be capable of taking out big prey," said Heithaus, who is known as one of the world's leading shark scientists. "But they'll turn toward a turtle and if the turtle just looks at him, the shark will not even try to attack. He'll wait to make the sneak attack where he's not going to have to put a lot of effort into killing the prey."

Now a marine biology professor at Florida International University in Miami, Heithaus was a research fellow with National Geographic Society's Remote Imaging Program and the host of the Crittercam series. He's been fitting crittercams on sharks since 1997, first on tiger sharks in Australia and more recently on bull sharks and hammerheads in Florida.

His mission: to learn more about the sharks' foraging behavior and where they spend their time. The research has already shown that sharks have the power to change their underwater environment.

"Because sharks are top predators, they can influence the population sizes of their prey," Heithaus said. "They keep their prey in check, and that in turn helps their prey's prey. These effects can cascade through the whole ecosystem."

Lazy Predators

Heithaus was studying dolphins before turning to shark research in 1997. He says he stumbled into it by accident.

"I was interested in where dolphins spend their time," Heithaus said. "It turned out that during some seasons dolphins were nowhere near where we expected them to be, based on their food. I thought, maybe it has something to do with their predators. So we started to look at tiger sharks."

He was surprised to learn that virtually nothing was known about tiger sharks, even though they're big animals. The average tiger shark is about ten feet (three meters), but some can grow over 15 feet (4.6 meters) long. Heithaus says he was immediately hooked.

"They're perfectly adapted predators, really efficient hunters," he said. "And they've been around for hundreds of millions of years."

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