Rolling The Dice On When Sharks Eat

August 11, 2004

Release from: Kevin Butler
Press-Telegram.com

When is it safe to go back in the water? Many people say sharks are most likely to attack humans at dawn or dusk, says Christopher Lowe, director of the Shark Lab at Cal State Long Beach.

But is this an urban legend?

Lowe and his research partner decided to go to Las Vegas to find out. The pair visited the aquarium at the Mandalay Bay Resort and Casino to conduct research on the facility's nurse sharks in order to determine what times sharks feed.

There's a simple reason why many people associate shark attacks with dawn and dusk, Lowe says.

"The problem is the people who most get attacked are surfers, and when do surfers come out? Dawn and dusk," he says.

In fact, research suggests that sharks are not any more likely to feed at those times, he says.

Lowe and his partner Yannis Papastamatiou, a graduate student at the University of Hawaii, are using an innovative technique to study shark feeding times. Last week, the pair inserted probes into the stomachs of three nurse sharks to test how the stomachs' acidity and temperature change after the sharks were fed.

The approximately 4-inch-long titanium probes contain a computer and have a sensor on one end to test the acidity in the stomachs, which is different before and after eating. In about a week, the sharks will either regurgitate the probes or the researchers will extract them from the sharks' stomachs and read the information on the probe's computer.

Because this study was done in a controlled environment, the researchers will be able to correlate the changes in temperature and acidity to the times they knew the sharks were fed in the aquarium.

Shark scientists use those kinds of probes in sharks in the sea.

Scientists will be able to recognize when and how much sharks eat, by comparing their probes' data with that collected by Lowe and his partner at Mandalay Bay.

"The main reason for doing this is to say, OK, we are going to take this technology, and we are going to adapt it for use in wild sharks, so we can begin to answer some of these important questions and dispel some of these myths," Lowe says.

Lowe already has conducted similar tests on leopard sharks at the Long Beach Aquarium, he says.