Why It Doesn't Pay to be On a Shark's "Wrong" Side

By: Charles Cooper
Topics: Tech Talk

If a fish gets caught swimming near a shark, it obviously risks winding up as an entree. That much is obvious but sharks encounter lots of fish during the course of a day. So how do they decide which prey to pursue?

It comes down to timing.

"What's for dinner?"

(Credit: Wikimedia)

In a study appearing in the current issue of the journal Current Biology, researchers have concluded that when presented with different scents, sharks will turn in the direction of the first odor they pick up if there is a small delay between them.

Eight dogfish sharks were captured near Cape Cod and transferred to a lab at the University of South Florida, where they were outfitted with headstages and tubing that was set just inside the inflow nostrils. Tubing pumped in squid rinse as the odor source.

The testing was synchronized via the use of a personal computer. In their testing, the researchers presented the test sharks with a variety of odor pulses. They found that the sharks would turn toward the first side which got stimulated, even if the other side emitted a more concentrated smell. By contrast, when there was no delay or if presented with one that extended too long, the sharks' choice of direction basically turned into a coin flip.

This finding about time lags contradicts the widely-held belief that sharks respond primarily to the stimulus of odor concentrations in the water. Shark researchers had believed that after the animals picked up scents through their nasal cavities, they would head in the direction of the strongest smell (assuming there were differences between the scents.)

"This is the first conclusive evidence that under semi-natural conditions and without training, bilateral time differences trump odor concentration differences," write co-authors Jayne Gardiner and Jelle Atema.

Charles Cooper is an executive editor at CNET News. He has covered technology and business for more than 25 years, working at CBSNews.com, the Associated Press, Computer & Software News, Computer Shopper, PC Week, and ZDNet. E-mail Charlie.