To be the efficient predators and scavengers that they are, sharks have an amazing array of sensory functions - from smell, sight, hearing/vibrations, to sensing electrical impulses. Working in coordination or in a sequence, these capabilities give sharks the edge to survive whether cruising an ocean reef or plying the wide open oceans hundreds of miles offshore.
Now, new research by the Woods Hole Oceanographic Institution (WHOI) and the University of South Florida shows how shark's sense of smell is even more refined than previously thought, by sniffing scents one nostril at a time - a sort of stereo smell-o-vision!
In a recent press release, WHOI researcher Jelle Atema said, “The structure of an odor plume is chaotic and not at all coherent. It’s just like what you see with the Gulf oil spill, which is essentially a gigantic odor plume. The plume breaks up into pieces, floats to different levels and gets transported in a current.”
By determining which nostril detects the odor first, the shark is able to determine a direction, much like our stereo hearing allows us to determine direction based on which ear detects a sound first or with greater intensity. The researchers confirmed this with tests using smooth dogfish, a small shark local to New England waters, and squid odor as an attractant.
But as Atema said, odors are transported rather haphazardly by currents, so sharks bring another sensory ability into play to help steer them in the right direction: the lateral line. This sensitive organ along a shark's body can detect faint vibrations in the water - vibrations like those given off by an injured fish or by the movement of water currents. Previous studies by Atema and fellow colleague Jayne Gardiner of the University of South Florida, showed that sharks use the lateral line to detect the direction of subtle currents - much like sensing wind on the hair of our bodies but with much, much greater sensitivity.
Combining these sensory abilities - stereo olfactory perception and lateral line vibrations - sharks are able to determine a direction and follow an odor to its source. “Inspired by odor, sharks also look for current,” Atema said. “The two together is what makes them so efficient.”
One more reason to look at sharks with awe and fascination and not ignorance or fear.
Read the Woods Hole press release.