How do Sharks Sniff out a Meal? It is all in the timing!

A shark’s sharp teeth aren’t the only reason we find them so scary---their ability to smell blood in the water, even from a long distance, is also a big factor. We know they’ll find us.

But how do they know what direction to swim in order to find a wounded fish (or person)?

Conventional wisdom says that they follow trails of scent based on differences in the concentration of odour molecules detected by each nostril. Not so, say marine biologists in a new study in the journal Current Biology.

They say it’s all in the timing.

In an experiment based on the timing differences in smelling odours to which sharks were exposed, it was measured how quickly the shark turned and in which direction it swam were then recorded.

Perhaps not surprisingly, the sharks turned in the direction of the nostril that first received the odour, regardless of the concentration of that odour, when the timing difference was half a second or less. With a longer delay of a full second they received the odour in both nostrils at the simultaneously, the sharks didn’t know which way to turn and showed no preference for any direction.

Odours in air or water are not dispersed uniformly. These patterns can be quite chaotic and can be misleading if an animal were trying to determine the direction from them.

The timing differences to sniff out their prey may explain the evolution of the hammerhead shark’s distinctive shape. With their widely spaced nostrils--- at the far right and left of its flat head---may give hammerheads a better sense of smell.

Read the original Smithsonian article here: https://bit.ly/2D4ObE4