Plug a shark’s nose, and it’ll have a hard time getting home.
Some sea creatures can find their way through thousands of miles of seemingly featureless oceans. Even more impressive is the route that they take.
This is Scientific American’s 60-Second Science. I’m Jason Goldman. Got a minute?
[Andy Nosal:] Well, we’ve known for a long time that sharks are capable of long-distance migrations. How exactly do they know where they’re going?
Nosal and his team suspected that the navigational secret of some sharks might be their sense of smell. They use their keen noses to find food, of course. And other fish, like salmon, are known to use olfaction to navigate.
To see if his hunch was right, Nosal scooped up some adult female leopard sharks in their preferred environment—waist-deep water off the San Diego coast. He attached a small radio transmitter behind their dorsal fins. And he blocked the sense of smell in half of the sharks by shoving cotton balls soaked with petroleum jelly into their nostrils.
Nosal and his crew dropped the sharks about six miles away at a spot in the open ocean. The researchers then tracked the sharks as they tried to swim back home. Four hours later the sharks that could smell were two thirds of the way back home—and had swum in very straight paths. But the ones with stuffed noses took erratic routes and only made it about half as far.
Nosal thinks they all eventually got back home. Those jelly-soaked cotton balls eventually disintegrate, returning the sharks to normal. The experiment is the first to show that sharks can indeed sniff their way back home. [Andrew P. Nosal et al, Olfaction Contributes to Pelagic Navigation in a Coastal Shark, in PLoS ONE]
But it also shows that they must have some kind of backup system that lets them that lets them navigate nonnasally. For Nosal, the next questions are: What’s the backup system? And if sharks navigate by smell, what exactly is it they’re smelling that leads them—by the nose.
Thanks for the minute! For Scientific American, I’m Jason Goldman.
[The above text is a transcript of this video]
Executive Producer Eliene Augenbraun
Producer Lydia Chain
Narrator Jason Goldman
Podcast Producer Steve Mirsky
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Special Thanks: Andy Nosal and Kyle McBurnie