Sharks smell their way to shore

  • A group of Leopard sharks were captured and tagged to decipher how they navigate vast distances in such straight lines.
  • Some had their sense of smell impaired before release, and were largely unable to find their way to shore.
  • The results have implications for how other migratory animals and birds carry out similar long distance journeys.

Sharks have an extraordinary ability to navigate in almost dead straight lines over vast distances in the ocean. But exactly how they do this is still somewhat of a puzzle.

Now, research suggests that their nose is a vital tool that detects small chemical changes in the water, and allows the shark to navigate straight to their destination of choice.

“This study is the first to demonstrate experimentally that olfaction [sense of smell] participates in open-ocean navigation by sharks.” write the scientists behind the new study, which is published in the open-access journal PLOS ONE.

It is possible that other migratory sea animals use this navigational technique to travel long distances in relatively straight paths.

A bunged up nose sends shark off-course

During the experiment, 25 leopard sharks were briefly captured near the shore, and tagged. Half had their sense of smell temporarily impaired with cotton wool soaked in petroleum jelly. The other sharks’ sense of smell was not changed.

They were transported 9 km offshore, where they were released. The scientists tracked them for around 4 hours using the acoustic tags attached earlier, to see where they went.

Sharks with no sense of smell did manage to get closer to the shore, but only by about 37 per cent on where they started. And they took interesting routes that could only be described as “random” by the scientists behind the research.

But amazingly, the sharks that could smell found their way back to shore with no problems, said lead-author Andrew Nosal, a post doc researcher with Scripps Institution of Oceanography, USA, to Discovery News.

These sharks ended up 63 per cent closer to the shore compared to where they started, and did so in almost straight lines.

Other sensory cues to be investigated

According to Nosal, the results show one way in which sharks use their nostrils to navigate, by detecting small chemical changes–probably due to plankton or amino acids–in the water.

“Although chemical cues apparently guide sharks through the ocean, other sensory cues likely also play a role,” says Nosal in a press release.

“Future work must determine which environmental cues are most important for navigation and how they are detected and integrated,” he says. [wp-svg-icons icon=”mug” wrap=”i”]

 

Watch Andrew Nosal describe his research into Leopard sharks.

 

Time for a bit more? Read on…

Looking for more reading on this topic? First off, why not try reading the original open-access scientific article.

If that is a step too far, then try the original press release.

Check out the lead-scientist Andrew Nosal’s research profile on LinkedIn.

 

 

Research Blogging:

ResearchBlogging.org

Nosal, A., Chao, Y., Farrara, J., Chai, F., & Hastings, P. (2016). Olfaction Contributes to Pelagic Navigation in a Coastal Shark PLOS ONE, 11 (1) DOI: 10.1371/journal.pone.0143758

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