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Sharks use Earth’s magnetic field as ‘nature’s GPS’

Patrick Whittle, May 23, 2021 3:00PM AP

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Bonnethead sharks like this one have been found to use the Earth’s magnetic field to help them navigate the ocean. Picture: Joe Klamar/AFP media_cameraBonnethead sharks like this one have been found to use the Earth’s magnetic field to help them navigate the ocean. Picture: Joe Klamar/AFP

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Sharks use the Earth’s magnetic field as a sort of natural GPS* to navigate journeys that take them great distances across the world’s oceans, scientists have found.

Researchers said their marine laboratory experiments with a small species of shark confirm a long-held theory that sharks use magnetic fields to help them navigate* — like some other marine animals such as sea turtles.

Their study, published in the journal Current Biology, also helps explain why sharks are able to traverse* seas and find their way back to feed, breed and give birth.

“We know that sharks can respond to magnetic fields,” said marine policy specialist Dr Bryan Keller, one of the study authors.

“We didn’t know that they detected it to use as an aid in navigation … You have sharks that can travel 20,000km and end up in the same spot.”

media_cameraDr Bryan Keller holds a bonnethead shark. Picture: Colby Griffiths/AP

The question of how sharks perform long-distance migrations* has intrigued* researchers for years. The sharks make their journeys in the open ocean where there are few physical features such as corals that could serve as landmarks to help them identify where they are.

Looking for answers, scientists based at Florida State University in the US decided to study bonnethead sharks — a kind of hammerhead that lives on both American coasts and returns to the same estuaries* every year.

Researchers exposed 20 bonnetheads to magnetic conditions the same as those from locations hundreds of kilometres south from where the sharks were caught off Florida.

The scientists found that the sharks began to swim north when the magnetic signals made them think they were south of where they should be.

“It had been unresolved* how sharks managed to successfully navigate during migration to targeted locations,” Dr Keller said.

“This research supports the theory that they use the Earth’s magnetic field to help them find their way; it’s nature’s GPS.”

Senior scientist emeritus at Mote Marine Laboratory and Aquarium Robert Hueter, who was not involved in the study, said the finding was compelling*.

Dr Hueter said further study was needed to find how the sharks used the magnetic fields to determine their location and whether larger, long-distance migrating sharks used a similar system to find their way.

“The question has always been: even if sharks are sensitive to magnetic orientation*, do they use this sense to navigate in the oceans, and how? These authors have made some progress at chipping away at this question,” he said.

White Shark media_cameraDr Bryan Keller believes other sharks, like great whites, also probably use the Earth’s magnetic field to help them navigate.

Dr Keller said the study could help to manage the world’s shark species, which are in decline. An earlier study this year found that the number of sharks and rays in the world’s oceans dropped more than 70 per cent between 1970 and 2018.

Dr Keller said the bonnethead’s use of the Earth’s magnetic field was probably shared by other species of sharks, such as great whites, that travel long distances across oceans.

GLOSSARY

  • GPS: Global Positioning System tells you where you are on Earth using satellites in space
  • navigate: find the way
  • traverse: travel across
  • migrations: the movement of animals at different seasons
  • intrigued: been of interest, caused curiosity
  • estuaries: places where a river meets the sea
  • unresolved: not decided, not agreed
  • emeritus: retired but still allowed to hold the title
  • compelling: very exciting and interesting, makes you want to know more
  • orientation: being guided in a direction

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QUICK QUIZ

  1. The study found that sharks use what to help them navigate?
  2. What type of shark did the researchers study?
  3. Where do these sharks live?
  4. How many sharks were used in the study?
  5. Shark numbers declined by what percentage from 1970 to 2018?

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CLASSROOM ACTIVITIES
1. Animal study
As mentioned in the news story, there are many animals that are known to use the Earth’s magnetic field to help them navigate. Choose another animal who does this, research what is known about how they navigate and write a short summary to explain.

Time: allow 25 minutes to complete this activity
Curriculum Links: English; Science

2. Extension
Find out more about Earth’s magnetic field. Write down the five most interesting facts you discover.

Time: allow 20 minutes to complete this activity 
Curriculum Links: English; Science

VCOP ACTIVITY
Grammar and VCOP
The glossary of terms helps you to understand and learn the ambitious vocabulary being used in the article.

Can you use the words outlined in the glossary to create new sentences? Challenge yourself to include other VCOP (vocabulary, connectives, openers and punctuation) elements in your sentence/s.

Have another look through the article, can you find any other Wow Words not outlined in the glossary?

Extra Reading in animals