Sharks migrate for extreme distances, and scientists have wondered how they do this. Some assumed it may be down to their acute sense of smell, but it’s now thought the Earth’s magnetic field is key to their navigation
Scientists have questioned how sharks navigate
Some sharks are known to travel long distances, just like some birds and fish, with great white sharks impressively traveling from South Africa to Australia and back again. However, this raises the question of how. With some species having a superior sense of smell, this is one theory that has been introduced, but many believe that this would only help them along the end of their journey as they travel too far to rely on this alone.
The Earth’s magnetic field
Scientists now believe that the Earth’s magnetic field is the answer. Potentially using the same electromagnetic sensory organs that they use to track their prey, and with each part of the earth having a different magnetic signature, they believe the sharks utilize this as a way of knowing where they are. Perhaps having a kind of magnetic map in their brain, would explain how they travel such large distances without making a wrong turn?
The science behind the theory
A scientist wanted to test this theory, and Bryan Keller, a shark biologist, brought 20 juvenile bonnethead sharks to his laboratory at Florida State University. The species were chosen because they are known to return home to breed. He placed the sharks in a singular tank surrounded by a cube wrapped in copper wire. The scientist used this to imitate a location as the magnetic field will change depending on the amount of power running through it. Amending the magnetic field should show a change in the shark’s direction.
Did the experiment work?
A lot of the time, yes. When the sharks were exposed to the magnetic field around 375 miles south of where they were caught, most of them tried swimming north. However, when exposed to the magnetic field of where they had been caught, they swam in different directions. Bryan then exposed them to the magnetic field the same distance north, but the sharks didn’t appear to know where to go. Bryan noted this would make sense, as sharks don’t tend to go north of where they were caught due to there only being land there.
Is this the same for any other species?
Sea turtles are another species that can use the Earth’s magnetic field with a magnetic map. Even though they are born with the ability to read some of the magnetic maps, the rest is learned. Still, scientists aren’t yet sure if this is the case for sharks. A sensory neuroscientist at the University of Oldenburg in Germany, Henrik Mouritsen, agrees that it is too early to know for sure, but birds, which have been studied deeper, definitely show it as a learned behavior.
Using the Earth’s magnetic field to navigate is a huge milestone when it comes to understanding how sharks really know their way around the deep blue.