Physics in the animal world: how sharks navigate using the earth’s magnetic field

Biologists have long believed that sharks sense the earth’s magnetic field and navigate through it. Now, finally, there was a scientist who proved it.

Every year, great white sharks make a long journey of 20,000 km, covering the distance from South Africa to Australia. On the way, they do not turn anywhere, the travel trajectory is an almost perfect straight line. And that’s not all – they not only swim to Australia, but also come back. Naturally, there are no more or less recognizable signs in the water that help these fish to navigate. Moreover, along the way, there are different currents, the water temperature changes, the day changes to night. But sharks swim in a straight line without losing their way.

For decades, scientists have debated the theory that sharks sense the earth’s magnetic field, using it to navigate space. But a shark is not a dove, it is quite difficult to practically confirm the theory. White sharks grow to enormous sizes – up to 6 meters in length and weighing up to a ton or even more. It’s hard to imagine a laboratory in which you can create a reservoir with these huge fish and test something there. But this problem was nevertheless solved, the results of the study published in Current Biology.

To prove the hypothesis, Brian Keller, a researcher at Florida State University (FSU), created a system capable of creating magnetic fields of different configurations. He built a 3-meter cube of wood with a large tank in the center. He also wound about 2 km of copper wire on a cube. When connected to a power source, this winding generates a magnetic field. By adjusting the flow of current, Keller will be able to generate a magnetic field of different configurations, simulating certain conditions that sharks may encounter in the ocean. Using his system, Keller decided to test whether a shark placed in a water tank would react to changes in the magnetic field.

This method has already been used to study the capabilities of other marine animals, such as turtles. Keller, convinced that sharks can sense magnetic fields (as shown by other scientists), decided to find out exactly how these huge fish use their skills. “For the study, we needed a species of shark that migrates, but small in size. I opted for the small-headed hammerfish, ”said Keller. This species of shark huddles in schools that migrate from the coast of Florida to the Gulf of Mexico, where they spend the winter.

Keller tested sharks with simulations of three different magnetic field configurations. One configuration corresponded to the Florida coast. The second is a point 600 km south of the usual hammerhead route, and the third is a point 600 km from the region in Tennessee, where these sharks have never been and could not be. The first two configurations did not have much effect on the fish. But the third – yes, during the test, the fish began to swim so that their head was pointing north. Keller came to the conclusion that sharks are not only able to sense the magnetic field, but also move due to this skill in a certain direction.

Keller’s research interested other scientists related to the topic of orienting animals through the magnetic field. For example, Kenneth Lohmann, professor of biology at the University of North Carolina, considered Keller’s study a clear demonstration of the capabilities of sharks. Lohmann had previously discovered and studied similar abilities in salmon and sea turtles. Probably, he believes, the ability to orientate with the help of a magnetic field is widespread in migratory marine animals.

According to Lohmann, young sharks remember the magnetic “address” of their home region, which helps them migrate thousands of kilometers, always returning to their native places.

As for other animals, the same salmon, in addition to the magnetic field, also use the sense of smell to determine their “native” places. Perhaps, sharks act in a similar way, in which the sense of smell is extremely well developed.

Another important question is how exactly sharks or other living organisms sense the magnetic field. This is a real mystery. There is an assumption that small crystals of magnetic matter are “built in” into any organ. Perhaps crystals of this substance are located somewhere in the nervous system. The second assumption is that magnetic fields affect the receptors of the visual system of a fish, turtle or other living organism. As a result, when orienting to the north, the surrounding “picture” turns red. If so, then it turns out that animals have something like a primitive augmented reality headset.

Sharks also have special senses called ampoules of Lorenzini… They are responsible for electroreception and have reached their maximum development in cartilaginous fish (sharks, rays and chimeras). These organs allow fish to pick up electrical fields and notice extremely small changes in their strength.

According to scientists familiar with Keller’s study, it is important because it provides an opportunity to understand the mechanism of fish migration. Probably, such studies will help to understand whether the mechanism of migration is hindered by underwater communications laid by humans – for example, underwater cables running along the bottom from wind generators located in the sea to the coast. Perhaps the electric current, which generates a weak magnetic field, will knock schools of fish and other marine animals out of the way.

So far, nothing is clear with this question. It is possible that technological structures somehow affect animals, perhaps they affect some species, others do not. There is also the likelihood of a complete absence of any influence of human energy installations on animals. But in any case, you need to be careful not to harm the animals that migrate using the magnetic field.

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