Animals with internal compass: how they use the magnetic field to not get lost

In nature there are animals that, without maps or GPS, are able to return to the exact place where they were born. Among them are sea turtles, migratory birds, fish and some amphibians. All these species share a superpower: they perceive the Earth's magnetic field.

Scientists speak of "magnetoreception" to describe this sense. In the case of some amphibians and fish, it has been observed that they can orient themselves even when moved tens of kilometers from their place of origin, which suggests they use magnetism as a mixture of compass and map.

There are several hypotheses about how this ability works. One of the best known proposes the presence of tiny magnetite crystals in certain body cells, capable of aligning with the magnetic field. Another line of research points to chemical reactions very sensitive to magnetic fields in certain proteins in the eyes.

Although there is still no single explanation, the combination of laboratory experiments, GPS tracking and physical models is revealing that this sense is more common than previously thought. Fish, reptiles, amphibians, birds and even some mammals could be using magnetic information in different ways according to their ecology.

Understanding how these animals orient themselves is not just a curiosity. It also helps to assess the impact that human infrastructure, pollution or changes in the local magnetic field can have on them, and to design better conservation strategies for migratory species that depend on extremely precise navigation.