While you may remember the five senses from elementary school, those are only just what us humans are capable of. Animals of all different shapes and sizes sense the world in different ways. Take the spiny lobster for example. It has eyes for rudimentary vision. Its antennae and the tiny hairs lining its body allow the lobster to feel its surroundings. Chemosensors on the mouth, antennae and legs of the lobster give the animal a sense of smell and taste. In fact, lobsters “talk” to each other using chemicals that are emitted in their urine (yes, lobsters pee on each other to communicate). But one of the most remarkable senses is that of magnetorecption.
Magnetoreception is a magnetic sense, or in other words, a compass sense that acts like the magnetic compasses humans use to navigate.
Here’s a figure from a research paper* showing how lobsters orient towards their home range (the capture site) when presented with the magnetic fields of the indicated locations:
The lobsters tend to head to their homes and the scientists showed that the lobsters were using the Earth’s magnetic field to do this.
Many animals demonstrate such a magnetic compass sense including sea turtles, birds and fish. However, scientists are still trying to figure out how animals detect the Earth’s magnetic field. Pigeons have been an animal of particular focus in the quest to find this magnetic organ. Magnetite, an extremely magnetic mineral, has been found in the upper beak of the pigeon and could serve as the basis for a compass. There is also evidence that some cells in the pigeon eye are affected by magnetic fields. Other potential magnetoreception mechanisms have been suggested for pigeons but it’s unclear how these different proposed magnetic organs interact. Recent work in rainbow trout has pointed to a specific region of the brain, the trigeminal system, as the locus for magnetoreception processing but much work remains before we can understand the mechanism underlying the magnetic sense.
*Boles, L. C., & Lohmann, K. J. (2003). True navigation and magnetic maps in spiny lobsters. Nature, 421(6918), 60–63.