Many animals have a sixth sense that we humans do not. It’s called magnetoreception, and it allows them to read Earth’s magnetic field to navigate.

The magnetic field comes out of the ground at the South Magnetic Pole, flows parallel to the surface across the equator, then dives back into the ground at the North Magnetic Pole.

Many bacteria, earthworms, and blind mole rats can sense the direction of this magnetic field and orient to it. We call this compass sense.

Migrating animals like butterflies, salmon, sea turtles, and many birds have a more advanced version called signpost sense. They read the direction and inclination of the magnetic field and create mental maps of local anomalies, or “signposts” within it, to chart their paths in three dimensions over great distances.

Scientists who study magnetoreception have found that some bacteria have particles of magnetite that align north–south. Some birds have proteins in their eyes sensitive to magnetic fields.

But for the more complex signpost sense, animals must have multiple magnetic receptors sending diverse signals that converge in the brain. And we still don’t know what those are or how they work.

One reason we may not understand magnetoreception is that we simply don’t know what it feels like, so we’re not quite sure how to study it.

We’ll look at other “sixth senses” of the animal kingdom in future episodes.