How Sharks Find Their Way

Sharks can’t ask for directions. They don’t need to. Their toolkit puts ours to shame.

A shark navigates the ocean using several senses at once, and at least one of them is closer to a superhero power than to a human sense.

Smell comes first. A shark can follow a scent trail through the water over long distances, reading the faint chemical signals that spread out from another animal.

Hearing helps too. Sharks pick up low sounds — the thrum of a struggling fish, for example — from far away, because sound travels so efficiently underwater.

Feeling the water, and feeling electricity

Along a shark’s body runs a line of special sensors called the lateral line. It feels vibrations and tiny changes in water pressure, so a shark can sense a fish moving nearby without ever seeing it.

Then there are the ampullae of Lorenzini — jelly-filled pores, mostly on the snout, that detect tiny electric fields. Every living animal gives off faint electricity when its muscles move and its heart beats, and a shark can feel that. It can find a fish hidden under the sand by its heartbeat alone. Nothing humans have quite compares to it.

Sharks see well too, especially in low light. Many have a reflective layer behind the eye that bounces light back through the retina, helping them see in dim water — the same trick that makes a cat’s eyes shine at night.

The one that’s still a maybe

Here’s the part scientists are still working on. Some sharks might sense Earth’s magnetic field and use it like a compass to travel long distances. There’s suggestive evidence, but it isn’t proven the way the other senses are, so it’s best filed under “probably, maybe, we’re still checking.”

Did you know? The lateral line isn’t unique to sharks — most fish have one. But a shark’s is wired to some of the sharpest water-sensing in the sea.