At the first hint of fall, Caribbean spiny lobsters form a long chain. As many as 50 lobsters may join together. They use their antennae to touch the backs of the lobsters ahead of them. It’s time for their annual journey, or migration.
Before winter, these lobsters leave shallow waters. They seek out deeper, warmer water. Here, the waves are less choppy. The ocean floor is still, and food is more plentiful.
To reach this place, they move single-file like a silent army. They creep along for as many as 50 kilometers (31 miles). But what drives them?
We know that many animals migrate. They move from place to place, often at certain times or seasons. Why? To search for food or for places to breed. But what triggers their urge to move?
The shorter days of fall and a sharp drop in water temperatures send the lobsters on their way. They use their knowledge of the underwater landscape to move. But they are also guided by Earth's magnetic field.
Some animal species can detect this magnetic field and use it to guide their migrations. Humans can’t sense the magnetic field. They must use a compass.
Some animal species have small particles of magnetite in their brains. This magnetic mineral may react with Earth’s magnetic field. Scientists think the mineral may activate nerves and send messages to the brain to help animals find their way.
Caribbean spiny lobsters link together when they migrate across the ocean floor.