The world’s biggest fish are hungry migrators on a mission, according to a tracking study that mapped whale sharks’ long journeys around the Gulf of Mexico and Caribbean to a favorite feeding hot spot off the Yucatan Peninsula.

And one whale shark’s incredible 5,000-mile (7,200-kilometer) swim could even help solve the long-standing mystery of where whale sharks give birth—an event no scientist has ever seen.

The largest-ever study of whale shark migrations, nine years in the making, shows that the hundreds of school bus-sized animals that feed in a plankton-saturated stretch off the Mexican coast come from far and wide.

The gentle giants—which can reach up to 40 feet (12 meters) or longer in length, and weigh an average of 5 tons—use mouth filters to feed on the tiny plankton and small fish or eggs.

Read more in National Geographic