Young mackerel escort a Pacific loggerhead turtle off Baja California.
Many of these 300-pound sea turtles are born on Yaku Shima in southern Japan, says Wallace J. Nichols, a California Academy of Sciences biologist.
Over the next two to six years the turtles cross the Pacific along a line, says Jeffrey Plovina of the National Marine Fisheries Service, that runs between cool water rich in plankton (green in the satellite image below) and warmer water low in plankton. As the cool water sinks be- neath the warm, it traps buoyant creatures like jellyfish, a favorite food of turtles.
Once the turtles reach Baja, they gorge on pelagic red crabs. Some loggerheads make the return journey. A few months ago, Nichols tracked a female as she swam back toward Japan.