SANTA ROSA NATIONAL PARK, COSTA RICA—It's just after 10:30 p.m. and the Milky Way decorates a moonless sky over Costa Rica’s Playa Nancite, a remote, half-mile-long beach. Surf-size waves crash on the coast as our National Geographic team waits for one of the world’s most mysterious migrations: a flotilla of olive ridley sea turtles coming ashore to build their nests.
Our headlamps glow red so that we don’t distract the animals, but every once in a while we flash white rays over the sand to get a better look at the scene in front of us.Like zombies, thousands of the two-foot-long turtles march up to the beach over the next few hours. They’re making their way ashore to nest,