National Geographic : 1967 Jun
After incubating for about 60 days, baby turtles break out of their leathery eggshells and wriggle up through the sand, usually in the early morning hours. They burst out in flurries of little paddle-footed creatures, each the size of a silver dollar, and all with an inborn frenzy to scramble toward the sea (pages 881-2). Early Habits Remain a Mystery Every day we find them on the seaward side of their pens, put them in wooden tanks, and feed them chopped fish. When the turtles are about a year old and weigh from two to five pounds, their jaws are strong enough to crop turtle grass. From then on, they are mainly herbivorous. We still don't know what young turtles eat or where they go during their first year in the sea. The thousands of Tortuguero hatchlings we airlift to other areas may rejuvenate extinct rookeries. We hope that the young turtles, imprinted by the smell, taste, or feel of such release sites as Bimini, or Cape Sable in Everglades National Park, will instinctively return there to breed when they mature. On a recent Operation Green Turtle stop at Barbados, a ring of spectators watched as we opened six crates and freed 1,200 little turtles on the beach. All scurried across the snow-white sand toward the surf. "They headin' fo' Tettel Bogue," a young Barbadian yelled. It is a worrisome thought that the boy could have been right. To date there is no clear evidence of renewed nesting at for mer breeding grounds we have stocked. Two important uncer 886 tainties trouble the restoration program. One is that nobody Fitted with goggles that filter sky color, a female kicks up sand (top, left) as Dr. David Ehrenfeld of the University of Florida struggles to right her for a sea-finding experiment at Turtle Bogue. Spread-eagled like a sun-worshiper (above), she wears goggles whose interchangeable lenses depolarize the light or, alternately, let through red, infrared, green, blue, or ultraviolet rays. Blundering off, she eventually finds the water but her zigzag track reveals confusion (right). Sight rather than sound, smell, or vibration guides females and hatchlings to the sea. This experiment tests a theory that sky coloration steers them. But results from turtles goggled day and night proved to Dr. Ehrenfeld that the brightness of the sea's horizon, not sky color, leads turtles to the water.