Sea turtles have swum in Earth’s oceans for more than 100 million years as air-breathing reptiles adapted to life at sea, ranging from the small Kemp’s Ridley turtle at 100 pounds to the leatherback turtle at up to 2,000 pounds. Sanibel’s beaches provide nesting ground primarily for loggerhead and green turtles, and four of the seven sea turtle species have nested on Sanibel. One of the first and longest-running sea turtle research and monitoring programs began here at the lighthouse in 1959 under Charles LeBuff, and today more than 100 SCCF volunteers monitor the beach daily from May to October, looking for the distinctive tracks left by female sea turtles coming ashore. Nests are marked for protection and monitoring, and three days after a nest hatches it is dug to inventory the nest. All sea turtle species are protected by the U.S. Endangered Species Act. Sea turtles spend their whole lives in the ocean except when females come ashore to nest, and hatchlings emerge at night with the instinct to go to the brightest horizon, which on natural beaches is the water. Sanibel has between 125 and 350 nests every year. Human threats to sea turtles include pollution, marine debris, beachfront lighting, destruction of nesting habitat, commercial fisheries, and sport fisheries.