Leatherback Seaturtle: Dermochelyidae

Like other turtles, the leatherback seaturtle is cold-blooded, meaning that its body temperature gets cooler when the outside temperature drops and warmer when the outside temperature rises. In most turtles, body temperature very closely matches the outdoor temperature. The seaturtles are a little different. Because they are so large and their muscles heat up when they swim, they can stay warm much longer than a smaller turtle can. They also have oily skin that acts like a jacket, to help keep the body warm. For these reasons, they are able to travel to much colder waters, like those off Alaska or Iceland. These turtles take advantage of this ability to travel to warm and cold waters. They often swim very long distances in what are called migrations (my-GRAY-shuns), moving from one region or climate to another to find food and to lay their eggs. Scientists have tracked some turtles that have swum as far as 3,100 miles (4,989 kilometers) one way to go from a nesting site to a feeding site. On average, these turtles swim about 19 miles (30.5 kilometers) a day for weeks at a time.

Many leatherback seaturtles may join together at a particularly good feeding site, like a school, or group, of jellyfish. They also hunt for food alone. Seaturtles are excellent divers, and they can swim down to more than 3,300 feet (1,006 meters) to find deep-water animals to eat. Turtles do most of their diving at night, but they are active both day and night.

Scientists know very little about courtship or mating in leatherback turtles. The turtles may mate before or during the long migration from a feeding area to a nesting area or just offshore from the nesting site. Females make their nests about once every three or four years on tropical beaches. Those that live in the Atlantic Ocean nest from April to November. Pacific Ocean leatherbacks nest at different times of the year, depending on the beach they choose. A small group of females usually nests together on one beach.

The females climb up onto shore, usually at night, and find a spot on dry land. They typically pick a nesting site that is just beyond the highest point that water reaches. Like the upper shell, the lower shell of leatherbacks is softer than that of most turtles, so the females choose sandy rather than rocky beaches to crawl over and dig their nests. They use both their front and back legs to dig a wide hole that can fit the entire body. Then they continue to dig a smaller, deeper pit with just the rear legs. Each female lays 47 to 263 eggs in the pit. Only some of the eggs hatch. From the time she lays them, 1 to 103 eggs have no yolks and so cannot develop into turtles. The rest are normal eggs. Eggs are round and range in diameter, or width, from 1.9 to 2.6 inches (4.8 to 6.6 centimeters) in diameter. Each egg weighs 2.5 to 3.2 ounces (71 to 91 grams).

Usually, the biggest females lay the most eggs and the largest eggs. In addition, turtles of the Atlantic typically lay more eggs than those of the Pacific, and nests made during the middle of the nesting season often contain more eggs than nests made earlier or later. Females may make up to eleven nests a year, although five or six is more common. Once she lays the eggs, the female uses her hind legs to cover them with sand and then continues with her front and rear legs to bury the larger body hole. She then leaves the area and provides no care for the eggs or the newly hatched young.

The eggs hatch in sixty to sixty-eight days, although some may hatch in as little as fifty days or as much as seventy-eight A newly hatched leatherback sea turtle makes its way into the ocean. (AP/Wide World Photos. Reproduced by permission.) days. If the beach, and therefore the nest, is especially warm about halfway through the eggs' development, most of the eggs hatch into females. If the nest is particularly cool, most of the eggs will hatch into males. The hatchlings wait until nightfall to climb out of the nest and onto the surface of the beach. They then head to the area that is most open to the sky and is the most brightly lit—usually the ocean. The young turtles continue to grow at sea, and when the reach the age of thirteen to fourteen years, they are ready to become parents themselves.