| Leatherback biology | |
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Classification
Kingdom: Animalia General Scientists are not sure how long it takes leatherback turtles to mature or how long they live. Recent scientific work suggests that these turtles may grow rapidly and reproduce at a much earlier age than other sea turtles. Pink spot
Female leatherbacks nest an average of six times every two to three years. It is the only time adult leatherbacks return to land after hatching. Leatherbacks do not nest in Canada, but nest on tropical beaches. In the Atlantic, the major nesting beaches are in Suriname, French Guiana, Trinidad, Tobago, Costa Rica, and Gabon. Some leatherbacks even nest in Florida. The Atlantic leatherback's nesting season lasts from March to July. The turtles
nest at night, most of them return to the same beach each time they
nest, and most nest on the same beach on which they hatched. The
nesting process takes approximately two hours. The turtle hauls herself
out of the ocean onto the beach. Because leatherbacks have bodies that
are designed for the sea, they move very slowly on land using their
front flippers to drag themselves across the beach. Once she has picked a suitable spot, the female leatherback will dig a deep hole called an egg chamber with her rear flippers. After the chamber is complete, she will lay an average of 82 eggs. The eggs are about the size of a billiard ball and have soft shells. After the eggs are laid, the turtle will cover them with sand, completely filling in the egg chamber. Then, she will attempt to disguise the area where she nested by throwing sand in all directions with her front flippers. After the nest is properly concealed, she will lug herself back to the sea. She does not return to the nest again. Leatherback eggs incubate for approximately 65 days. Inside the nest, hatchlings use a sharp tooth called a "caruncle" or egg tooth to break out of their egg. The egg tooth will fall off soon after the turtles emerge from the nest. The baby turtles work sometimes for several days to dig out of their nest. The turtles erupt from the nest as a group, usually at night or during a rainstorm. The turtles travel immediately toward the sea. They find the sea by moving toward the brightest horizon, which is usually the reflected light from the water's surface. The trip from the nest to the ocean is the most dangerous of the leatherback's life. They are open to predation by birds or crabs. Baby sea turtles that find themselves on a beach near buildings with bright lights are also in danger of traveling toward those lights instead of the ocean. This increases their vulnerability to predation and puts them at risk of dehydration and subsequent death. The leatherback's growth rate after hatching, the age at which it reaches sexual maturity, and its life span are still poorly understood. Leatherbacks feed primarily on jellyfish. The major reason leatherbacks are in Atlantic Canadian waters in the summer is because of the abundance of jellyfish here. A single leatherback eats tens of kilograms of jellyfish a day. The leatherback's diet of jellyfish may help conserve fish species. Leatherbacks help keep the jellyfish population under control. This is significant not only because jellyfish compete with larval fish for food (both eat zooplankton), but because jellyfish are also known predators of larval fish. The leatherback has the largest geographic range of any reptile. It is found in the Atlantic, Pacific, and Indian Oceans. It is also one of the deepest-diving air-breathing vertebrates, and can dive as far as one kilometre. Several factors, including its dark body colour, a thick layer of fat, and a high volume to surface ratio, allow leatherbacks to maintain core body temperatures as much as 18 degrees Celsius above the surrounding water temperature. This means they can spend long periods of time in cold waters that would induce hypothermia in other sea turtles. Information from flipper tagging indicates that some Atlantic leatherbacks move from the tropical waters adjacent nesting beaches to northern latitudes, where the water is much cooler, and then back again. Unfortunately, because leatherbacks are difficult to study at sea,
scientists do not know enough about the species' habitat preferences.
Important questions, such as when and The red sections of this map indicate the range of the leatherback turtle in Canadian waters.
Map courtesy of M. Elliott, Environment Canada
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where the turtles are at risk in
the ocean, still need to be answered. The Leatherback Turtle Working
Group's