Sea creature called leatherback turtle. Janet O'Regan of Florida Atlantic University has shown that there are advantages of the leatherback streamlined shape. Swimming leatherback turtles have a lower drag, more efficient than other species, indicating more efficient force.
To swim at the same distance to other sea turtles of the comparable size and weight, leatherback turtles spend on average 20% less energy. Among all the deep diving animals, the champions have always been assumed to be the marine mammals, the great whales, and airless seals. Our recent investigations, however, suggest that leatherback sea turtles may also be ranked among the ocean's greatest air-breathing dive reptiles.
While mirroring the dives of the leatherback sea turtles near St. Croix in the U.S. Virgin Islands, scientists recorded a 650-pound female that sank to more than 3,330 feet and remained there for 37 minutes. High pressure also poses a challenge to the deep diver in terms of strong forces that could compress the chest, causing broken bones or tissue damage. Unlike its hard-shelled relatives, leatherbacks has a softer shell made up from widely separated ribs embedded in thick tissue, and the whole structure is overlaid with leathery skin.
How do the deep diving animals, whales, seals, penguins, and leatherback turtles avoid decompression sickness and other hazards while they dive to great depths, even sleep for a long period of time? Many of the deepest diving marine mammals have small lungs and forcefully exhale before diving. In addition to reducing the buoyancy so that they can dive more easily, this severely limits the amount of nitrogen in their bloodstream. One reason the leatherback ranges so far may be its specialised diet.
This giant of the sea feeds mainly on jellyfish full of high protein and other useful minerals they require during the day. Although the variety of jellyfish and related prey are abundant, they are eaten by few other animals. As one might suspect, a life spent eating mostly jellyfish requires some special adaptions to make the job easier.
During the 1984 and 1985 nesting seasons, with the assistance of scientists, attached recorders to 10 female leatherbacks that just laid eggs. As a result, we are able to monitor their pattern of migration in the Atlantic Ocean when they return to the sea. Some of the longest travel recorded for many animals have been made by this marine turtle.
In 1970, a female leatherback stagged when she nested in Surimi on the northeast coast of South America. Less than one year later, she was captured off the coast of Ghana, West Africa, having travelled 3,700 miles across the Atlantic Ocean. Upon returning to the surface, the turtle changed her quick breath and immediately headed straight down again.
Little or no time was given to sleep or rest. We then began to track and tag the turtles when they swam back to the surface. On closer examination, we noticed a difference in dives depending on the time of the day.
Night dives were shallower with less in-depth than day dives. Leatherbacks are such swimmers that they rarely stop moving, a behaviour that has made it impossible to keep them in captivity. The front flippers are more than half the length of the turtle's body and generate power from huge muscles, which can account for 30% of the animal's total body weight.
Since leatherbacks cannot easily be studied in captivity, researchers have been developing methods of studying them at sea. They use the recorder, an instrument capable of recording location and depth in sea. Developed by Gerald Kuhlman of the Psychological Research Laboratory, the device has been used to study diving marine animals.
While they keep diving, scientists soon realised that the turtles were probably costing much of their energy to follow their food source. In tropical waters, jellyfish are most common at great depths, in a biological zone called the deep scattering layer. Discovered shortly after the development of the sonar, this zone consists of a layer of zooplankton that hovers below 1,800 feet during the day and migrates to the surface at night.