Green Sea Turtle
Characteristics
Name
Green Sea Turtles get their name from the color of their body fat, which is green from the algae or grasses they eat. The Hawaiian Green Sea Turtle population, is known by its Hawaiian name Honu
History
Green Sea Turtles are reptiles whose ancestors evolved on land and returned to the sea to live. The first turtles appeared during the Triassic period, 245 to 208 million years ago. Fossils for the earliest known sea turtles appear in the Late Jurassic period, 208 to 144 million years ago. Turtles are one of the few species that watched the dinosaurs evolve and become extinct
As reptiles, sea turtles possess the following traits
They are cold-blooded, meaning they get their body heat from the
environment
They breathe air
Their skin is scale
Status
Now, scientists recognize seven species of these marine reptiles. The recognized sea turtle species are as follows: Greens, Hawksbill, Kemp's Ridley, Olive Ridley, Loggerhead, Flatback and Leatherback. The Loggerhead Sea Turtle is listed as threatened, the Flatback is listed as vulnerable, and all other species are listed as endangered. Green Sea Turtle populations of Hawaii are threatened and protected in Hawaii under state law. Populations of Green Sea Turtles off the coast of Florida and the Pacific coast of Mexico are listed as endangered. Green Sea Turtles are protected by the federal Endangered Species Act, and listed under the Convention on International Trade of Endangered Species CITES. CITES makes it illegal to import or export turtle products
Shell
In addition to their reptilian traits, all species of turtles except the Leatherback have evolved a bony outer shell, which protects them from predators. The Leatherback is the only soft-shelled sea turtle and is in a family by itself. The shell covers the dorsal (back) and ventral (belly) surfaces of a sea turtle. The dorsal portion of the shell is the carapace and is covered with scale-like structures called scutes, while the ventral portion of the shell is known as the plastron. Experts can identify species of sea turtles by the number and pattern of scutes on the carapace. The shell is considered the most highly developed protective armor of any vertebrate species. While most land turtles can retract their heads into their shells for added protection, sea turtles cannot and their heads remain out at all times
Color
Green Sea Turtles have green flesh. The carapace is olive brown to black, while the plastron is pale yellow to creamy white. The carapace is molted, variegated in color. Rarely will you find a Green Sea Turtle with a solid colored shell. Counter-shading of the shell conceals the turtle from predators, making it difficult to distinguish the dark carapace from the sea floor and the light plastron from the lighter sky
Size
Green Sea Turtles as hatchlings weigh about an ounce and have a carapace length of 2 inches. A sexually mature green sea turtle weighs 200-350 pounds with a carapace length of 2.5 feet. Adults grow to a carapace length of 3.5 feet and weigh an average of 400 pounds. One of the largest turtles that ever lived from the Late Cretaceaus period, 144 to 65 million years ago, reached a length of 9.8-13 feet
Lifespan
The lifespan of sea turtles is not known. It is believed that Green Sea Turtles reach sexual maturity around the age of 25 years and can live up to 80 years of age. The long period of maturation helps to explain why it takes turtles so many years to recover from a population decline
Shape
Sea turtles are wonderfully adapted to life in the ocean. Their shells are lighter and more streamlined than land turtles. Front and rear limbs have evolved into flippers. These flippers make sea turtles efficient and graceful swimmers, capable of swimming long distances in a short time
Adaptation
Speed & Diving
With their efficient body shape, Green Sea Turtles have been known to move through the water as fast as 35mph. When active, sea turtles swim to the surface to breathe every few minutes. When sleeping or resting, adult sea turtles can remain underwater for more than 2 hours. Turtles are capable of containing higher concentrations of carbon dioxide in their blood than most other breathing animals. This enables them to use their oxygen more efficiently and stay underwater longer. Juvenile sea turtles have not developed this ability and must sleep afloat at the water's surface
Feeding
Juvenile Green Sea Turtles are omnivorous, eating plants and animals. Their diet consists of jellyfish, shrimp, plankton and algae. Adult Green Sea Turtles are primarily herbivores, eating only plants, but they have been observed eating jellyfish and other easy-to-catch marine life. They feed on nearshore sea grass and algae pastures. Similar to cows, Green Sea Turtles depend on bacteria in their guts for digestion of plant material
Green Sea Turtle -courtesy of Kathy Streeter, New England Aquarium
Distribution and Habitat
Green Sea Turtles are distributed throughout the world's oceans between 35 degrees north and south latitude. They are found in the eastern and western hemispheres and nest on beaches throughout the Atlantic, Pacific and Indian Oceans. Green Sea Turtles enjoy warm, tropical and subtropical, shallow water near continental coasts and around islands where the sea grass is plentiful
Population
There were once several million Green Sea Turtles worldwide. Today, fewer than 200,000 nesting females are thought to remain. In Hawaii in 1992, the estimate of mature female green turtles associated with the French Frigate Shoals was set at roughly 750
Reproduction
Although Green Sea Turtles live most of their life in the ocean, adult females must return to land to lay their eggs. Upon sexual maturity, the Green Sea Turtle makes an amazing journey every two or three years to nest. They leave their feeding grounds and migrate as far as 800 miles to their nesting beaches. Biologists believe that nesting female turtles return to the same beach where they were born. This beach is called a natal beach. Males do not accompany the females, but they congregate at the breeding grounds. The males will mate with the females off the shores of the nesting beaches. The most popular nesting beaches are on French Frigate Shoals, where 90% of the Hawaiian population of Green Sea Turtles mate and lay their eggs
Green Sea Turtles-courtesy of Kathy Streeter, New England Aquarium
Green Sea Turtles nest only at night. After 7-10 weeks gestation period, the females pull themselves out of the water to the dry sand of the upper beach. Here, she uses her front flippers to dig a broad pit and her rear flippers to excavate an egg chamber. She then lays her clutch, which consists of 100-120 ping-pong sized, leathery-skinned eggs, in the egg chamber and carefully covers them with sand. Females lay up to five or six clutches of eggs in a breeding season. Once she buries the pit and disguises the location, her parenting job is complete. She returns to sea leaving her young to fend for themselves
Hatching occurs at night and begins in July after about 60 days of incubation. Studies indicate that the temperature of the eggs during incubation influences the sex of the baby sea turtles. At 82 degrees F, hatchlings are male. At 90 degrees F, hatchlings are female. Baby sea turtles are able to chip through the eggshell with a structure called an egg tooth, a temporary hard protuberance on their beaks. Working as a group, the hatchlings dig to the surface of the nest and instantly head to the water, attracted to the moon's light reflecting on the ocean's surface. Therefore, artifical lights on nesting beaches can confuse the hatchlings and cause them to lose their way. Sharks, reef fish, birds and mammals all pose predator threats upon hatchlings. Once they reach the ocean, the hatchlings remain at sea until they appear as juveniles in the near-shore waters. Only 1 or 2 out of 100 hatchlings will survive the first year
Predators
With their efficient mobility in the water and their size, adult Green Sea Turtles have only two known predators: sharks and man. Tiger sharks feed regularly on Green Sea Turtles. Man has been the greatest predator of the sea turtle, killing it for its meat, shell, and eggs while driving it almost to extinction
Other Threats
There are many threats to Green Sea Turtles beyond that of predators. Entanglement in commercial shrimp nets trap and drown more than 10,000 sea turtles each year. Litter and other marine debris can be deadly when they entangle the turtles or are mistaken for food and ingested. Nesting grounds are lost each year to coastal development, leaving females without a familiar place to lay their eggs. Noise, lights and beach obstructions disrupt nesting areas and threaten this critical part of the sea turtle's life cycle. The recent presence of a disease called fibropapilloma has affected Green Sea Turtle populations in Hawaii as well as Florida. Fibropapilloma causes the growth of large tumors on the soft tissue of the turtles. The exact cause of the disease is not known. Scientist suspect that a virus, parasite or the effect of marine pollution may be involved.
good luck
Mohamed Hassaan
