Sea Turtles

  by Krysta Cardinale

Sea turtles are reptiles that have ancestors who evolved on land and then returned to the oceans to live. All species of turtles have a hard outer shell that protects them from enemies. They are also all known for their slow speed. Unlike land turtles, sea turtles lack the ability to retract their heads into their shells. In deeper comparison to other turtles, the sea turtle has adapted well to life in the sea. Their shells are very light, their front and rear legs are flippers, and their shape is relatively streamlined. They have a high endurance capable of swimming long distances at speeds up to 35mph.

Much like dolphins, whales, and seals, sea turtles have the ability to hold their breath for long periods of time. They actually store oxygen in their lungs and tissues during immersion in water. This faculty is common to most air-breathing creatures in contrast to fish, which extract and breathe oxygen directly from the water. In addition to this feature, sea turtles have developed the salt gland to rid their bodies of the salty composition of the seas. This salt gland is located just behind the ear, and sheds this excess salt as though it was crying.

Sea turtles are also known for their extraordinary sense of time and location. It is believed that they can actually sense the earth’s magnetic fields. They can live close to 200 years. Sea turtles have a tendency to return to the nesting grounds they were born on when it is time for them to lay eggs. They lay their eggs on coastal beaches at nighttime. The incubation period usually lasts about two months, then the baby sea turtles hatch and make their way to the ocean. This species used to have populations ranging in the thousands, but now due to egg poaching, hunting, getting caught in fishing nets, and natural predators many species of sea turtles are considered endangered.

Types of Sea Turtles

There are seven different species of sea turtles. The different species are distinguished by their size, the scales on their head, and the color and shape of the plates on their shells. These plates are called costal or vertebral scutes. The vertebral scutes are the plates down the center of the shell, and the costal scutes are on along the outside. These seven species consist of Kemp's Ridley, Flatback, Olive Ridley, Leatherback, Loggerhead, Hawksbill, and Green Sea Turtle.

Kemp’s Ridley Sea Turtle

The Kemp’s Ridley is the smallest species of sea turtle, the adult reaching weights from 75-100 pounds. It can be found mainly in the Gulf of Mexico, however some juveniles have been seen as far north as Cape Cod, Massachusetts. This turtle typically consumes dead fish and shrimp, and crabs. The Kemp’s Ridley changes color as it matures. When it is a baby sea turtle, the Kemp’s Ridley is gray black. As the turtle matures, the shell becomes an olive-green to a gray-green color, the scales become a creamy white, and the underbelly shell, or plastron, turns a yellow-green color. This type of turtle has an oval or heart-like shaped shell as an adult. Since the Kemp’s Ridley is typically found in shallow waters, lagoons, and bays they are often caught in fishing nets or hooks by sporting fishermen. This species has a unique nesting procedure. All the females of the Kemp’s Ridley species lay their eggs on the same beach in Mexico. This event has become known as the “arribada.” In 1947, approximately 40,000 Kemp’s Ridley sea turtles came onto a five mile strip of Mexican beach and laid their eggs. Most females nest from two to three times a year from mid-April to mid-August, with a nest size of about 100 eggs. The species has become endangered, and only a few hundred can now be seen in an arribada. Due to heavy exploitation of their eggs and meat in the 1960s, in combination with being caught in fishing occurrences, usually shrimp trawls, the numbers have dropped drastically. In recent years, the Kemp’s Ridley Sea Turtle seems to be making a comeback thanks to protection of their nesting grounds and new fishing regulations.

Flatback Sea Turtle

This type of turtle gets its name from the significantly flattened shell it possesses. The Flatback Sea Turtle has a yellow-gray or green-gray oval upper shell (carapace). The plastron is a pale yellow color usually with a darker yellow band. There is also a pair of prefrontal scales on the head of this turtle. The Flatback turtle ranges in size up to 198 pounds, and can be found in the Gulf of Papua New Guinea, inhabits shallow grassy waters or coral reefs. It typically eats various crustaceans and sea cucumbers. Flatback sea turtles have been seen laying eggs in Northern Australia year-round; however their typical season is from October to February. The Flatback nests up to four times a season with a nest size of 50 large eggs. They only need a period of 13-18 days in between their nesting’s.

Olive Ridley Sea Turtle

The Olive Ridley, like its cousin the Kemp’s Ridley, is a small sea turtle only reaching a maximum weight of 100 pounds. Its overall color is olive green. The Olive Ridley is naturally found in tropical coastal bays and estuaries. In the Eastern Pacific Ocean, it is found from Southern California to Northern Chile. This type of turtle can also be seen on the Atlantic shore of West Africa and South America, as well as in the Indian Ocean. The only major difference between the Olive Ridley and the Kemp’s Ridley sea turtles would be that the Kemp’s Ridley has 5 costal and 5 vertebral scutes on its shell, whereas the Olive Ridley has from 5-9 costal and 7 vertebral scutes. The Olive Ridley also nests in “arribadas” with a nest size over 110 eggs. The exploitation of the Olive Ridley for its eggs, meat, and leather has dropped its population size to dangerously low levels. It has been considered endangered in Mexico since the early 1990s, and threatened in the rest of the world.

Leatherback Sea Turtle

The leatherback is the largest of the sea turtles. It can reach such enormous sizes from 650-1,200 pounds and lengths from 6-8 feet. A few Leatherbacks have actually been reported as reaching weights of 2,000 pounds. These turtles are normally found in tropical or subtropical waters, but they have been spotted as far north as Nova Scotia. Leatherback turtles primarily feed on jelly-fish only. Unlike other sea turtles, the Leatherback lacks the hard bone-like shell. Instead it has a softer leather like shell with bone-like plates imbedded in it. This type turtle is distinctively triangular in shape, and is dark brown to black in color with white spots. The Leatherback species is known to be highly active in its migration throughout deep water. These turtles are made up of a high fat content that insulates them in cold waters, giving them the ability to make dives up to 4,265 feet deep. The Leatherback turtle has the hardest time coming ashore, and its nesting is done mainly throughout the month of December. The females can produce nests from 50-180 eggs six to seven times a year with a ten day interval in between. Their major nesting grounds include the coast of Florida, Gulf of Mexico shore of Mexico, the Pacific Coast of Mexico, and Costa Rica. The Leatherback sea turtle is considered an endangered species due to the harvesting of millions of its eggs and the killing of large numbers of nesting females.

Loggerhead Sea Turtle

This species of turtle was given its name for its strong jaws and relatively large head. The Loggerhead sea turtle can grow to be 150-500 pounds and 4 feet long in size. They have a brown to reddish-brown carapace (upper shell), and a creamy yellow lower shell. Their skin generally ranges from brown to yellow, and they have deep rusty brown scales on the top of their heads. This type of turtle typically eats crabs, jelly-fish, shellfish, and sponges. The Loggerhead sticks to warm waters in lagoons, bays, and ship canals. Some Loggerhead sea turtles actually bury themselves in the mud during the colder winter months. Their known nesting grounds are mostly found along the Atlantic coasts of the United States, Mexico, South America, Africa, Europe, and islands in the Atlantic Ocean. Loggerhead sea turtles nest between the months of April and July. They usually lay eggs in numbers of 105-120 at a time, several times a year. The Loggerhead sea turtle is considered a threatened species. Raccoons are known as a major egg predator. This species is also known for its rich color, so it is often killed to make leather accessories such as boots and handbags. Another problem for the Loggerhead population is that the nesting grounds can be located next to coastal highways. Baby sea turtles can often get confused and wander onto the highways where they get killed.

Hawksbill Sea Turtle

The Hawksbill is a mid-sized sea turtle ranging in size from 95-165 pounds. In comparison to others, the Hawksbill sea turtle is slender in appearance with a long narrow head and hawk-like beak (hence its name). This species has a rich reddish brown to dark-brown spotted carapace. The scutes on a Hawksbill sea turtle’s shell are unlike any other sea turtle. The scutes actually overlap with the ones behind it all the way down their shell. The Hawksbill likes warm tropical or subtropical shallow waters throughout all oceans. They can usually be found in coral reefs, lagoons, and rocky areas due to the fact they primarily feed on sponges. Hawksbill turtles only nest every second or third year. They make nests consisting of about 160 eggs several times that particular year. The Hawksbill sea turtle is considered an endangered species because it is sought after for its beautifully colored shell for expensive products such as jewelry.

Green Sea Turtle

This type of turtle is named after its green colored fatty areas. The Green sea turtle grows to be about 4 feet in length and 250-500 pounds in size. They are typically reddish-brown to light brown with darker spots colored shells. This species is separated from other sea turtles by its two, distinctly noticeable, oval shaped scales between its eyes. The Green sea turtle is known to travel long distances in the warmer waters. They are generally found in shallower waters like in reefs and lagoons. Green sea turtles primarily eat different sea grasses and algae. This species only lays eggs every 2-4 years from June through October. Females lay from 75-150 eggs at a time, and can do this up to seven times a year. Green sea turtles are considered an endangered species in the United States and Mexico, and are threatened every where else. This species is often made into a soup and considered a delicacy through out the world.