Let’s start of with one questions, why is it called the green sea turtle? I have seen these numerous times while scuba diving both on boats and off the shore and they certainly aren’t particularly green. Did you know it was named for the green color of the fat under its shell that is found around their internal organs? In fact green turtles are black-brown or greenish yellow in color. Well that explains a lot and I feel super stupid right now. Most of the ones we sea off the shore dives in Lauderdale by the Sea and Vero beach have been green sea turtles.
There are two types of green turtles normally found off the shores of Europe and North America, and the Eastern Pacific green turtle, which has been found in coastal waters from Alaska to Chile.(In some areas, the Pacific green turtle is also called the black sea turtle but I am going to focus on what we see here in Florida).
They live in tropical and subtropical waters. They can be found along the Atlantic coast of the island and the continent, the Pacific Ocean and Indian Ocean. Their populations are also known in the warm ocean waters in the Mediterranean.
Green sea turtles breathe with lungs. Just like humans, they need oxygen from the air to breathe. At sea, they usually go to the surface to get oxygen. Interestingly, their lungs have the ability to store air in a long time. As a result, the green turtle can be under water for a long time. Female Green sea turtles have been known to travel more than 2600 miles on their migration between food and nesting beaches. Green sea turtles are one of the oldest living creatures on earth. They were around during the time of the dinosaurs. Their size is believed to have reached half the size of dinosaurs at that time. After the process of evolution, their size becomes smaller, as you see now.
The green sea turtle is the second most common turtle in Florida waters. They mainly stay near the coastline and around islands and live in bays and protected shores, especially in areas with seagrass beds. They are rarely observed in the open ocean. Adult green sea turtles prefer coral reefs, sea grass beds and mangroves, while hatchlings and juveniles live farther from shore. Green sea turtles are the only herbivorous (plant-eating) sea turtles. They feed on seagrass and algae in shallow areas throughout the Gulf as adults. However, it should be remembered that young green sea turtles are carnivorous animals. They eat jellyfish and other invertebrates. They also enjoy squids, crabs and other small sea creatures. The lower jaw on an adult is serrated to help cut the seagrasses it eats.
The green sea turtle has fabulous symbiosis with the fish on the reef who feed off the algae found on his shell.
Adults are 3 to 4 feet in carapace length (83 – 114 cm). The green turtle is the largest of the Cheloniidae family. The largest green turtle ever found was 5 feet (152 cm) in length and 871 pounds (395 kg).
The carapace (or shell) is oval when viewed from above, and the head is relatively small and blunt. They are easily distinguished from other sea turtles because they have a single pair of scales in front of its eyes, rather than two pairs as found on other sea turtles. Carapace is bony without ridges and has large, non-overlapping, scutes (scales) present with only 4 lateral scutes. Its carapace is composed of five central scutes flanked by four pairs of lateral scutes. Underneath, the green turtle has four pairs of infra-marginal scutes covering the area between the turtle’s underbody and its shell.
Green Sea Turtle shell
Body is nearly oval and is more depressed (flattened) compared to Pacific green turtles. The head in proportion to it’s body appears small. The carapace of the turtle has various color patterns that change over time. Hatchlings, like those of other marine turtles, have mostly black carapaces and light-colored underbellies. Underneath, the turtle’s is hued yellow. Limbs are dark-colored and lined with yellow, and are usually marked with a large dark brown spot in the center of each appendage. All flippers have 1 visible claw. Hatchlings are dark-brown or nearly black with a white underneath and white flipper margins.
The sea turtle lifespan is unknown but believed to be around 80 years. Sexual maturity occurs anywhere between 20-50 years. For this reason, it is hard to repopulate declining numbers but I do wonder with the current efforts to save turtles is this will rebound for my grandchildren’s generation.
The females return to the same beaches where they were born. This is called natal” beaches. They do so approximately every 2-4 years to lay eggs, generally in the summer months. While nesting season varies from location to location, in the southeastern U.S., females generally nest in the summer between June and September; peak nesting occurs in June and July. During the nesting season, females nest at approximately two-week intervals. Green sea turtles nest only at night. The female must pull herself out of the water and all the way to the dry sand of the upper beach using only her front flippers. This is a difficult task as her front limbs have been modified into highly effective swimming flippers, and do not support the bulk of her weight in the sand. Reaching the upper portion of the beach, she uses her front flippers to dig a broad pit in the sand and her rear flippers to delicately carve out a bottle-shaped burrow. She then lays her egg clutch, which consists of approximately 135 leathery-skinned eggs here in Florida, Next she covers them carefully with sand. Lastly, she buries the pit entirely to disguise the location of her nest. Her parenting job completed, she returns to the sea, leaving her young to fend for themselves.They lay an average of five nests, or “clutches.” Hutchinson Island, close to me here in Florida is one of the largest nesting areas in Florida.
Green sea turtle eggs take about two months to incubate. Studies indicate that the temperature of the eggs during incubation influences the sex of baby sea turtles. Lower temperatures tend to produce males, while higher temperatures tend to produce females. The baby turtles are able to break through the eggshell and hatch by chipping away at the shell with a structure called an egg tooth, a temporary hard protuberance on their beaks. After hatching, the tiny one-ounce turtles take a number of days to dig their way out of their nest. Emerging from the nest must be a group effort as one hatching would not be able to escape by itself. Working together, the little turtles scrape away the roof of the nest until they reach about an inch away from the surface of the beach. The hatchlings nearest to the surface stop their digging if the sand feels hot, indicating that it may be daytime. They wait to resume digging until the sand feels cool, indicating that it is night, and safer to emerge by avoiding the harsh rays of the sun and possibly, predatory birds. Once out of the nest, the juvie turtles find their way to the ocean, by heading towards the brightest horizon. This is why artificial lights on nesting beaches can mean death to the young turtles as they may confuse them and cause the them to lose their way. When they find their way to the ocean, the baby turtles must swim continuously for the next day and a half to two days. The young turtles remain at sea and do not come inshore until at least one year later.
So next time you see a dark bown or black spotted turtle while diving or snorkeling, look at his eyes. Does it have one bony plate or two? Hopefully I am going to enjoy swimming with some of my sea turtle friends in LDBS this weekend!
Danielle's Dives Blog 