Green Sea Turtles
- Is the largest hard-shelled sea turtle.
- Receives its name from the color of its body fat, which turns green as a result of an algae-based diet.
- Adults average 3.5-4 feet in length. The largest green turtle ever found was 5 feet (152 cm) in length and 871 pounds (395 kg). Adults weigh between 300 – 400 pounds (136-180 kg).
- Easily recognizable because of its distinct pair of prefrontal scales located in front of the eyes.
- The carapace color varies from pale to very dark green and plain to very brilliant yellow, with brown and green tones and radiating stripes.
- Found in all of the world’s temperate and tropical waters.
- Eating primarily seagrass and algae, it is only turtle that is strictly herbivorous as an adult.
- Nests at intervals of two, three, or more years.
- Migrates long distances to return to natal beach.
- Is in danger of extinction primarily due to commercial fishing and human harvesting of turtles and their eggs.
©Robert Van Damm
Migration of Green Turtles
Unlike other species, Green Turtles are found in all temperate and tropical waters throughout the world. Green turtles spend most of their lives in the ocean near the coastline and around islands. They often live in bays and protected shores, especially in areas with seagrass beds. Nesting green turtles are thought to return to the same beach where they were born. In order to return to their natal beaches, Green turtles migrate long distances from their feeding areas.
The Reproductive Cycle and Nesting
Nesting occurs in intervals of two, three or more years, but wide year-to-year fluctuations are reported. Generally, the females nest 3-5 times each season. Green turtles only nest during the night, when the female climbs out of the ocean to an area in the upper beach. After digging a pit with her rear flippers to carve out a bottle-shaped burrow, she lays her eggs. On average, the female lays 115 leathery-skinned eggs. After burying the eggs with sand, the female turtle returns to the ocean. The eggs incubate for around 60 days before the hatchlings emerge. It is estimated that there are about 88,520 nesting females in the world.
Like other hatchlings, Green turtles hatch with the aid of an egg tooth, or a temporary protrusion attached to the beak that allows the hatchling to crack through the shell. Weighing about one ounce each, the hatchlings emerge from the nest as a group in a process that lasts several days. Hatchlings follow the brightest horizon to the ocean, where they stay for at least a year before returning to land.
The Green Turtle is listed as Endangered under the U.S. Federal Endangered Species Act, meaning that it is in danger of extinction within the foreseeable future. The International Union for Conservation of Nature and Natural Resources also listed the Green Turtle as endangered, predicting that it will face a very high risk of extinction in the foreseeable future. There are many factors contributing their endangered status. Although illegal in most countries, Green turtles are hunted relentlessly on the beach as well as on the ocean. and are often sold openly in many towns. The fishing and shrimp industries contribute to the decline in their population by not using Turtle Excluder Devices (TEDS), and still using detrimental practices such as longline fishing or gill nets. In addition, coastal developments and environmental degradation play a large factor in the Green turtles’ fate.
Green Turtles and the Ecosystem
Green turtles consume large quantities of seagrass. Studies in Caribbean waters indicate that seagrass may support as much as 10,000,000 kg of Green turtles per square kilometer. Grazing by green turtles has significant effects on the structure and nutrient cycling in these systems (Eckert).
Areas cropped by Green turtles readily grow fresh grasses. The higher nutritional quality of this new vegetation subsequently, draws and sustains a wide variety of oceanic life. Scientists are concerned that declining populations of Green turtles will create ecological imbalances that could have long-term effects on the health of our oceans (Aragones).
Just how devastating would the loss of the Green turtle be to our planet’s seas? Scientists can speculate, but no one can really know the full impact until it is too late. It is reasonable to say; however, that the loss of such an ancient and globally prevalent creature would create a substantial alteration of the oceanic environment.
We appreciate gathering some of our data from the following resources. Many of these websites have additional pages with links that will provide more detailed information about sea turtles:
Aragones, Lemnuel V, "A Review of the Role of the Green Turtle in Tropical Seagrass Ecosystems."
Caribbean Conservation Corporation: http://www.cccturtle.org/green.htm
Eckert, Scott PhD: Safeguarding Pacific Sea Turtles in the Oceanic Commons