Common Name
Green Sea Turtle

Scientific Name
Chelonia mydas

Description
Green Sea Turtles are easily distinguished from other sea turtles because they have a single pair of prefrontal scales (scales in front of its eyes), rather than two pairs as found on other sea turtles. Their head is small and round with a serrated jaw. The carapace is bony without ridges and has large, non-overlapping, scutes present with only 4 lateral scutes. Their body is teardrop shaped and more flattened compared to the Pacific Green Sea Turtles (aka Black Sea Turtles, often classified as a sub-species of the Green Sea Turtle). Their colour varies from pale to very dark green and plain to very brilliant yellow, brown and green tones with radiating stripes. However, their name is given to the colour of their fat (as a result of their diet), not their carapace. The plastron varies from white, dirty white or yellowish in the Atlantic populations to dark grey-bluish-green in the Pacific populations. Hatchlings are dark-brown or nearly black with a white underneath and white flipper margins. All flippers have 1 visible claw each.

Size
Adults measure between 0.8 and 1.2 metres in carapace length.
The Green Sea Turtle is the second largest after the Leatherback and the largest of the Cheloniidae family. The largest Green Sea Turtle ever found was 1.52 metres in length and 395 kilograms.

Weight
Adults weigh between 110 and 225 kilograms.

Lifespan
Green Sea Turtles are estimated to live between 70 and 80 years or more.

Diet
The Green Sea Turtles’ diet changes significantly during their life. When less than 20-25 centimetres in length, they eat worms, young crustaceans, aquatic insects, jellyfish, sea grass and algae. Once they reach 20-25 centimetres in length, they mostly eat sea grass, seaweed, algae, mangrove leaves and shoots, and other forms of marine plant life. The Green Sea Turtle is the only sea turtle that is strictly herbivorous as an adult, giving their fat a green colour, hence their name. Their jaws are finely serrated which aids them in tearing vegetation and scraping algae off hard surfaces.

Range
Green Sea Turtles are found in all temperate and tropical waters throughout the world (including the Pacific population).

Habitat
Green Sea Turtles mainly stay near the coastline and around islands and live in bays and protected shores, especially in areas with abundant algae and sea grass beds. Rarely are they observed in the open ocean. Juvenile Green Sea Turtles disperse into pelagic and neritic habitats along the continental shelf where they feed on a wider diet including invertebrates before returning to coastal waters and adopting a mostly herbivorous diet as adults.

Nesting

• Reproduction Interval: 2 years (with wide year-to-year fluctuations in numbers of nesting females)
• Clutches Per Season: 3-5 clutches
• Clutch Size: 115 eggs
• Nest Incubation Period: 60 days
• Sexual Maturity: 20-50 years

Green Sea Turtles (including the Pacific population) have the most numerous and widely dispersed nesting sites of all sea turtle species in over 80 countries, but major nesting beaches include Tortuguero (Costa Rica), Oman, Florida, and Raine Island (Australia) where thousands of turtles nest each night during peak nesting season. Nearly all Hawaiian Green Sea Turtles migrate to nest at French Frigate Shoals in the Northwestern Hawaiian Islands (NWHI). The NWHI are designated as a refuge and are restricted to scientific research only. Other nesting sites include Guam, American Samoa, Suriname, Georgia, South Carolina, North Carolina, Puerto Rico and the US Virgin Islands. Green Sea Turtles nest in highly diverse types of habitats, including archipelagos, isolated coral atolls and mainland beaches, in all tropical and subtropical oceans.

Population Estimates
Between 85,000 and 90,000 nesting females.

Status
International: Listed as Endangered (facing a very high risk of extinction in the wild in the near future) by the International Union for Conservation of Nature and Natural Resources in 1982.
USA: Downlisted to Threatened (likely to become endangered, in danger of extinction, within the foreseeable future) in April 2016 under the Federal US Endangered Species Act of 1973. Originally listed as  Endangered in 1978.

Interesting Facts

• The Green Sea Turtle is the second largest after the Leatherback and the largest of the Cheloniidae family.
• Green Sea Turtles have the most numerous and widely dispersed as well as highly diverse nesting sites of all sea turtle species.
• Adult Greens leave symmetrical tracks with an average width of 100-130 centimetres when they crawl up onto the beach. These are created when the turtle moves both front flippers forward simultaneously.
• The Green Sea Turtle is the only sea turtle that is strictly herbivorous as an adult. Their jaws are finely serrated which aids them in tearing vegetation and scraping algae off hard surfaces.
• Their name comes from the colour of their fat (as a result of their diet), not their carapace.
• Green Sea Turtles are believed to aid the health of sea grass beds and associated microhabitats by grazing the beds and taking the tops off leaf blades, while avoiding the roots; thus the sea grass will grow back faster and healthier. This also aids in the carbon uptake of sea grasses.
• The population of Green Sea Turtles in the Caribbean is estimated to once have been as high as 500 million individuals.
• Green Sea Turtles were once highly sought after their body fat, a key ingredient in ‘green turtle soup’. Despite it becoming illegal to trade them in many parts of the world, Green Sea Turtles and their eggs continue to be consumed.
• Green Sea Turtles were once a source of food for European explorers to the New World and helped crews navigate around islands at night by the increased volume of their aggregated breathing.
• Pacific Green Sea Turtles (also known as the Black Sea Turtles) are a sub-species of the Green Sea Turtle, however, some researchers believe they may be a separate species. Their skin pigmentation is overall darker than other Green Sea Turtles and they lay fewer eggs. They are also smaller and their carapace not as flat.

References
ECOMAR: Species
NOAA Fisheries: Green Sea Turtle
Sea Turtle Conservancy: Green Sea Turtle
See Turtles: Green Sea Turtle
SWOT: Green Sea Turtle
Upwell: Green Sea Turtle

<< Sea Turtles