Green Sea Turtle: Named for Its Fat, Not Its Scales or Shell

Green sea turtles are among the largest marine turtles, with adults growing up to 4 feet long (1.22 meters) and weighing an average of 350 pounds (158.8 kilograms).

Their oval-shaped, smooth carapace varies in color from shades of brown and olive green to black, depending on their region. Beneath their shell, their skin is often light yellow or white, contrasting with the greenish fat layer that gives them their name.

Juvenile green turtles are smaller and have more vibrant shell patterns, which fade as they mature.

Unlike some other sea turtles, adult green turtles have a single pair of prefrontal scales on their heads (in front of their eyes), a key identifier. Their paddle-like flippers allow them to glide gracefully through their marine turtle habitat, from shallow reefs to open ocean waters.

Green sea turtles (Chelonia mydas) are often categorized into different regional populations, each adapted to its specific environment.

One notable group is the black sea turtle (Chelonia mydas agassizii), which primarily inhabits the eastern Pacific Ocean, particularly along the coasts of Mexico, Central America and the Galapagos Islands. This group is distinguished by its darker shell coloration, smaller size and differences in body shape compared to other green turtle populations.

In addition to the black sea turtle, other significant populations include those in the Atlantic Ocean, particularly around the Caribbean, Florida and the West African coast.

Green sea turtles in the Indo-Pacific region — including populations around Southeast Asia, Australia and the Indian Ocean islands — also show distinct physical and behavioral adaptations. These regional variations are influenced by differences in climate, diet and nesting environments.

While the black sea turtle is sometimes referred to as a subspecies, it is generally considered a regional morphotype rather than a distinct subspecies. This classification reflects the broader variability within Chelonia mydas, which exhibits remarkable adaptability to diverse ecosystems.

Green sea turtles are generally solitary creatures that spend most of their lives alone in vast oceans. However, they gather near nesting beaches in large numbers during the breeding season. This is when green turtles nest in synchrony, with females returning to the same beach where they were born.

While on land, females dig deep nests and lay around 128 eggs per clutch. Once the nesting process is complete, they return to the sea, leaving the hatchlings to fend for themselves.

Unlike other species that may exhibit some social tendencies, green turtles remain largely independent throughout their lives.

The life cycle of green sea turtles begins on sandy beaches, where females dig nests and lay their eggs during the nesting season. Green turtle nesting sites are often located on tropical coastlines (like those around Florida and Costa Rica), with females returning to their natal beaches every two to four years.

Each clutch of eggs takes about 60 days to hatch, depending on sand temperature. Newly hatched sea turtles, called hatchlings, face immediate danger as they scramble to the ocean, avoiding predators like birds, crabs and fish.

Those that make it to the water enter a "lost years" phase, drifting in ocean currents and growing steadily.

Juvenile green turtles eventually settle in coastal habitats, maturing over 25 to 30 years before returning to nesting beaches to lay their own eggs. With a lifespan of 60 to 70 years in the wild, green turtles play a long-term role in maintaining marine ecosystems.

Adult sea turtles are highly adaptable and inhabit many marine environments. They are commonly found in tropical and subtropical waters, especially near coral reefs, seagrass beds and mangrove estuaries. These habitats provide critical feeding and resting areas for the turtles.

Juvenile green turtles often live in pelagic zones (the open ocean, away from the coast and seabed), drifting with ocean currents until they mature and migrate to nearshore areas.

The health of marine turtle habitats is vital for their survival, as habitat degradation poses a significant threat to green sea turtles and other marine species.

Green sea turtle diets fluctuate over their lifetime. Juvenile green turtles are omnivorous, feeding on a mix of algae, small invertebrates (such as jellyfish) and seagrass. As they grow, they transition to an entirely herbivorous diet, grazing on seagrass and algae.

This diet helps maintain the health of their marine turtle habitat. Adult green turtles promote seagrass growth and prevent overgrowth by trimming seagrass meadows, benefiting entire ecosystems.

Their diet is also the reason for their distinctive greenish fat, which sets them apart from other sea turtles.

Green sea turtles are listed as an endangered species due to numerous threats, including habitat destruction, poaching, climate change and bycatch — the unintentional capture of non-target species during fishing activities during fishing.

Coastal development has destroyed many nesting beaches while rising sea levels and warmer sands affect hatchling sex ratios and survival rates.

Efforts to protect sea turtles have gained momentum through initiatives like habitat restoration, protected nesting sites and international agreements. Organizations and governments work tirelessly to conserve marine turtle habitats and promote awareness about these incredible creatures.

By supporting these efforts, we can ensure that green sea turtles continue to thrive in the oceans they help sustain.

We created this article in conjunction with AI technology, then made sure it was fact-checked and edited by a HowStuffWorks editor.