Green sea turtle. Photo: NOAA Pacific Islands Fisheries Science Center
Green sea turtle. Photo: NOAA Pacific Islands Fisheries Science Center
About the Species
The green sea turtle is the largest hard-shelled sea turtle. They are unique among sea turtles in that they are herbivores, eating mostly seagrasses and algae. This diet is what gives their fat a greenish color (not their shells), which is where their name comes from.
Green turtles are found throughout the world. They nest in over 80 countries and live in the coastal areas of more than 140 countries. Historically, green turtles were exploited for their fat, meat and eggs, causing global population declines. Many countries, including the United States, prohibit the killing of sea turtles and collection of their eggs. However, in some areas, the killing of green turtles for their meat or to supply shells to the wildlife trafficking trade remains a threat to their recovery. Bycatch in commercial and recreational fishing gear, vessel strikes, loss of nesting habitat from coastal development, and climate change are the biggest threats facing green turtles.
NOAA Fisheries and our partners are dedicated to protecting and recovering green turtle populations worldwide. We use a variety of innovative techniques to study, protect, and recover these threatened and endangered populations. We engage our partners as we develop measures and recovery plans that foster the conservation and recovery of green turtles and their habitats. And we fund research, monitoring, and conservation projects to implement priorities outlined in recovery plans.
Population Status
Green turtles are found worldwide with 11 distinct population segments (DPS) listed under the Endangered Species Act. The largest green turtle nesting populations in the world are found at:
- Tortuguero on the Caribbean coast of Costa Rica—30,000 females nest per season (on average).
- Raine Island on the Great Barrier Reef in Australia—During a peak nesting season, up to 60,000 females nest on this island and the surrounding reef.
Green turtles nest in over 80 countries, but in the United States, nesting green turtles are primarily found in the Hawaiian Islands, U.S. Pacific Island territories (Guam, the Commonwealth of the Northern Mariana Islands, and American Samoa), Puerto Rico, the Virgin Islands, and Florida. Nesting also occurs annually in Georgia, South Carolina, North Carolina, and Texas.
The 2015 ESA status review of the green sea turtle provides additional information for this species.
Protected Status
ESA Endangered
- Central South Pacific DPS
ESA Endangered
ESA Endangered - Foreign
ESA Threatened
- Central North Pacific DPS
ESA Threatened
ESA Threatened
ESA Threatened
ESA Threatened - Foreign
- East Indian-West Pacific DPS
ESA Threatened - Foreign
ESA Threatened - Foreign
ESA Threatened - Foreign
CITES Appendix I
Appearance
Green turtles are the largest of all the hard-shelled sea turtles, but have a comparatively small head. A typical adult is 3 to 4 feet long and weighs 300 to 350 pounds. They have dark brown, grey, or olive colored shells and a much lighter, yellow-to-white underside. Their shells have five scutes running down the middle and four scutes on each side. Other distinct characteristics of the green turtle are their serrated beak on the lower jaws and two large scales located between the eyes.
Behavior and Diet
Green turtles, like all sea turtles, are reptiles and must surface to breathe and lay their eggs on land. Green turtles migrate hundreds to thousands of kilometers each way between their foraging grounds and nesting beaches. They are solitary, night-time nesters.
The life history of green turtles involves a series of stages of development from hatchling to adult. After emerging from the nest, hatchlings swim to offshore areas, where they live for several years in pelagic habitat. Juveniles eventually leave the open ocean habitat and travel to nearshore foraging grounds in shallow coastal habitats, where they mature to adulthood and spend the remainder of their lives. Adults migrate every 2 to 5 years from their coastal foraging areas to the waters off the nesting beaches where they originally hatched to reproduce.
Green turtles are the only herbivorous species of sea turtle. Their diet mainly consists of algae and seagrasses, though they may also forage on sponges, invertebrates, and discarded fish. The East Pacific green turtle tends to eat more animal prey than other populations. Prior to recruiting to nearshore foraging areas, pelagic juveniles forage on plant and animal life found in oceanic drift communities (such as pelagic Sargassum communities).
Where They Live
Green turtles are found worldwide primarily in subtropical and temperate regions of the Atlantic, Pacific, and Indian Oceans, and in the Mediterranean Sea.
In U.S. Atlantic and Gulf of Mexico waters, green turtles are found in inshore and nearshore waters from Texas to Maine, the U.S. Virgin Islands, and Puerto Rico. Important feeding areas in Florida include the Indian River Lagoon, the Florida Keys, Florida Bay, the Dry Tortugas, Homosassa, Crystal River, Cedar Key, and St. Joseph Bay.
In the eastern North Pacific, green turtles have been sighted as far north as southern Alaska, but most commonly occur from southern California to northwestern Mexico. Elsewhere in the U.S. Pacific, green turtles occur in Hawaii, American Samoa, Guam, and the Commonwealth of the Northern Mariana Islands.
Green turtles occur in many countries, making it critical to work together for their protection and recovery.
World map providing approximate representation of the green turtle's range.
Lifespan & Reproduction
Green turtles are long-lived and could live for at least 70 years or more. Female green turtles reach maturity at 25 to 35 years. Every 2 to 5 years they undertake reproductive migrations and return to nest on a beach in the general area where they hatched decades earlier.
In the United States, the breeding season begins in late spring. Males mate with females on foraging grounds, along migratory pathways, and off nesting beaches. Green turtles lay about 110 eggs per nest and will nest every 2 weeks over several months before leaving the nesting area and returning to their foraging grounds.
After about two months incubating in the warm sand, the eggs hatch and the hatchlings make their way to the water. Hatchlings orient seaward by moving away from the darkest silhouette of the landward dune or vegetation to crawl towards the brightest horizon. On undeveloped beaches, this is toward the open horizon over the ocean.
Threats
Bycatch in Fishing Gear
A primary threat to sea turtles is their unintended capture in fishing gear which can result in drowning or cause injuries that lead to death or debilitation (for example, swallowing hooks, or flipper entanglement). The term for this unintended capture is bycatch. Sea turtle bycatch is a worldwide problem. The primary types of gear that result in bycatch of green turtles include trawls, gillnets, longlines, hook and line, and pot/traps.
Direct Harvest of Turtles and Eggs
Historically, green turtles were killed in extraordinarily high numbers for their fat, meat, and eggs. This led to the catastrophic global decline of the species. While illegal in the United States, killing green turtles and collecting their eggs remains legal in some countries and this can disrupt regional efforts to recover this species.
Loss and Degradation of Nesting Habitat
Coastal development and rising seas from climate change are leading to the loss of nesting beach habitat for green turtles. Shoreline hardening or armoring (e.g., seawalls) can result in the complete loss of dry sand suitable for successful nesting. Artificial lighting on and near nesting beaches can deter nesting females from coming ashore to nest and can disorient hatchlings trying to find the sea after emerging from their nests.
Vessel Strikes
Various types of watercraft can strike green turtles when they are at or near the surface resulting in injury or death. Vessel strikes are a major threat to green turtles, in particular large juveniles and adults near ports, waterways, and developed coastlines throughout their range. High boat traffic areas such as marinas and inlets present a higher risk to green turtles. Adult green turtles, in particular nesting females, are more susceptible to vessel strikes when making reproductive migrations and while they are nearshore during the nesting season.
Ocean Pollution/Marine Debris
Increasing pollution of nearshore and offshore marine habitats threatens all sea turtles and degrades their habitats. The Deepwater Horizon oil spill was the largest offshore oil spill in U.S. history and affected nesting (including nesting females, eggs, and hatchlings), small juvenile, large juvenile, and adult sea turtles throughout the Gulf of Mexico. Ingestion of marine debris is another threat to all species of sea turtles. Green turtles may ingest marine debris such as fishing line, balloons, plastic bags, floating tar or oil, and other materials discarded by humans which they can mistake for food. They may also become entangled in marine debris, including lost or discarded fishing gear, and can be killed or seriously injured.
Climate Change
For all sea turtles, a warming climate is likely to result in changes in beach morphology and higher sand temperatures, which can be lethal to eggs or alter the ratio of male and female hatchlings produced. Rising seas and storm events cause beach erosion, which may flood nests or wash them away. Changes in the temperature of the marine environment are likely to alter the abundance and distribution of food resources, leading to a shift in the migratory and foraging range and nesting season of green turtles.
Disease
Fibropapillomatosis is a disease that causes external and internal tumors in green turtles. These tumors can significantly affect their ability to swim and feed and can lead to death. The disease is most prevalent in green turtles and some evidence has linked the disease prevalence to degraded marine habitats.
Scientific Classification
| Animalia |
Chordata |
Reptilia |
Testudines |
Cheloniidae |
Chelonia |
mydas |
