Reptiles · Sea turtles

Green Sea Turtle

Chelonia mydas (Linnaeus, 1758)

syn. Chelonia agassizii, Chelonia japonica, Chelonia mydas agassizii, Chelonia mydas mydas, Chelonia viridis, Testudo mydas

90 - 150 cm68 - 190 Kg1-200 mCITES ILeast Concern

1385

The green sea turtle, or Chelonia mydas, is a large marine reptile found in tropical and subtropical oceans worldwide. These turtles are notable for their size, reaching up to 1.5 meters (5 feet) in length, and weighing between 68-190 kg (150-419 lbs), with some individuals even heavier. Their name is derived from the green fat beneath their carapace, which can range in color from olive to almost black, particularly among certain Pacific populations.

Green sea turtles inhabit a wide variety of marine environments, including tropical waters, coastal areas, bays, and lagoons abundant with seagrass and algae. They are excellent swimmers, thanks to their streamlined bodies and flipper-like limbs, usually moving at speeds around 2.5-3 km/h (1.6-1.9 mph). As juveniles, they tend to be carnivorous, eating fish, eggs, and marine invertebrates. However, as they mature, their diet shifts predominantly to seagrasses and algae, playing a role in maintaining the health of seagrass beds by trimming blades rather than uprooting them.

These turtles typically nest on sandy beaches, where females lay eggs every 2 or 3 years. Each nest can contain 100 to 150 eggs, which incubate for approximately 45-60 days. Temperature plays a crucial role in determining the sex of the hatchlings—warmer sands generally produce females, while cooler sands produce males. Once hatched, the young turtles make a perilous journey to the ocean, facing numerous predators along the way.

Green sea turtles can live up to 90 years in the wild if they avoid predators like tiger sharks, especially near nesting sites. Unfortunately, human activities, such as habitat destruction, pollution, and illegal hunting, threaten their survival. They are classified as endangered and are protected under international law. Conservation efforts focus on protecting their nesting sites and reducing threats from human activities.

In terms of behavior, adult green sea turtles are mostly solitary and migrate long distances between feeding grounds and nesting beaches. Their reproductive system involves scramble polygamy, where males actively compete for females. Males typically have longer tails and recurved claws on their flippers to aid in mating.

Overall, green sea turtles are a critical part of marine ecosystems, contributing to the health of seagrass beds and coastal habitats while serving as indicators of ocean health. Efforts to preserve their populations are essential for both ecological balance and biodiversity.

Why it's threatened

Residential & commercial development

Housing & urban areas · Commercial & industrial areas · Tourism & recreation areas

Transportation & service corridors

Shipping lanes

Biological resource use

Intentional use (species is the target) · Intentional use: (subsistence/small scale) [harvest] · Intentional use: (large scale) [harvest] · Unintentional effects: (subsistence/small scale) [harvest] · Unintentional effects: (large scale) [harvest]

Invasive species, genes & disease

Named species

Pollution

Garbage & solid waste

Climate change & severe weather

Habitat shifting & alteration · Temperature extremes · Storms & flooding

Green Turtles are highly susceptible to anthropogenic threats including bycatch, direct take and trade (legal and illegal), collision with marine vessels, habitat loss and degradation, pollution, disease and climate change.

Direct take of turtle meat, eggs, and parts has been the most important source of mortality for Green Turtles for centuries. Although this has declined in recent years, it remains a common practice in certain cultures in many parts of the world (Bräutigam and Eckert 2006, Humber et al. 2014, Senko and Burgher et al. 2022). A recent global analysis of all reported 'illegal exploitation'—i.e., the take or trade of turtles against established law in the locality where the take occurred— produced estimates of approximately 44,000 turtles/year over the past decade, most of which were Green Turtles (Senko and Burgher et al. 2022). This analysis also suggested a decline over time in the illegal take of turtles, although a review of legal turtle harvests (Humber et al. 2014) found that at that time at least 42 countries and territories permitted direct take of turtles, and the primary species used was Green Turtles (>80%).

Industrial and small-scale artisanal fisheries inflict severe impacts on sea turtles (Wallace et al. 2013a). In particular, small-scale fisheries occur primarily in developing nations with limited capacity and resources to obtain data, and where fisheries management is limited or non-existent, thus hindering comprehensive evaluations of the impacts of incidental capture of marine wildlife. Weak governance, poverty, and a lack of resources for local fisheries managers means that scant attention is devoted to assessing impacts of bycatch on sea turtles. Sea turtles get captured in coastal fishing gear most commonly in gillnets, longlines and trawl nets (Wallace et al. 2013a). Industrial-scale fisheries also incidentally capture Green Turtles and other sea turtle species; conservation resolutions approved by inter-governmental regional fisheries management organizations need to be adequately observed, enforced, and monitored over time to implement intended conservation benefits.

Climate change is known to influence migratory patterns and breeding success of sea turtles (Patricio et al. 2021), and a recent study in the Great Barrier Reef, Australia—home to the world's most abundant Green Turtle subpopulation—revealed feminization and highly skewed sex ratios attributed to impacts of climate change (Jensen et al. 2018). As long-lived reptiles with temperature-dependent sex determination, all marine turtles are vulnerable to change in climate, in particular the effect of rising temperatures on offspring sex ratios and lowered hatching or reduced hatchling fitness (Patricio et al. 2021). The increased incidence of hypothermic stunning, which killed thousands of Green Turtles in Texas during the winter of 2020–2021, is suggested to be linked to range shifts of foraging Green Turtles increasing their abundance in Texas inshore waters.

Habitat loss and degradation is a continuing threat for marine turtle populations both at sea from anthropogenic activities such as fisheries and through coastal development (Biddiscombe et al. 2020). The Intergovernmental Panel on Climate Change (IPCC) predicts that as sea levels rise in the next 100 years, coastlines will migrate landwards, and increased development of anthropogenic structures will further reduce beach availability for marine turtles (Biddiscombe et al. 2020). With coastal development comes light pollution and the impacts of artificial light at night include significantly decreased survival of hatchlings and disruption of nesting females (Biddiscombe et al. 2020). Plastic pollution degrades marine turtle habitat both at sea and on land and we have yet to understand the implications of ingestion of plastics on reproduction and longevity of marine turtles (Duncan et al. 2015).

Green Turtle Fibropapilloma (GTFP) disease is prevalent in many populations worldwide, and has been shown to be more prevalent in areas with lower water quality (Van Houtan et al. 2014), typically associated with coastal development. Although GTFP does not seem to be a current major threat, disease virulence may be enhanced with predicted climate change (Patricio et al. 2021).

Threats across the different regions are varied and more detail can be found in the regional subpopulation assessments. For more details about threats to Green Turtles globally, see Seminoff et al. 2015.

Threat classification from the IUCN Red List.