Green sea turtles are large marine reptiles found in tropical and subtropical oceans. They are herbivores, primarily consuming seagrasses and algae, which distinguishes them from other sea turtle species. They spend most of their lives underwater, prompting questions about their longevity.
Green Sea Turtle Lifespan
Green sea turtles are known for their long lifespans, with estimates suggesting they can live for 70 years or more in the wild, with some indications pointing to potential lifespans reaching 90 or 100 years. Determining their exact age is challenging, but scientists use tagging, skeletochronology, and genetic analysis.
Their longevity is partly attributed to physiological characteristics. Green sea turtles possess a slow metabolism, which allows them to conserve energy efficiently and potentially reduces cellular damage. Their slow growth rate and considerable size as the largest hard-shelled sea turtles also contribute to their resilience in marine ecosystems.
Life Stages and Development
Their life cycle involves several distinct stages. Adult females typically migrate every two to five years to nest, often returning to their hatching area. During a nesting season, a female may lay around 110 eggs per nest in multiple clutches.
Hatchlings embark on a journey to offshore pelagic habitats, spending their initial “lost years” in the open ocean. This oceanic phase can last for several years before they transition to coastal environments. Juveniles then move to shallower foraging grounds, continuing growth and development.
Green sea turtles reach sexual maturity between 25 and 35 years of age, though this can range from 20 to 50 years. After reaching maturity, they undertake reproductive migrations, contributing to future generations.
Influences on Longevity
Green sea turtles face a variety of factors that can influence their lifespan, ranging from natural challenges to significant human-related impacts. In early life, eggs and hatchlings are vulnerable to natural predators such as raccoons, foxes, birds, ghost crabs, fish, and sharks. Over 90% of hatchlings may be consumed by predators during their journey from nest to sea. Adult turtles have fewer natural predators, primarily large sharks, killer whales, and occasionally crocodiles or jaguars when on land.
Diseases also pose a threat, notably fibropapillomatosis (FP). This disease causes external and internal tumors that can impair a turtle’s ability to swim, feed, and see, sometimes leading to death. FP is most prevalent in green turtles, associated with a herpesvirus, and linked to degraded marine habitats. Habitat degradation, including the loss of nesting beaches and foraging grounds, directly affects their survival. Climate change, leading to sea level rise and warming temperatures, further impacts nesting success and can even affect hatchling sex ratios.
Human activities present widespread threats that can shorten a green sea turtle’s life. Accidental capture in fishing gear (bycatch) is a common cause of mortality, involving equipment like trawl nets, gillnets, and longlines. Plastic pollution is another danger, as turtles often mistake plastic debris for food, leading to ingestion that can cause internal blockages, organ damage, starvation, or buoyancy issues. Over half of all sea turtles may have ingested plastic.
Vessel strikes, or collisions with boats, are problematic because turtles spend time at the surface to breathe or bask and have limited hearing and vision, making them vulnerable in high-traffic areas. In Florida, 20-30% of stranded sea turtles show injuries consistent with vessel strikes. Additionally, illegal harvesting of turtles for their meat, eggs, and shells continues in some regions.
Protecting Their Future
Extensive conservation efforts and legal protections are in place to help ensure their survival and ability to live longer lives. In the United States, the green sea turtle is listed under the Endangered Species Act (ESA), with distinct population segments classified as either threatened or endangered. International agreements, such as the Convention on International Trade in Endangered Species (CITES), list green turtles in Appendix I, prohibiting international trade. The Inter-American Convention for the Protection and Conservation of Sea Turtles (IAC) provides a framework for countries in the Americas and Caribbean to protect these migratory species.
Marine Protected Areas (MPAs) play a significant role in safeguarding green sea turtles. These designated areas restrict human activities to protect vital habitats, including foraging grounds and nesting sites. Over one-third of the world’s green turtles are found within MPAs, highlighting their importance as safe havens.
Research and monitoring programs, often involving tagging with flipper, passive integrated transponder (PIT), or satellite tags, help scientists track turtle movements, migrations, and nesting patterns. This data is crucial for understanding their behavior and identifying areas in need of protection. Public awareness campaigns and community involvement also contribute to conservation by promoting responsible boating practices, encouraging the use of turtle excluder devices (TEDs) in fishing gear, and advocating for reduced plastic consumption. These collective actions aim to mitigate threats and allow green sea turtles to thrive.