Green sea turtles are ancient, globally recognized marine species, playing an important role in marine ecosystems. These majestic reptiles are found in tropical and subtropical waters worldwide, inhabiting coastal areas of over 140 countries. Their presence contributes to the health of crucial habitats like seagrass beds. Understanding their longevity offers insights into ocean health.
Understanding Green Sea Turtle Lifespans
Green sea turtles are long-lived animals, estimated to live 70 to 90 years or more in the wild. Determining their exact age in the wild is challenging, as they lack external age indicators.
Scientists primarily estimate age through skeletochronology. This involves analyzing growth rings, similar to tree rings, found in the humerus bone of deceased turtles. These marks represent annual periods of arrested growth. Long-term tagging studies also contribute by tracking individuals over many years, providing data on growth rates and reproductive cycles. These methods provide estimations, but actual lifespans vary based on individual and environmental conditions.
The Green Sea Turtle’s Life Journey
A green sea turtle’s life begins as a hatchling, emerging from sandy beach nests. This initial phase is dangerous, as hatchlings face predators like birds and crabs during their journey to the ocean. Many do not survive this first scramble. After reaching the water, hatchlings enter a mysterious period known as the “lost years.”
During these “lost years,” young turtles live in the open ocean, often associating with floating mats of sargassum seaweed. This pelagic juvenile stage is poorly understood, as these young turtles are difficult to track in the open ocean. Juveniles eventually transition from the open ocean to coastal habitats.
Benthic juveniles and subadults adopt a primarily herbivorous diet, feeding on seagrasses and algae in shallow coastal waters. They continue to grow in these foraging grounds before reaching sexual maturity, which can occur between 25 to 35 years of age. Adult green sea turtles undertake long migrations between their coastal foraging areas and the nesting beaches where they hatched. Females return to these natal beaches every two to five years to lay clutches of approximately 110 eggs per nest.
Challenges to a Long Life
Many factors can shorten a green sea turtle’s lifespan, with human activities posing significant threats. Coastal development and construction directly impact nesting beaches, reducing available space. Degradation of foraging grounds like seagrass beds and coral reefs, due to pollution, dredging, and development, also limits food access.
Accidental capture in fishing gear, known as bycatch, is a major problem. Turtles become entangled in trawl nets, gillnets, and longlines, leading to injury, drowning, or stress. Discarded “ghost gear” also continues to entangle them. Plastic and chemical pollution also endangers these animals. Turtles may ingest plastic debris, causing internal injuries and blockages, or become entangled in derelict fishing gear.
Climate change also threatens green sea turtle survival. Rising sea levels can inundate nesting beaches. Increased sand temperatures at nesting sites can skew hatchling sex ratios towards females, impacting future breeding populations. Warmer temperatures can also decrease hatching rates or cause nest failure. Changes in ocean temperature can influence migratory patterns and food availability.
Protecting Their Future
Global conservation efforts protect green sea turtles. They are protected under national and international laws, with many populations listed as endangered or threatened. These laws prohibit killing turtles and collecting their eggs in many countries.
Habitat preservation and restoration initiatives are underway, protecting nesting beaches and enhancing foraging grounds. Communities also mitigate light pollution near nesting sites, which can disorient hatchlings. Measures to reduce fisheries bycatch include mandatory Turtle Excluder Devices (TEDs) in trawl nets, allowing turtles to escape.
Controlling marine pollution, including plastic and chemical contamination, is vital for their health. Scientific research and monitoring programs provide data to inform conservation strategies, including satellite tracking, genetic analysis, and mark-recapture studies. Raising public awareness and educating communities about threats also promotes responsible interactions. These efforts aim to ensure green sea turtles thrive and reach their natural lifespans.