Marine Life Spotlight: Sea Turtles
Regarded as the easy-going, patient, and wise, sea turtles are an emblem of longevity and stability across many of the world’s cultures. Native American folklore declares that the Great Spirit created their homeland by placing the earth on the back of a giant sea turtle. In other mythological fables, the sea turtle plays the important role of Earthdiver – being the only animal to successfully bring mud from the ocean floor to create Earth. Even in the popular Discword novels by Terry Pratchett, the world is balanced on four elephants, which in turn are standing on the back of a large turtle swimming through space, known as Great A’Tuin.
Turtles In The Wild
Our oceans are graced with seven different sea turtles: Leatherback, Green, Loggerhead, Hawksbill, Kemp’s ridley, Olive ridley, and Flatback turtles. Turtles occur from the shallow waters of the Indian Ocean, to the coral reefs of the Coral Triangle and the sandy beaches of the Eastern Pacific. Five of the seven species are found across the world’s oceans in tropical and subtropical waters, however the Kemp’s ridley is found mainly in the Gulf of Mexico, and the Flatback turtle is found mostly around northern Australia and southern Papua New Guinea. They are highly migratory that only come ashore to either bask in the sun or lay their eggs in deep pits on sandy beaches. They swim thousands of miles during their long lifetimes, and it takes decades for turtles to reproduce. Although females can lay hundreds of eggs during the nesting season, not many of the small hatchlings will survive their first year of life. The hatchlings are prey for seabirds, crabs, and mammals before they even reach the ocean, and once in the water, they become prey for larger fish species.
Each of the seven turtle species relies on a different diet: Greens eat seagrass, Leatherbacks feed mostly on jellyfish and soft-bodied animals; Loggerheads eat heavy-shelled animals such as crabs and clams; Hawksbills depend on sponges and invertebrates; and Kemp’s ridley prefers crabs. In this manner, different turtle species crossing paths do not pose threats to the survival of the other.
Sea turtles not only matter in fiction and mythology – they are a fundamental link in marine ecosystems. Due to their grazing activities, they help maintain the help of seagrass beds and coral reefs. This benefits commercially important marine species, such as shrimp, lobster and tuna.
Threats To Turtles
Over the past 200 years, all species have been impacted by human activities, leading to sea turtle species being classified as endangered on the IUCN Red Data List. Humans historically captured and killed turtles for their eggs, meat, skin and shells, and today turtles are still suffering from poaching and over-exploitation. Turtles are also killed for traditional medicine and religious ceremonies. Despite international trade in turtles being prohibited under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), illegal trafficking persists.
The nesting sites of turtles are under threat due to construction and tourism activities on beaches. Uncontrolled coastal development and vehicle access to beaches have significantly disturbed and destroyed sea turtle nesting beaches. Lights from roads adjacent to beaches disorient new hatchlings, causing them to move away from the sea, and vehicle traffic on the beach compresses the sand, making it impossible for female turtles to dig nests.
Turtles’ feeding grounds, such as the shallow seagrass beds and coral reefs, are also being destroyed due to human activities. Sedimentation and chemical run-off from onshore fertilizers are impacting the feeding grounds of turtles.
Turtles are prone to accidental capture during fishing activities – known as bycatch. Turtles are either swooped up in the nets of trawling vessels, or get caught on the hooks of long-liner fishing vessels. Hundreds of thousands of sea turtles are accidentally caught and killed this way each year. Once captured in a net, the sea turtle is unable to go to the surface to breathe, and as a result, the turtles drown. Loggerheads, Greens and Leatherbacks are particularly prone to being victims of bycatch.
Climate change is posing the largest risk to turtles, as it alters the sand temperatures at nesting sites, which in turn affects the sex of the turtle hatchlings, with fewer males hatching. Warmer ocean temperatures also lead to loss of feeding grounds, and an increase in frequency and severity of storms are destroying beaches and damaging nests.
Sea turtles feed on jellyfish, and pollution is impacting this natural behavior. Sea turtles mistake floating plastic – such as shopping bags – for jellyfish, and choke when they try to eat them. Lost or discarded fishing gear – called ghost gear – can also entangle turtles, leaving the turtle unable to swim or feed. Trash washed up on beaches trap hatchlings and prevent them from reaching the ocean, and oil spills affect, and poison, sea turtles of all ages.
Sea Turtle Conservation
Conservation organizations are working around the clock to eliminate sea turtle bycatch from fishing activities, reduce the unsustainable harvest and illegal trade in sea turtles, and protect critical sea turtle habitats. This includes establishing and managing protected areas around nesting beaches, raising awareness with governments and local communities, promoting sustainable ecotourism, and lobbying for turtle-friendly fishing practices.
Because local exploitation and sale of turtle meat and eggs is driven by a lack of economic choices offered to local communities, conservation organizations are assisting to develop alternative livelihoods so that people are not required to be dependent on the sale of turtle products. Residents from coastal communities are trained to act as rangers that patrol turtle nesting beaches, and protect against egg poaching.
Turtle-friendly fishing practices are possible. For long-line fishing vessels, turtle-friendly (“circle”) hooks can be used, and turtle exclusion devices can be used in nets. Lights can also be used to reduce turtle bycatch by 60 – 70%.
Satellite Tracking Turtles
The use of satellite tags on turtles allows researchers to track sea turtles during their migration. The tags are designed to fall off eventually, and provide scientists with important information regarding feeding areas, to anticipate where turtles may come in contact with the fishing industry.
Although the threats faced by sea turtles seem almost too big to overcome, greater public awareness and support for sea turtle conservation initiatives is the first priority. It is everyone’s responsibility to understand and improve the conservation of the world’s sea turtles.