Green Sea Turtle | Oceana Canada

Canadian Marine Life Encyclopedia

Green Sea Turtle

Chelonia mydas

Also known as

Green turtle

Distribution

Worldwide in tropical to temperate latitudes

Écosystèmes/habitats

Sea grass beds, sandy beaches and open ocean

Feeding Habits

Herbivore

Conservation Status

Endangered

Taxonomie

Order Testudines (turtles, tortoises and terrapins), Family Cheloniidae (hard-shelled sea turtles)

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Green sea turtles have roamed the oceans for millions of years! They are ancient creatures, the largest species in the family of hard-shelled sea turtles and second largest to the leatherback turtle among all sea turtles. The adults usually live in shallow waters to feed on seagrasses and algae, and they’re the only sea turtle that is a strict herbivore. In fact, green sea turtles bite off the tops of vegetation, helping to promote healthy growth and productivity. This diet may also contribute to the greenish colour of its fat, which is where their common name comes from.

Green sea turtles are the second largest sea turtles, weighing up to 700 pounds (315 kilograms) and measuring up to 5 feet (1.5 metres) in length! However, these sizes are the maximums and are not commonly seen. Males typically have longer tails than females. Green turtles have a hard, bony shell, or carapace, that covers their body. Unlike freshwater turtles, green sea turtles cannot pull their limbs and head inside their shell for protection. They are excellent swimmers, using their large flippers to propel themselves through the water and clamber up onto land to sunbathe and nest. Green sea turtles are one of the few sea turtles known to leave the water other than at nesting times. 

Similar to other sea turtles, green sea turtles are known to travel incredibly long distances in their lifetimes. They may even cross entire oceans to travel from feeding areas to nesting beaches, as females always return to the same beach where they hatched to nest. Two of the largest remaining nesting areas are the Caribbean coast of Central America and the Great Barrier Reef in Australia.

Once at the nesting site, females will lay about 100 eggs per clutch and will nest several times over a few weeks. It takes approximately 2 months for the eggs to catch. Once the baby turtles hatch, they will make their way to the water and swim to offshore areas where they will live for several years. Interestingly, research has shown that the temperature of the sand in the nest dictates the sex of the baby turtles. 

After reaching a certain size and age, juvenile green sea turtles will journey back toward nearshore feeding grounds. Green sea turtles do not reach reproductive maturity until 25 to 30 years of age. There is still much to learn about the life cycle of green sea turtles, but it is thought that they live to 60 years or more.

While there is no directed fishery for green sea turtles in Canadian waters, interactions with commercial fishing gear poses a threat to all sea turtles in Canada. Turtles can be caught incidentally as bycatch in the pelagic longline fisheries, gillnet fisheries and, rarely, trawl fisheries along Canada’s coasts. There is high mortality of turtles caught in trawl and gillnet fisheries by drowning; however, there is higher post-release survival of turtles caught by pelagic longline since these fisheries occur closer to the surface of the water and allow the turtles to surface to breath even if they are hooked on a line. There are a few recorded interactions with green sea turtles and pelagic long-line gear on Canada’s Atlantic coast. 

Green sea turtles face many threats. One of the largest is habitat loss and coastal development of their nesting beaches. This disrupts access to nesting sites and disorients baby sea turtles trying to make their way to the ocean. Other threats that face green sea turtles include the direct killing of turtles and the harvest of their eggs, vessel strikes, bycatch or the accidental capture in fishing gear, and entanglement or ingestion of marine debris such as plastic pollution. Although many countries around the world offer green turtles some or complete legal protection, threats to their nesting beaches and direct killing of turtles for their meat and collection of eggs persist. All of these threats combined have caused green turtle populations to decrease to dangerously low levels. They are listed by the IUCN as Endangered.