Why are they called “green turtles”?

Japanese name: Aoumigame

English name: Green turtle

Scientific name: Chelonia mydas

In the Ogasawara Islands, the green turtle has been a long local delicacy and they are enjoyed as sashimi or stew. Green turtles got their name because of the fatty green-colored layer seen under their shells. Because they eat lots of seaweed and sea grass, this green pigment seems to be reflected in the fat. Incidentally, the name of the Loggerhead turtle comes from the fact that its appearance is reddish.

Where do they live

Green sea turtles live in different areas depending on their foraging and breeding seasons. Green sea turtles forage in a wide range of waters and many have been spotted in the waters between the southern Kii Peninsula and southern Kyushu. The breeding area is divided between the Nansei Islands and the Ogasawara Islands. Green turtles can also be seen at the Ogasawara Marine Center throughout the year. The Marine Center raises about 200 turtle hatchlings a year, mainly for headstarting (a short-term breeding and release program).

Why do they come to the Ogasawara Islands

Adult green sea turtles come to the Ogasawara Islands to mate and lay eggs. The Ogasawara Islands are the largest breeding ground for green turtles in Japan, so you can see them laying eggs on every beach during the breeding season.

Mating Season(February to May)

The male rides on the female’s back and hooks the claws of his forelimbs into the shell of the female to mate. During mating season, the male and female couples can be seen floating on the water’s surface, overlapping each other. Males are characterized by their large claws and long tails, which are larger and more developed than those of females. Their tail contains their reproductive organs (penis).

Egg Laying Season (May – August)

Green turtles come ashore to lay their eggs on the beach at night when it is quiet and still. Once ashore, the mother turtle first digs a large hole with her forelimbs, and then digs a small hole with her hind limbs to lay her eggs. The total depth of the hole is about 60 centimeters. After laying her eggs, the mother turtle carefully covers the hole again with sand using her forelimbs so that no one can see where the eggs are buried, and then returns to the sea. They don’t lay eggs only once, but four to five times every two weeks during the egg laying season, laying about 100 eggs each time. The breeding season for green turtles in Ogasawara repeats itself every two to four years.

Hatching and Emergence Period (July-October)

Forty-five to seventy days after laying eggs, hatchlings use the egg horn on the tip of their snout to break through the shell and emerge from the egg. This is called “hatching”. When all the siblings have cracked open their eggs and come out, the hatchlings all move together, moving away the sand and gradually moving upwards towards the surface. Then, about four to seven days after hatching, they all crawl out of the sand at once. This is called “emergence” and is often seen after sunset when the temperature of the sand is the lowest.

What do they eat

The diet of sea turtles differs from that of hatchlings to that of adults. In the case of green turtles, adults are herbivorous and eat different types of seaweed like “eelgrass” and “gulfweed“, tearing them up with their jagged beaks. As hatchlings, they are omnivorous and can eat things like shrimp, crabs and other crustaceans, seaweed, shellfish, fish eggs, and jellyfish. The turtles we raise at the Ogasawara Marine Center are fed fish farm feed (pellets) and vegetables.