Allowed to proliferate after the war, now mature adults coming home to old nesting grounds

Sea turtles returning to Ogasawaras

Kyodo

One of the Ogasawara Islands is seeing a spawning migration peak for green sea turtles born after World War II.

According to findings released Thursday by the Ogasawara Marine Center, there were 1,982 nests on Chichijima in 2013, the highest since the center started the survey in 1979.

Hunting of the green sea turtle, considered an endangered species, was discontinued during the U.S. Occupation of the Ogasawara Islands between 1946 and 1968 because most Japanese had vacated the islands. This is believed to have given the turtles the chance to increase their nesting and reproductive activities, with turtles born during those years now migrating back to the islands, the center said.

Since 1979, the center has been monitoring the turtles’ nesting activities and found that the number of nests on Chichijima grew from 119 in 1979 to 529 in 1995, then to 1,982 in 2013.

Chichijima is considered Japan’s largest breeding ground for green sea turtles. Those that nest on the island chain take up to 40 years to become reproductively mature. Although the turtles migrate long distances to find breeding sites, they are also known to return to their original nesting site to lay eggs.

The number of nests on the Ogasawara Islands, which were registered as a UNESCO World Heritage Site in 2011, started rising in the late 1980s.

Every year, the center collects some of the eggs, incubates them and releases the hatchlings into their natural habitat.

The center believes this might have been one of the reasons turtles have returned to the Ogasawaras.

Some that came ashore on Chichijima were found wandering around or stuck in ruts. They were later rescued by islanders.

“We want to make sure there are sandy beaches and a safe environment for turtles to come back to lay eggs safely,” said Koji Narushima, 34, the head of the Ogasawara Marine Center.

The turtles are sometimes rescued on Chichijima after getting stranded in dikes or straying into residential areas. The Tokyo Metropolitan Government has set up barriers along the shore in response.

The turtle, which is the largest variety of sea turtle, was designated as endangered under the Convention on International Trade in Endangered Species, known as the Washington Convention. They are found in tropical and subtropical zones.

In Japan, the turtles are seen in waters near the Ogasawara Islands, southern Kyushu and the Nansei Islands.