Mass killings have decimated the ranks of green turtles on the offshore Taiwanese islands of Penghu, but now locals are working hard to preserve the rare species from further devastation.

There are only about 200,000 of the creatures worldwide, conservationists say, of which less than 20 females have been laying eggs on Penghu, a collection of picturesque islets about 25 miles off the western Taiwanese coast.

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Green turtles are large hard-shelled sea turtles, an endangered species protected by conservation laws in many countries. They get the name from the greenish color of their bodies, rather than the color of their shells, which varies from black to yellow to brown.

Penghu's great green turtle die-off reached its peak 20 years ago, when residents and visitors killed them in great numbers for their meat and ate the eggs of their young without regard to the future of the species.

Things began to improve in 1989 after the government in Taipei passed a conservation law banning the turtles' killing, Penghu authorities say, and six years later took another turn for the better, when the authorities set up a special nesting reserve to protect them.

Since then they have established a veterinary clinic to treat sick and injured turtles, and a nocturnal beach patrol to protect females when they lay their eggs.

Shiue Jie-yin of the Penghu County Conservation and Protection Division said the efforts have clearly prevented a recurrence of mass killings, but was unable to promise that the turtles' numbers will ever grow substantially.

"The effects of the conservation efforts can be seen only after a while," he said.

Shiue's caution is understandable.

Just last week a Taiwanese cable news station showed footage of tour operators grabbing injured green turtles trapped on the beach, and holding them out for tourists to fondle without regard for their health.

Shiue said he was surprised by the action, because most of the operators know about the conservation efforts.

"We have warned (them)," he said. "We are unwilling to see that happen again."