Tortoises may be saved from rustlers using a highly-unusual technique - conservationists defacing their shells. By so doing, the environmental activists hope to make them unattractive to those looking to steal the animals for sale as pets. 

Worldwide, there exist around 330 species of tortoises and turtle. More than half of these are threatened with extinction.

"Numbers have been devastated through illegal collection and export to meet the international demand for the pet trade, especially in South-East Asia, where they are sold in markets particularly in Indonesia, Malaysia and Thailand," the Turtle Conservancy wrote on their Web site.

The Turtle Conservancy is managing the care of hundreds of turtles and tortoises on their grounds in the Ojai Valley in California. Among these reptiles are ploughshare tortoises from Madagascar. There are only a few hundred of these animals known worldwide, giving them the distinction of being one of the rarest animals on Earth. Their brilliant gold shell and the rarity of the specimens have combined to dramatically drive up the cost of the creature. 

Marks are etched into the shells of the animals, recording where they were born, and found. These markings are believed to be painless to the gentle creatures. These animals are often brought to lands far from their birthplace under questionable circumstances. 

A perfect ploughshare tortoise can fetch tens of thousands of dollars on the black market. Conservationists hope the etchings will ruin the re-sale value, deterring rustlers. The marks are being made both to animals at the center, as well as those remaining in the wild. Over time, the markings will wear away, so they may need to be renewed by animal workers in the future, if the program proves successful. 

"We want the hobbyist or the pet owner to think: I'm looking for a beautiful tortoise, one that's not damaged," Paul Gibbons, veterinarian with the Turtle Conservancy, told the press. 

Many of the creatures are also being fitted with radio transmitters. This way, even if poachers still take the animals, they can be located and recovered. 

The pet trade for ploughshare tortoises is particularly active in southeast Asia, where they are seen as a status symbols. Prices there can reach $50,000 or more for a first-class specimen. 

Tortoises have existed on the Earth for over 250 million years, meaning they crawled around before the first dinosaurs. The illegal trade in the animals could wipe them out in a matter of decades. The first step to save one of the most beautiful animals on Earth may just be to take away their appeal.