The booming illegal international wildlife trade forced conservationists to do the unthinkable Tuesday: Brand the golden domes of two of the rarest tortoises on Earth to reduce their black market value by making it easier for authorities to trace them if stolen.

"It's heartbreaking that it's come to this, but it's the right thing to do," Paul Gibbons, managing director of the nonprofit Turtle Conservancy's Behler Chelonian Center in Ventura County, said as he gently placed a 30-pound adult female ploughshare tortoise on a small table.

With a steady hand and an electric engraving tool, he carved an identification code on the high, rounded shell as the creature with weary eyes and gleaming carapace peered calmly into the distance. The tortoise was branded for life, which in her case would be roughly 160 years.