"In 2006, the last of China's Yangtze river dolphins--baiji--succumbed to extinction, and la vaquita marina, a diminutive porpoise endemic to the Upper Gulf of California, quietly and without fanfare inherited the title of world's most endangered marine mammal. Unlike many other critically endangered species, the vaquita is not hunted. Nor is its habitat disappearing or degraded. The species is even protected by law. Why then have its numbers plummeted...