Although an extension of the worldwide ban on ivory exports to discourage the illegal killing of African elephants has been greeted enthusiastically in many places, the rhinoceroses (rhinos) of southern and eastern Africa are still paying with their lives for their horns, which remain prized by the Chinese for their medicinal and aphrodisiac qualities, and by the Yemenis for making dagger handles. According to a group, called Traffic, that monitors the wildlife trade throughout the world, this illegal business is on the rise. Last month, the group called for stronger international cooperation along smuggling routes and for more secure management of legal horn stocks. For its part, Zimbabwe, where there are a lot of illegal killings, has taken a very radical decision: it says it will start dehorning its rhinos. Today only five species of rhino survive in Africa and Asia. In the past, especially in the 19th and 20th centuries, they were slaughtered on a large scale by white hunters. By the 1960s, fewer than 70,000 black rhinos were left in Africa, and, over the next two decades, illegal hunters wiped out 96% of them. But since 1995, thanks to vigorous conservation efforts, the number of black rhinos has gone up again, to around 3,700. The number of white rhinos has nearly doubled over the same period, to over 14,500.