 Not only will the horn, which is known to be coveted for use in Chinese medicine, be unsuitable for human consumption, any poached horns will now set off detectors at border crossings, as ports and airports around the world have detectors to prevent nuclear terrorism. South Africa has the world's largest population of rhino but struggles with high poaching numbers. Almost 500 of the animals were killed for their horn last year. For NPR News, I'm Kate Bartlett in Johannesburg.