They have done that but there is a big debate going on about that. because some people feel that without the horn the rhino cannot defend themselves, that poacher will still kill the animal since the ranger wont cut all the way and the price of the damn horn is mucho more than gold so anything they can get they will get. And there where many other things there. Some people want it to be legalized so the owners of the ranches or parks can sell the horns and the killing would stop (not really). there are alot of ideas floating around. And while somebody comes up with something the poor guys keed dropping dead.