They do, it is common practice to safely dehorn Rhino in game parks (alternatively some parks will keep all the Rhino in a smaller more easily protected area).

They do, it is common practice to safely dehorn Rhino in game parks (alternatively some parks will keep all the Rhino in a smaller more easily protected area). However, horns grow and poachers will cut off the part that cannot be safely removed and still get a good yield. I'm assuming that poachers would use tranquilizers if they could because they are less noisy and would therefore be less likely to be caught. However, they are often not very well funded and simply opportunists. Some are though.