CNN.com has an interesting article and video  up about a new GPS tracking system that conservation officials are using in South Africa to stop rhino poaching.
They burrowed an eight centimeter hole [in the rhino's horn], about an inch wide. Inside they embedded a silver canister and then plugged up the incision with putty and wrapped some masking tape over the rhino horn, like a make-shift bush bandage. This radical surgery is an experiment that many in South Africa hope will help to curtail the massive surge in rhino poaching. More than 250 rhinos have been slaughtered for their horns this year, a huge increase compared to previous years.