A game reserve in South Africa has taken the radical step of poisoning rhino horns so that people risk becoming "seriously ill" if they consume them.
A spokesman for the Sabi Sand reserve said a mix of parasiticides and indelible pink dye had been injected into more than 100 rhinos' horns during the past 18 months to combat international poaching syndicates.
More than 200 rhinos have been poached so far this year in South Africa, driven by demand in China and elsewhere in Asia, where horn ground into powder is used as traditional medicine.
"Consumers of the powdered horn in Asia risk becoming seriously ill from ingesting a so-called medicinal product, which is now contaminated with a non-lethal chemical package," said Andrew Parker, chief executive of the Sabi Sand Wildtuin Association, a group of landowners in Mpumalanga province.
The "toxification" process involves tranquilising a rhino, drilling a hole in its horn then injecting the dye and parasiticides, which are generally used to control ticks on animals such as horses, cattle and sheep.
"It will make people very ill, with nausea, stomach ache and diarrhoea. But it won't kill them," Parker said. "It will be very visible, so it would take a very stupid person to consume this."
Asked if he had any moral qualms about harming potentially naive consumers, Parker replied: "The practice is legal. The chemicals are available over the counter. We are advertising it and putting up signs on our fences. If somebody does consume it, they won't die and hopefully word will spread that you shouldn't take rhino horn."
The dye can be detected by airport scanners as well as when the horn is ground into a powder.
Up to 1,000 rhinos would die this year, Parker said, so bold action was necessary.
"Despite all the interventions by police, the body count has continued to climb. Everything we've tried has not been working and for poachers it has become a low-risk, high-reward ratio," he said. "By contaminating the horn, you reduce the reward and it becomes a valueless product."