Illegal demand for rhino horns for use in traditional Asian medicine has soared in recent years. As a result, rhino deaths by poaching hit an all-time high in 2010, and 2011 is likely to beat that number.

Last year, the owner of the Rhino & Lion Nature Reserve near Johannesburg, South Africa, proposed a new idea to help save rhinos: poison their horns. By injecting the horns with cyanide—a process that would not harm the rhinos but could sicken or even kill anyone who tried to consume "medicine" made from the horns—Ed Hern theorized that he could disrupt the market for illegal rhino horns.

A year later, Hern and his Rhino Rescue Project have taken the idea further. They are now proposing instead to inject an anti-tick parasiticide into rhinos' horns. "The treatment is for the benefit and improved health of the animal—but it is highly toxic to humans," Hern's daughter Lorinda, who serves as the reserve's marketing manager, said last week at a press conference. Symptoms of ingesting the drug cocktail—developed by a veterinarian at Rhino & Lion Nature Reserve—include nausea, vomiting and disruptions of the nervous system.

In addition to the parasiticide, a pink dye would also be injected into the living animals' horns. Although this would not change the horns' outward appearance, the dye would show up in horns or powders passed through airport x-ray scanners, helping officials to identify the illegal materials being transported by smugglers.

The third step would involve implanting a GPS device in the horns of living rhinos (to help track horns after poachers kill an animal and before the horns are ground into powder). They also propose creating a database of rhino DNA to help link seized rhino horn to its area of origin, which could make it easier to prosecute poachers.

The Rhino Rescue Project's Facebook page discusses how last year's idea of using cyanide gave way to a less lethal alternative: "Our original idea of poisoning the horns was circumvented by the need to treat the horn, and thus the animal, against parasites instead. Furthermore, our legal advisors strongly advised against the idea of intentionally poisoning horns. Ectoparasiticides are not intended for consumption by humans, and are registered as such. Although not lethal in small quantities, [they] remain extremely toxic... Because of these side effects, the treated rhinos and their horns have to be visibly identifiable to avoid ingestion of treated horns by people. We then realized that the treatment of the horns with a mixture of ectoparasiticides coupled with an indelible dye would go a long way to helping us achieve our goal of protecting all rhinos in South Africa from poaching."

The Herns said they will make the parasiticide cocktail available to other private rhino owners.

Other groups are not so sure about the effectiveness or ethics of the treatment. "If it makes people sick, it will surely make animals sick," an Endangered Wildlife Trust spokesperson told South Africa's News24. "What if the rhinos use their horns to scratch themselves? The toxins may enter the bloodstream and have an effect. Every rhino is an individual with unique behavior. Our main concern is that this treatment is not damaging rhino or other wildlife."

Ironically, the use of poison to protect rhinos comes at a time when many poachers are poisoning rhino carcasses to hide their tracks. Dead rhinos attract flocks of vultures, which can alert rangers to recent poaching activities. Poachers are killing rhinos, chopping off the horns, and then poisoning the carcasses to kill any scavengers, including the endangered cape vulture (Gyps coprotheres). "Vultures feed in groups. So, one poisoned rhino carcass can kill at least 50 vultures at one go, Kerri Wolter of the Vulture Conservation Programme told Johannesburg's The Citizen last week. "This is frightening considering the fact that in southern Africa, we only have 2,400 pairs of breeding Cape vultures."

Photo by Johann Snyman via Flickr. Used under Creative Commons license