KRUGERSDORP, South Africa – Despite the good intentions of his would-be human protectors, things wouldn't end well for Spencer the rhino.

At first, he kicked and snorted, although he had been tranquilized, and his huge prehistoric body shook violently as he lay on his side. Ten rangers struggled to hold him down.

The old bull’s eyes were covered with cloth, and ears plugged with cotton to muffle loud noises that would stress a rhino. Then the veterinarians went to work on his horns.

The experimental treatment was part of a controversial new effort to thwart rhino poaching by injecting a toxin into their horns, to dissuade people from using them in folk remedies.

Rhino poaching has become a major problem in recent years, with newly rich Vietnamese and Chinese paying exorbitant prices for horns, even though they have no medicinal value.

Dozens of journalists and wildlife experts had been invited to a safari park near Johannesburg to watch the treatment on Spencer, in hopes they’d let the world know that rhino horn was no longer safe to consume.

The treatment, conservationists said, would be harmless to the beasts.

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Charles van Niekerk, the lead veterinarian, drilled into Spencer’s horns, using a Bosch power drill and a ruler for accuracy. Into the holes he pumped an infusion of indelible pink dye and an anti-parasitic drug that is said to be toxic to humans, but not fatal. The rhino also received a microchip and a tracking device, and a DNA sample was taken.

While it is normal for the rhino to twitch after being tranquilized, van Niekerk explained, toward the end of the procedure Spencer went into convulsions.

Eventually, Spencer’s huge prehistoric-looking body went limp. He never woke up.

Autopsy results are pending, but veterinarians and other experts on hand said it was unlikely that the horn treatment killed Spencer. They suspect the rhino had an undetected heart condition and responded badly to the anesthesia. The same could happen to a rhino tranquilized to be relocated or dehorned.

“It shows how serious the crisis is, that we have to do this,” said Robi Beninca, a leader of SPOTS, a Johannesburg-based company that works to protect threatened species. “It highlights how serious it is, that we have to go and risk healthy animals.”

While South African authorities have declared rhino poaching a crime of national priority, many feel that enough isn’t being done, and they must take matters into their own hands or else the rhinos will be lost. The procedure attempted on Spencer has been successfully completed on more than 10 rhinos already, although conservationists say many more will need to be treated before it becomes a successful deterrent.

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This is just one front in the complex war against rhino poaching, with no easy solution to stop the killing.

Private game reserve owners, who profit from the tourism that rhinos and other wildlife draw, are trying tactics such as dehorning rhinos and inserting homemade poison concoctions into their horns — and then spreading the word, to try to persuade poachers to go elsewhere.

Tracking devices are widely used, and are on the verge of being small enough to be inserted into a horn and linked into a national database, like the technology used to track stolen cars.

Significant effort and money is also going into better security, by both government-run parks and private game reserves, to fight off the increasingly sophisticated poachers.

Joseph Okori, head of the World Wildlife Fund’s rhino program, attended the horn treatment event to learn about the procedure as one of the possible new ways to deter poachers.

“We must recognize that we’re dealing with a crisis on our hands,” Okori said. “The poaching crisis is not a simple issue. It’s something that needs everybody on board. We’re here to say, we must consider all deterrents that are available to the rhino community.”

Pelham Jones, a leader of the South Africa Private Rhino Owners Association, said his group won’t endorse procedures that have not been proven scientifically or that involve excessive risk to the rhino.

The association hasn’t taken a stance against dehorning, instead leaving the decision up to the individual rhino owner, but Jones said removing a rhino’s horns is not considered an economical solution.

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Dehorning also “has a lot of social behavior problems attached to it,” potentially affecting mating behavior and even causing violence between animals, he added.

To dehorn a single rhino in South Africa costs about 6,000 to 8,000 rand (about $750 to $1,000). The rhino must be tranquilized, and the process must be repeated every 12 to 18 months because the horns grow back.

In comparison, it costs about 10,000 to 15,000 rand ($1,300 to $2,000) for the horn treatment conducted on Spencer the rhino, and veterinarians said it would probably need to be repeated after four years, although this is untested.

Some rhinos have been killed by poachers even though they were dehorned.

Phila, a black rhino, was shot at least nine times in two separate attacks on a private game reserve in South Africa’s Limpopo province, even though she had been dehorned. She survived the attacks and was moved to the Johannesburg Zoo.

Poachers apparently went after the stub of horn she had left. In the dehorning process, the entire horn can’t be removed, and even a small amount has financial value.

Lorinda Hern, whose family owns the Rhino and Lion Nature Reserve where Spencer the rhino lived and died, started the rhino horn treatment project after the reserve lost a pregnant cow and a two-year-old calf to poachers in 2010.

“We effectively lost three rhinos in one incident,” she said. “We felt a desperate need to do something urgently.”

Hern doesn’t consider the treatment a permanent solution but “literally a means to buy time” until the poaching problem can be stopped.

“No deterrent is an absolute guarantee that your animal will be protected, but it’s another arrow in the quiver against possible poaching incidents,” she said.

Van Niekerk, the veterinarian who performed the rhino horn procedure at the recent media event, called the death of Spencer “a tragedy.”

“It’s a disaster,” he said, his eyes moist with tears. “There are so few of them and we have to save every one that there is.”

Van Niekerk added: “From our point of view, if we stop now then the poachers have won.