The owner of a South African game reserve is planning to inject the horns of his rhinos with poison. (Via Richard Freeman)

The owner of a South African game reserve is planning to inject the horns of his rhinos with poison.

Ed Hern, owner of the Rhino and Lion Reserve near Johannesburg, hopes the drastic measure will deter poachers who have killed more than 150 of the animals since the start of the year. Making the horns deadly to humans is the only way to halt the booming black market trade, he says.

"The aim would be to kill, or make seriously ill anyone who consumes the horn," he said. "If someone in China eats it and gets violently sick, they are not going to buy it again," Mr Hern said.

Demand from China for powdered rhino horn - erroneously believed to be an aphrodisiac - is blamed for a wave of rhino poaching across South Africa's private and public game reserves. The animals, including rare black rhino, are being slaughtered at the rate of two or three a week for their horns which can fetch up to £45,000 on the black market.

The poaching gangs are well funded, using helicopters and night vision equipment to target their prey. Mr Hern's plan to poison the horns of his herd of white rhino has caused consternation among some conservationists but, he says, the animals will not be harmed.

"We are experimenting by injecting a little of the substance every day into one of the rhino, and monitoring him carefully for any effects," he said. "It may seem outrageous, but what's really outrageous is the sight of a dead rhino with its horn sawn off," he added. That fate befell the last adult rhino in the nearby Krugersdorp reserve, whose orphaned calf was found hungry and bewildered on July 16th.

The nine-month-old, named Vuma, is now being hand reared at Ed Hern's park, along with two other calves who were also orphaned by poachers. The calves only survived the attacks because their horns were too small to interest the poachers. Small game reserves are increasingly being targeted by the criminal gangs after the Kruger park stepped up its security following a spate of rhino poaching.

So far this year, 152 animals have been killed so far this year, a significant increase on previous years.

Scientific research has proved that the keratin in rhino horns, the same substance as human hair and nails, has no medicinal value. But the myth of its properties continues to drive the trade.