According to Arrie Van Deventer, the orphanage's founder, dehorning the rhino and poisoning the horns have failed to deter poachers.

"Maybe this is the thing that will stop poaching", the tall, slim-built conservationist said. "This is the best idea I've ever heard".

Wildebeest, warthogs and giraffes roamed the vast conservation area as more than a dozen team members performed the delicate process on another rhino.

Larkin meticulously drilled a small hole into the horn, hammered in the radioisotope, then finished off by spraying 11,000 microdots all over the horn.

About 15,000 rhinos live in the southern African nation, according to an estimate by the international Rhino foundation.

The last phase of the project would be the animal's aftercare following "proper scientific protocol and ethical protocol", said the project's COO, a bubbly Jessica Babich.

The team would then take follow-up blood samples to ensure the rhinos were effectively protected.

The material would last five years on the horn, which was cheaper than dehorning every 18 months, Larkin said.

© Agence France-Presse