South African project infuses rhino horns with harmless radioactive isotopes to thwart wildlife traffickers

Radioactive tracers embedded in rhino horns—even at very low activity—can be picked up by radiation portal monitors at airports and border crossings, including within fully loaded freight containers, yet pose no health risk to the animals.A South African university has launched an anti-poaching campaign to inject the horns of rhinoceroses with radioactive isotopes that it says are harmless for the animals but can be detected by customs agents.

The University of the Witwatersrand in South Africa has rolled out an anti-poaching initiative that injects harmless radioactive isotopes into rhinoceros horns, enabling customs and border security agents to detect trafficked horns using existing radiation‐detection equipment.

As part of this multi‐partner effort—uniting the University of the Witwatersrand, national nuclear energy authorities, and wildlife conservation groups—five rhinos were treated in the campaign christened Project Risotopes. These injections follow last year’s trial of roughly 20 rhinos at a sanctuary, which validated the technique ahead of Thursday’s broader launch. By tagging horns with radiolabels, even faint radioactive signals trigger alarms on standard detectors, giving authorities a powerful tool to intercept illegal shipments and pursue traffickers.

Researchers in the Witwatersrand Radiation Physics and Health Unit conducted comprehensive assessments during the pilot phase and confirmed that the isotope treatment is noninvasive and entirely safe for the rhinos.

“We have demonstrated beyond any scientific doubt that the process is completely safe for the animal and effective in making the horn detectable by international customs nuclear security systems,” said James Larkin, scientific director of the Rhisotope Project. He added that a single treated horn, carrying radioactivity far below planned operational levels, reliably set off radiation alarms. Further tests showed that these horns remain identifiable even inside 12-meter cargo containers, underscoring the method’s real-world applicability.

Once numbering around 500,000 worldwide at the beginning of the 20th century, rhino populations have plunged to about 27,000 today due to persistent black-market demand for their horns. South Africa alone hosts some 16,000 rhinos but loses roughly 500 animals each year to poachers. In response, the University of the Witwatersrand is urging private reserve owners and national conservation agencies to adopt isotope tagging across their herds, amplifying the deterrent effect and strengthening protection for this imperiled species.