Atomic defense: How radioisotopes are protecting Africa’s endangered rhinos

Rhinos, one of the planet’s largest and most distinctive herbivores, have existed for 55 million years .

Although they barely resemble their earliest ancestors, the Hyracodontidae , rhinos have overcome countless challenges, from ancient predators to the unforgiving cold of the Ice Age. But after enduring some of nature’s harshest threats, they now face a new and even greater danger—mankind.

With poaching and habitat loss standing as the greatest threats to all five rhino species , data suggests that around 27,000 individuals remain in the wild today. Authorities in Africa report that as of 2022, only 23,290 rhinos were left on the continent, with a total of 561 falling victim to poaching the same year. In South Africa, the struggle against illegal hunting has taken a troubling turn, with 499 rhinos lost in 2023, marking a staggering 51 percent increase from the previous year.

In an effort to combat the ongoing threat of poaching, scientists have now inserted radioisotopes into the horns of 20 live rhinos residing at The Rhino Orphanage in Mokopane, Limpopo District, South Africa.

James Larkin, PhD, a director of the University of the Witwatersrand’s Radiation and Health Physics Unit (RHPU) and leader of The Rhisotope Project , asserts that the inserted material will help disrupt the illegal rhino horn trade.

The conservation experts and veterinary professionals spent three years preparing before drilling small holes into each rhino’s horn on June 24 to insert the non-toxic radioisotopes. They will now spend six months carefully tracking the animals’ health and vital statistics to evaluate the success of the groundbreaking method.

The initiative

The project aims to utilize nuclear technology that can be detected by radiation monitors at international borders, making use of the existing global nuclear security infrastructure.

With over 11,000 radiation detection monitors at airports, harbors, and other key entry points, the system can identify even the tiniest traces of radioactive particles. Larkin believes the method offers an affordable, safe, and effective way to create long-lasting, detectable horn markers.

In an interview with Interesting Engineering (IE) , Larkin reveals that the idea surfaced in 2019 when he was approached about whether rhino horns could be made radioactive. “I replied, ‘Well, no, because I don’t want to go to jail.’ I think their intention was to insert radioactive material to poison the horns, or at least try to poison the end users,” says the scientist.

“However, because of my background in nuclear security, my understanding of nuclear security infrastructure globally, and the efforts that are going into upgrading people’s nuclear security skills, I realized there might be an opportunity to use a small amount of radioisotopes on the horns of rhinos.”

After careful consideration, Larkin determined that the right quantity would harm neither the rhino nor the environment while still achieving the goal. “But it will set off detectors at a harbor or an airport,” he continues.

When asked about the precise amount of radioisotopes that are safe for rhinos, Larkin remains tight-lipped, refusing to reveal details that could fall into the hands of poachers. “But let’s say it’s equivalent to three head CT scans a year,” the researcher says. “So yes, there is a measurable dose to the head, but it’s not at a level that is going to cause the animal any harm, and that same strength is just enough to set off the detectors.”

The process

Larkin explains that the insertion process is simple yet far more effective than dehorning a rhino. Unlike cutting off the horn, which needs to be repeated every 18 months, this procedure only requires renewal every five years.

“It’s really just a question of drilling a hole in the horn, inserting the radioisotopes, and filling the horn up,” he adds. “Obviously, you have to immobilize the rhino because a one-and-a-half-ton wild animal doesn’t exactly appreciate someone taking a drill to its horn, but the good thing in comparison to dehorning which is the only other alternative is that we use a lot less drugs.”

The scientist explains that this method greatly reduces the need for sedation, minimizes animal stress, and lowers the risks of chemical immobilization.

After the insertion, the rhinos were released into the care of a skilled team and will remain under constant 24-hour observation for six months. “Each insertion was closely monitored by expert veterinarians and extreme care was taken to prevent any harm to the animals,” says Larkin. “Over months of research and testing, we have also ensured that the inserted radioisotopes hold no health or any other risk for the animals or those who care for them.”

Further developments

Larkin highlights the project’s importance, pointing out that opportunities to save a species are rare and come along only once in a lifetime. “At the end of the six months, in December, we’ll take blood samples from the animals to check for any psychological damage, although I don’t believe there will be any,” he adds. “And from then on, we say to the world, we would love to come and help protect your animals using this technique.”

The scientist reveals opportunities to expand the project and apply the method to protect not just rhinos but other animals. “We are also looking at other animals, especially to how we might devalue elephant ivory and the potential for applying this technique to pangolins,” Larkin says.

“And just recently I had a very interesting call with people in Brazil because they are keen to see if they can use the technique to protect toucans, Amazon alligators and forest trees, as they have their own set of serious wildlife trafficking issues.”

Larkin reveals that in South Africa, a rhino falls victim to poaching every 20 hours, with their horns being trafficked globally for traditional medicines or as status symbols. “This has led to their horns currently being the most valuable false commodity in the black-market trade, with a higher value even than gold, platinum, diamonds and cocaine,” he continues. “Sadly, rhino horns play a large role in funding a wide variety of criminal activities globally.”

“Ultimately, the aim is to try to devalue rhinoceros horn in the eyes of the end users, while at the same time making the horns easier to detect as they are being smuggled across borders,” the researcher concludes.

In addition to tackling wildlife trafficking, the Rhisotope Project aims to educate and uplift local communities, with a special focus on empowering girls and women in rural areas. These women are crucial in fostering change and becoming ambassadors for rhino conservation.