A sinister new twist is unfolding in South Africa’s war against rhino poaching. The practice of dehorning rhinos initially led to a drop in poaching, but as the horns begin to grow back, the poachers are returning.
“Within six months to a year after dehorning, there’s quite a bit of horn regrowth,” says statistical ecologist Res Altwegg. As little as a kilogram of horn may remain above the growth plate immediately after dehorning, he says. But black market prices are so high that even shaving off that small amount is profitable for poachers — and fatal for the rhinos.
Altwegg is a professor in the department of statistical sciences at the University of Cape Town and the founding director of the institution’s Centre for Statistics in Ecology, the Environment & Conservation, Africa’s largest statistical ecology group. His team has been working with the Greater Kruger Environmental Protection Foundation to analyse the effectiveness of anti-poaching interventions. A report on the use of statistical analysis in rhino conservation was published in Science magazine this month.
Kruger National Park rangers used to practise “strategic dehorning”, targeting rhinos considered most at risk. “It was mostly the females in certain zones of the park. And then, based on our report, they dehorned all the rhinos. And then poaching dropped there.”
While tracker dogs have helped in the capture and arrest of suspects, and digital camera technology has helped to detect poacher activity, the most effective intervention, says Altwegg, is dehorning, which involves sawing the horn off a tranquillised rhino. This intervention had such a dramatic effect in Kruger Park that it was adopted in other national parks.
A 2023 report that Altwegg and his team helped compile, “Evaluating the cost and effectiveness of rhino conservation efforts in the Greater Kruger”, points out the importance of “significant external factors such as socioeconomic inequality, entrenched criminal syndicates, corruption and horn demand”. These factors now appear to be driving poachers to target fresh horn regrowth from dehorned rhinos.
If you’re interested in watching predation, forget about Kruger. Get a microscope, a glass and a drop of water
— Res Altwegg
Apart from trying to reduce black market demand or dismantling international syndicates, Altwegg says dehorning is still the most effective deterrent. “Even though the poachers are back in Kruger, the poaching [has decreased], so it has definitely shifted the benefit-cost equation for them,” he says.
Altwegg’s team studies a range of species, including plants and microscopic organisms. Two amphibians that are found only in the Western Cape — the Table Mountain ghost frog and the Rose’s mountain toadlet — are the topics of recent PhD theses he has supervised. “There are only two Rose’s mountain toadlet populations and they are declining,” he says. “We wanted to know why and what can be done to reverse that.”
Altwegg’s statistical work as a student began with frogs in Switzerland, where he grew up and earned his first degree. He went to Norway to study house sparrows and to Canada to observe microbial protists and the worms that eat them. “If you’re interested in watching predation, forget about Kruger. Get a microscope, a glass and a drop of water. A lot is going on in there,” he says.
“My passion was always population ecology. Ultimately, we want to know why species decline and go extinct.” WWF estimates the rapid loss of species globally to be between 1,000 and 10,000 times higher than the natural extinction rate.
His South African work has included ringing bald ibis chicks off a crane at the Ingula wetland, analysing a peregrine nestling on top of the Old Mutual building in Pinelands, Cape Town, and ringing a black eagle nestling on a cliff above Hout Bay.
“A lot of people use stats to address environmental problems. We focus on the methods around statistical ecology and how we can use them for conservation,” Altwegg says. When human interactions with the environment are involved, “it becomes high-dimensional and we need a lot more data”.
Studying species interactions is also critical to conservation — especially when humans are involved.
Rather than focus on a single species, he says, “I’m usually the person who comes in and works with others who have set up experiments or long-term studies. And I’m broadly interested in global change and climate change. I’ve deliberately avoided choosing a single species.”
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