More stubborn than white rhinos, their larger and more populous conspecifics, black rhinos are an endangered species: only 5,500 to 6,000 individuals remain, 36 percent of them in South Africa. Ms Duthé and her colleagues analyzed 15 years of data tracking the movements of 368 of these animals in 10 South African game reserves. Prior to 2013, none of the black rhinos included in the study had been dehorned, but by 2020, 63 percent had.
The researchers found that dehorning did not increase the likelihood of a rhino dying from causes other than poaching. However, the ranges of dehorned animals shrank by an average of 45.5 percent, with these numbers varying by individual. For example, one male, Hamba Njalo, lost 20 percent of his territory, leaving him just over two square miles, while another male, Xosha, lost 82 percent of his territory, leaving him just 8.5 square miles.
Also, dehorned individuals were 37 percent less likely to engage in social interactions, particularly between males.
“The study is robust and scientifically sound, with long-term data and a variety of observations,” said Sam Ferreira, a large mammal ecologist with the African Rhino Specialist Group of the International Union for Conservation of Nature, who was not involved in the research. “The results highlight important unintended consequences of trying to deal with indirect approaches such as dehorning to counter societal pressures on rhinos,” including poaching.
Rhino poaching has declined since its peak in 2015 1,349 animals were killed with a total population of African white and black rhinos of about 22,100 animals. But the situation today is still “really critical and urgent,” Ms Duthé said, as more than 548 rhinos were poached across Africa last year.
