Once, the black rhino was the most common species of rhino in the world, with as many as 850,000 roaming the plains of sub-Saharan Africa. But by the 1960s their numbers had dropped to around a tenth of that – the devastating result of extensive hunting and habitat destruction. Today, the rhino hovers on the brink of extinction. There are fewer than 5000 left, and despite concentrated efforts to promote population growth, the species remains critically endangered.

Earlier this month, a hunting club in Austin, Texas attracted widespread controversy by auctioning off the rights to kill one of these endangered creatures. The sale was strongly opposed by animal rights groups, and multiple protests and petitions were launched calling for its cancellation. But the sale went ahead regardless, with the winning bidder spending $350,000 on the permit – one of three issued by the government of Namibia each year, and the first to be sold outside of Africa.

Though the purchase was made anonymously, the bidder was subsequently named online as Corey Knowlton, a Texas-based big-game hunter who has since received multiple death threats in response to his provocative purchase. Yet Knowlton has defended the hunt by arguing that the killing of one rhino will benefit the species as a whole. He argues that the money raised by the auction will help fund future conservation projects, and stresses that the license requires him to work with the Namibian government to identify a rhino that is no longer able to reproduce. Their target will be an old male showing signs of aggression towards other rhinos – aggression that could, in theory, lead to younger, fertile rhinos being injured or killed.

These justifications are unlikely to convince everyone, however. Opponents maintain that sanctioning the killing of an endangered species is counterproductive, as it encourages trophy hunting and distracts from other threats such as poaching. With Knowlton still to finalise the details of his hunting trip, the debate seems set to continue for many months to come.