Given the scant evidence that removing the horns of rhinos reduces poaching, is it worth it?
New research shows that removing the horns of black rhinos to make them less attractive to poachers is reducing their territory sizes and making them less sociable with each other. The study, published in the journal PNAS, found that de-horned South African rhinos have home ranges that are 45 per cent smaller than those of intact animals, and that they were 37 per cent less likely to engage in social interactions.
“The big, dominant bulls that used to have very large territories that overlapped with a lot of females may now have much less territory and much less reproductive success,” says Vanessa Duthé, who led the work at Switzerland’s University of Neuchâtel.
“It’s really hard to predict the effects of this,” she says. “It doesn’t mean that population success will necessarily decline, because it might open up gaps for younger males that would not have had the space or the means before.” Indeed, a University of Bristol study published last year showed that de-horning does not negatively affect populations overall.
But such unintended behavioural consequences inevitably feed into judgements about whether this highly invasive procedure is worthwhile. Remarkably, perhaps, there is little hard evidence either way. “No one’s put all the data together to say whether it’s a really effective measure,” says Duthé.
What is clear is that the introduction of de-horning has coincided with a decline in poaching, she says. But de-horning has been accompanied by other conservation measures that may be more effective.
“It’s incredibly complicated,” says Lucy Chimes, a member of the Bristol team. “There are so many other factors involved. You have to consider what other security measures are being implemented – fencing, patrols, staff numbers – and poverty levels surrounding p
