Their horn makes rhinos instantly recognisable.

But this animal is about to lose it.

A chainsaw cuts the growth from the sedated animal.

Conservationists in Africa have been doing this process for more than 30 years to save the endangered species from poaching.

A new study has found dehorning rhinos led to a large reduction in poaching in nearly a dozen game reserves in and around the Kruger National Park in northern South Africa.

It's an area that's home to 25% of the world's rhinos and is especially vulnerable to poaching.

“This study was actually conducted with seven years of data that were used to draw our conclusions. What that allowed, particularly in terms of dehorning, was the fact that eight different reserves dehorned, but they dehorned at different times during that seven-year period, and that gave us multiple natural experiments to see the effect of dehorning. And it consistently, no matter when it was implemented, no matter what the background conditions were, it consistently resulted in reduced poaching," says Dr Tim Kuiper, the report's lead author and a biodiversity scientist at South Africa's Nelson Mandela University.

The study found that dehorning more than 2,000 rhinos in the reserves resulted in a 78% reduction in poaching.

The conclusions seem obvious - the very thing the poachers are after is being taken away, instead of going to highly lucrative illegal markets in parts of southeast Asia and China where rhino horn products are used for traditional medicines.

The question scientists still want to investigate is the impact the invasive intervention has on rhinos.

“Poaching has a markedly bigger effect on rhino biology, behaviour, well-being, than dehorning does. So it is a trade-off. But ideally long term won't be necessary and I think we do need continued research to maybe uncover things, ways that this operation affects rhinos in ways we don't yet understand," he says.

"So far, in summary, there's no major red flags in terms of disrupting rhino biology.”

Dehorning needs to be done every 12-18 months because they grow back.

South Africa has the largest number of black and white rhinos in the world.

Namibia, Zimbabwe and Kenya also have significant populations.

There are around 17,500 white rhinos and 6,500 black rhinos left, but black rhino numbers were reduced by poaching from 70,000 in 1970 to less than 2,500 by the time poaching reached a crisis point in the mid-1990s, according to the Save the Rhino organization.

Dehorning rhinos started in southern Africa as far back as 1989. It has not been accepted without question.

There has been opposition from animal rights activists but also questions from conservationists over what impact it has on a rhino's wellbeing.

But many conservationists consider it a necessary evil, and a better option that leaving the animals vulnerable to poachers.

Rhinos use their horns to defend themselves against predators, to compete for territory and, in the case of black rhinos, to possibly help them browse for food.

“Removing their horns, what does it do, is there any social implications? Does it change their foraging habits? We don't really know," says Vanessa Duthe, a rhino researcher in South Africa not involved in the study.

"So for the social implications, we have seen that removing their horns, at least in black rhinos, cause them to change their spatial movements and to retreat into smaller home ranges.”

But she said research had found no adverse effect on rhinos' breeding rates or mortality rates because of dehorning.

Conservationists agree that dehorning alone will not end rhino poaching and Kuiper said he saw it as a short-to-mid-term solution, hoping that other efforts like more effective law enforcement and more support for game rangers on the frontline would ultimately be key.

While South Africa has been central in pulling rhinos back from the threat of extinction, more than 400 rhinos a year are still killed by poachers in the country.

The dehorning study was a collaboration between scientists from three South African universities and Oxford University in England. It also involved the South African National Park department, the World Wildlife Fund and the Rhino Recovery Fund.

The study was published Thursday in the journal Science.