By Alexandra Fisher
Former racehorses are being given a new lease of life on the frontline of South Africa's war on rhino poachers.
The horses are being used in riding patrols to track poachers, as fears grow that South African rhinos are on the brink of a catastrophic population decline.
With rhino poaching hitting a record level last year, many of those battling to save the animal say legalising the trade in rhino horn is the only option.
Tim Parker heads the anti-poaching unit on a wildlife reserve west of Kruger National Park.
Several times a week the horse-riding anti-poaching rangers traverse the dry expanse with a single mission - to catch the poachers.
"They offer a lot more diversity than just walking," Mr Parker said of the racehorses.
"The height advantage from tracking plays a huge factor, you can cover a lot more terrain, you can get into broken ground where vehicles can't get to.
"They're silent when you're walking, and the big factor is that you don't get tired because the horses are doing the work for you."
Champion racehorse trainer Lisa Harris brought the horses to South Africa from Zimbabwe more than a year ago to help the Rhino Revolution organisation in its fight to protect rhinos in the area.
"I saw a gap in the market here and thought we could introduce ex-racehorses that... some of them don't have other uses, for an anti-poaching campaign and it seems to be working," she said.
Since the launch of the project, no rhino has been poached on the reserve.
"We find that the poachers are very aware that they're here ... and they're a little bit scared of them," Ms Harris said.
"Racehorses have a reputation as these big fearful things and so they are quite nervous about them."
Ms Harris says one of the horses, Sonic Barrier, was born in Australia and raced in South Africa and Zimbabwe before being enlisted in the fight against poachers.
Ranger Tim Parker says his team was initially apprehensive about how the horses would adapt in a Big Five reserve.
"It was a new environment for them, so they were seeing animals that they'd never seen before. Walking in terrain that they'd never walked in before. But they settled in remarkably well," he said.
But he says poaching is difficult to stop.
"It's a multifaceted approach. It's not just us soldiers on the ground trying to combat it, because we're basically putting out fires," he said.
The number of rhinos killed last year was nearly 950 - a new national record.
South Africa's environment affairs ministry warns that if the trend continues, the wild rhino population could be wiped out within a decade.
Mr Parker says many conservationists and rhino owners now believe that legalising the horn trade is the only answer.
"One of the positive aspects is we have a renewable resource on the rhino: the horns grow back again," he said.
"You're not harming the animal at all by cutting the horn off at all. So I think if they regulate and have a legalised trade in rhino horn, I think it will certainly have a positive input into saving the species."