A rhino died during a media demonstration of an anti-poaching treatment on Thursday, the Rhino Rescue Project said.
“He responded very well to the treatment and the procedure is 100 percent safe, but there are always huge risks when such a large animal is sedated,” said spokeswoman Lorinda Hern.
The rhino — named Spencer — died after veterinarians administered a drug to wake him up after a microchip and tracking device were implanted in his horn, said Hern.
The demonstration of the procedure was held at the Rhino and Lion Nature Reserve, in the Cradle of Humankind.
Hern, who was also Spencer’s owner, said an anaesthetic was required for the treatment.
It was suspected that Spencer had an underlying heart condition and that the anaesthetic’s antidote may have triggered heart failure.
Spencer’s age could also have played a role, as he was estimated to be 22.
Hern, who was upset at the death, said poachers created a catch-22 situation in that poaching prevention treatments required sedation, which could in some cases pose a risk to the animals.
A post mortem was being conducted to establish the exact cause of the rhino’s death.