JOHANNESBURG - Two of six critically endangered black rhinos have died of unknown causes five months after being flown from South Africa to Chad in a pioneering project to re-introduce the animals, officials said Sunday.
Rhinos in Chad were wiped out by poaching nearly 50 years ago, and the six rhinos were intended to establish a new population in the country after intensive anti-poaching measures were put in place to protect them.
"We can confirm that these two rhinos (a male and a female) were not poached," the South African environment department and Chad government said in a joint statement. "However, the exact cause of death is not yet known."
In July, there was widespread outrage after 11 black rhinos in Kenya died after having been transferred to a sanctuary, mainly due to toxic levels of salt there.
The rhinos in Chad had been roaming free in Zakouma National Park after a gradual acclimatisation process.
Their carcasses were discovered on October 15.
The surviving four rhinos are being closely monitored, the statement said.
In May, the six rhinos were sedated with darts and flown from the Addo park in South Africa to Chad, in special steel crates, accompanied by vets checking their stress levels.
The high-profile transfer was hailed as major conservation breakthrough.
There are fewer than 25,000 rhinos left in the wild in Africa due to a surge in poaching, and only 5,000 of them are black rhinos.
Black rhinos are rated as critically endangered by the International Union for Conservation of Nature.
Rhinos are targeted to feed a booming demand for rhino horn in China, Vietnam and other Asian countries, where it is believed to have medicinal qualities.
Northern white rhinos disappeared from Chad several decades ago and the last western black rhino was recorded there in 1972 after decades of poaching pushed both subspecies to local extinction.
Rhinos were re-introduced to Rwanda in 2017.