Thirty endangered white rhinos arrived in Rwanda on Monday after travelling from South Africa in a Boeing 747, in what conservationists have said is the largest single transfer of the species ever undertaken.
Weighing up to two tonnes, the majestic animals travelled some 3,400 kilometres from South Africa's Phinda Private Game Reserve as part of a programme to replenish the species' population, decimated by poaching since the 1970s.
Once plentiful across sub-Saharan Africa, white rhino suffered first from hunting by European settlers, and later by a poaching epidemic that largely wiped them out.
The rhinos began their 40-hour journey to their new home in Akagera National Park in eastern Rwanda following months of preparation, according to charity African Parks, which is involved in the exercise.
"We had to tranquillise them to reduce their stress, which is itself risky, and monitor them," said African Parks' CEO Peter Fearnhead.
Fearnhead called the project a success after the animals were transported in a Boeing 747 and were placed in two grassy enclosures – each the size of a football stadium – after arriving in the park.
Later they will be allowed to roam the expansive park, authorities said.
"This will provide an opportunity for them to grow in a safer environment than in South Africa where three are killed per day by poachers," said the park's regional manager, Jes Gruner.
Wildlife transfers are not without risks. In 2018, four out of six relocated black rhinos died a few months after arriving in Chad.
The southern white rhino, one of two subspecies of white rhino, is now considered endangered with about 20,000 individuals remaining, according to the World Wildlife Fund (WWF).
It is classified as near-threatened by the International Union for Conservation of Nature (IUCN).
Scientists are attempting to save the northern white rhino species from extinction by harvesting eggs from the last two females left alive and using sperm from two deceased males to create embryos in an unprecedented breeding programme, which is their last chance at survival.
Rhinos have few predators in the wild due to their size but have been devastated by poaching for their horns - used in traditional Chinese medicine.