Five critically endangered eastern black rhinos are ready to be transported back to their homes in Rwanda, where the species’ entire population was wiped out back in the 1990s genocide.

Three female and two male rhinos from three European countries have slowly been trained to get used to custom-made transport boxes that will take them to their home at Akagera National Park in eastern Rwanda on Sunday, according to officials from the Czech Republic’s Dvus Kralove zoo.

This will mark the biggest single transport of rhinos from Europe to Africa. The five animals, each weighing between 850 and 1,150 kilograms (1,874 and 2,535 pounds) will be tranquilized several times during the trip.

“Even though they have been well prepared, you know it is still a long trip, it is stressful, it is stressful for me, it is probably stressful for them,” said Pete Morkel, an expert on rhino relocations and internationally recognized veterinarian from Zimbabwe. “It is not easy moving black rhino, they are explosive animals, they can get unhappy very quickly. So you have to keep your finger on the pulse and see what happens and respond accordingly.”

Once they get to Rwanda, the five rhinos will have to adapt first, before they will be allowed to roam freely and join the 18 eastern black rhinos that have been transported there from South Africa two years ago.

Igor Cesar, Rwanda’s ambassador to Berlin, said it will be a “historic” transport and it will be a great recognition for his country’s efforts to restore its wildlife diversity.

Lions, rhinos and more than 500,000 people were killed in the genocide in Rwanda back in 1994. African rhinos are still poached for their horns that are being sold in illegal markets in Asian countries, most notably in Vietnam and China.

Currently, there are only a few hundred eastern black subspecies left in the world.

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