Rhino keepers who successfully delivered five endangered black rhinos to Rwanda spent months hugging and coddling them inside their transport boxes to prepare them for the journey, a rhino handler told Reuters as the animals were freed on Monday.

The two male and three female eastern black rhinoceroses were flown from Safari Park Dour Kralove zoo in the Czech Republic, where they had been getting to know each other after arriving from separate European parks.

"The preparation process took several months. It started in autumn last year when two animals were brought here from Denmark and England. They started to bond, which always takes weeks because black rhinos are very alert and nervous animals," said rhino handler Jaromir Sejnoha from the Dvur Kralove Safari Park.

"In the final phase (of preparations) the rhino is trained to stay inside the box for several minutes. We feed them and hug them in there, so they aren't scared of the box and become accustomed to it, and so on the day of transportation they don't get nervous and the whole transportation goes smoothly."

There are only about 1,000 black rhinos left in the wild, Jes Gruner, the Akagera National Park manager, told Reuters. The new arrivals mean Rwanda is home to 25 of them.