Elena was “startled” by the arrival of a male white rhino named Limpopo at the Wildlands zoo in the eastern city of Emmen near the German border.

After a chase the exhausted female slipped into a waterhole, at which point zookeepers lured the male away from her.

“Unfortunately, this help came too late for Elena and she had already drowned,” the zoo said.

Limpopo, 19, had arrived at the park early this month from another Dutch zoo where he sired three offspring as part of a European breeding programme.

The male and the Wildlands zoo’s two female rhinos, sisters Elena and Zahra, started getting to know each other by smelling and seeing each other in separate pens.

The “most exciting” part, the zoo said, had been planned for yesterday morning when Limpopo was allowed into the area where the females were grazing.

“From that moment on it became restless: both women were startled by the male and instead of putting him in his place together, they both ran off,” it said.

“As a result, Limpopo gave chase. He seemed particularly focused on Elena, because she was the closest to him.”

Both animals appeared exhausted after 15 minutes, and Elena slipped into a shallow pool of water, landed on her side and was unable to get up, the zoo said.

Caretakers were unable to stop her from drowning.

The zoo said such an introduction “often requires intervention, but never before has one been fatal”.

The male rhino had been moved from a German zoo six years ago because he “didn’t treat the female there properly”, the “Brabants Dagblad” newspaper said.

The southern white rhino is listed as “near threatened” by the International Union for the Conservation of Nature, with 10,080 animals in existence.

Rhinos are killed for their horns, highly prized across Asia for traditional and medicinal purposes.