A female rhinoceros died when zookeepers tried to introduce her to a potential mate for the first time.
Elena drowned while trying to escape the advances of the male white rhino named Limpopo at Wildlands Zoo in the eastern city of Emmen, near the German border.
She had become “startled” by his arrival and tried to run away.
Both animals appeared exhausted after a 15-minute chase, and Elena slipped into a shallow pool of water, landed on her side and was unable to get up, the zoo said.
Keepers tried to lure Limpopo away, but were unable to save her.
“Unfortunately, this help came too late for Elena and she had already drowned,” the zoo said in a statement.
Limpopo, 19, had arrived at the park in early September from another Dutch zoo where he sired three offspring as part of a European breeding programme.
His introduction had gone well, spending his first few weeks mixing with giraffe and zebra within two hectares of grassland.
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.
On Thursday morning, Limpopo was allowed into the area where the females were grazing.
However, the “exciting” moment they had expected went tragically wrong.
“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,” the zoo said.
“As a result, Limpopo gave chase. He seemed particularly focused on Elena, because she was the closest to him.”
The zoo said such an introduction “often requires intervention, but never before has one been fatal".
“There was no indication that this would happen,” vet Job Stumpel told local broadcaster RTV Drenthe. “The animals had met, albeit separated by a fence, and had sniffed each other.”
The team is very upset, Mr Stumpel said. “We need to process what happened. The keepers felt powerless in the presence of 2,000 kilos of muscle and horn.”
The male rhino had been moved from a German zoo six years ago because he “didn't treat the female there properly”, Dutch newspaper Brabants Dagblad 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 its perceived medicinal properties.