Zoo workers were left horrified after watching a lion rip out the throat of the lioness he was intended to mate with.

Nestor and Maya were supposed to mate when they were first introduced to each other as part of a Belgian theme park’s breeding program on Friday, March 15.

They had first been separated by barriers to get used to each other’s scents at the zoo in Bellewaerde, Ypres.

Both animals had been moved from Antwerp Zoo to the site in West Flanders as part of a breeding program for endangered species.

Things seemed to be okay so staff decided to remove barriers between them, according to the zoo authorities but the situation quickly deteriorated as the lions started showing signs of aggression.

“They started fighting and Nestor bit Maya in the throat,’ spokesperson Filip Van Dorpe told local media.

‘A distress signal that Nestor knows to return to his accommodation could no longer help.’

Nestor killed Maya by tearing out her neck, despite zookeepers’ attempt to save the wounded lioness.

He said:

 ‘They remain wild animals; this of course also happens in nature.

‘We deeply regret this, everyone in Bellewaerde is devastated. We went from pride to sadness in one day’.

The zookeepers at Antwerp Zoo, where Nestor was born, still have fond memories of the male lion, VRT News reported.

Ilse Segers, the zoo’s spokesperson, expressed sorrow and shock at the news Nester had killed Maya.

‘We all have reacted with complete disbelief’, she said, because he had never shown signs of aggression while at his birthplace.

‘He was a little on the shy side’, she said of the lion in his early years, ‘but since then, he has really opened up.

‘He was always gentle with his cubs and with his former partner Tasa.

You did have to leave him alone while he was eating though. He didn’t want anyone near him then’.

The breeding program is expected to continue, but it will be some time before Nestor is introduced to other lionesses, the zoo said.