A Swedish zoo has defended its policy of euthanising healthy young animals deemed too expensive to keep alive.

Boras Djurpark, an animal park situated 40km from Gothenberg, has killed nine healthy lion cubs since 2012. Its frank admission has sparked anger from animal rights groups in the country.

The CEO, Bo Kjellson, said some circumstances require healthy animals be put down, especially if they are rejected by their pride or cannot be rehomed elsewhere.

Just two of 13 cubs born to three separate litters have survived over the past five years. Two died of natural causes, while the remaining cubs have been put down by zoo authorities.

"I think they were killed after two years," Kjellson said in an interview with Swedish broadcaster SVT.

"At that time we had tried to sell or relocate them to other zoos for a long time but unfortunately there were no zoos that could receive them, and when the aggressions became too big in the group we had to remove some animals. And then it had to be them."

"It's no secret in any way and we do not try to hide that were working this way. So it's unfortunately a natural path for groups of lions."

Bo Kjellson
Bo Kjellson, CEO of Boras Zoo SVT

The zoo, first opened to the public in 1965, currently looks after some 600 animals from 65 different species, most of which were been born into captivity. It says it requires an expensive in-house breeding programme to maintain its population of wild animals.

Kjellson says his organisation is unsure what will happen to the zoo's remaining lion cubs in the future.

"That we will see in the future, he said. "Currently, the group works well, but some of them may become surplus animals, and then we will try to place them elsewhere.

"It could be so that we have to put them to death."

Animal studies academic Helena Pedersen has questioned whether zoos are "worth the price the animals pay for it".

"It is clear that there is a contrast to the public's perception of what a zoo is. To kill animals as part of the organisation, I think that upsets quite a few", she said to STV.