A zoo in Sweden has put down nine healthy lion cubs since 2012 because they could not afford to keep them.
Borås Djurpark resorts to the controversial practice if the animals cannot be moved to other zoos or if they are rejected by their group.
The zoo’s CEO Bo Kjellson told Swedish broadcaster SVT: “I think they were killed after two years."
“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.”
Of the thirteen cubs born in three litters at the zoo since 2012, only two have survived. Two of them died of natural causes, but the rest were put down.
Borås Zoo was founded in 1962. It looks after 600 animals of 65 different species, most of which are born in captivity, and numerous breeding programs are run to maintain its genetically-varied wildlife population.
But when the animals are no longer needed, Kjellson said it would be normal for them to be euthanized if they could not be rehomed.
He said: “It's no secret in any way and we do not try to hide that we're working this way. So it's unfortunately a natural path for groups of lions.”
Helena Pedersen, a researcher in critical animal studies, told SVT that the practice of putting down healthy animals in zoos may surprise the public.
"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 organization, I think that upsets quite a few.
"I think we need to contemplate on why it's important for us to have zoos and if it's worth the price the animals pay for it."
When asked what might happen to the remaining lion cubs at Borås Zoo, Kjellson was unsure.
He told SVT: "That we will see in the future. 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".