Auckland Zoo's decision to euthanise two elderly lions has been slammed by People for the Ethical Treatment of Animals (PETA).
Kura, 19, and her daughter Amira, 17, were put to sleep on Wednesday in what staff described as the "best call" for the animals.
The zoo said that Kura's health had deteriorated and that Amira was too closely bonded to her mother to live without her. They were Auckland Zoo's last remaining lions.
In a statement, PETA special projects coordinator Desmond Bellamy said the sad decision proved that keeping animals in captivity is cruel.
"The death of these two lions should be a wake-up call for anyone who still harbours the illusion that zoos serve any purpose beyond incarcerating intelligent animals and sentencing them to a lifetime of frustration," he said.
"Lions, like all animals - humans included - long to be free."
Mr Bellamy said even the best zoos in the world can't come close to replicating animals' natural habitats, nor are they capable of giving them the autonomy to make choices for themselves.
He said the death of Amira - who would not have been accepted by another zoo's pride after the loss of her mother - was particularly tragic.
"Had Amira been among a pride of lions where she belonged, her life would not have had to be cut short when her mother had passed away as she would have an entire community, including a family of her own, to help her overcome her grief."
Auckland Zoo currently has no lions, but has said it intends to house more big cats in the future. Mr Bellamy said that the zoo should focus on supporting the protection of animals in their native habitats instead.
"If Auckland Zoo genuinely cared about these lions the way they claim to, then they will make them the last ones to suffer in the confines of their four walls."
PETA discourages people from visiting zoos, which they have called "prisons" in the past.
"It's time we stopped treating animals as living exhibits, but rather as the sensitive individuals they are, and we can start by making the choice today never again to visit a zoo or any other institution that incarcerates animals for human amusement."