South Australia's Monarto Safari Park staff are in "mourning" following the loss of five lion cubs, who were stillborn to lioness Nia.
The open-range zoo, which is the largest safari park outside of Africa, released a statement sharing the news on Thursday afternoon.
"Keepers kept an eye on Nia via a live cam in her den and could see that, after these first two [stillborn] cubs, her labour was not progressing enough," the statement read.
"Nia's welfare during this time was our utmost priority so the decision was made to intervene around midday on Wednesday to ensure she didn't develop an infection or experience complications associated with prolonged labour.
"The vet team carried out a caesarean procedure but, despite the team's best efforts, the three cubs delivered by caesarean were unable to be revived."
The park's director, Peter Clark, said staff were "deeply saddened that these cubs didn't make it".
"Every birth at Zoos SA is a step towards saving species from extinction, these cubs were no exception," he said.
"There was nothing that could be done to save these cubs and Nia showed all instincts of being a good mum.
"This time, things just didn't work out."
Tragedy follows healthy birth of cubs in February
Monarto, located about 65 kilometres south-east of Adelaide at Monarto South, welcomed four healthy cubs born to fellow lioness Husani in February.
Mr Clark said the park often saw "the circle of life playing out".
"Husani, one of our other lionesses, only gave birth to four healthy lion cubs just a few weeks ago," he said.
"At two-and-a-half weeks old, these cubs have their eyes open and are moving around quickly as well as sleeping lots too. It will still be another week or so until they can see properly.
"During this time the cubs stay close to Mum and she only leaves for short periods to feed and be with her sisters."
Zoos SA veterinarian Jerome Kalvas said keepers and the vet team would monitor Nia to make sure she recovered comfortably.
The tragedy comes almost a year after the zoo was forced to euthanase a two-day-old zebra foal which sustained an injury that was "drastically affecting its quality of life".
