One of Zion Wildlife Garden's original big cats, Shia, has died of what staff believes were natural causes.
Park spokeswoman Sara Reid said the 10-year-old barbary lioness died on Friday morning and autopsy results were due this week.
Ms Reid said staff at the gardens were deeply upset by Shia's death.
"This cat grew up at the park."
On Friday morning a guide was taking a tour group through the park when they found Shia unwell and lying down in the enclosure she shared with her brother Zion.
Zion had to be moved to the lock-off area before staff could enter.
By the time the staff got to Shia she was already dead.
Ms Reid said in captivity lions usually live to about 15 to 20 years.
"At 10 she would be a pretty old cat in the wild."
Shia was an important part of the Zion family, with the park named after her brother.
The siblings were hand-raised at Zion Wildlife Gardens Kerikeri before moving to Whangarei.
Ms Reid said former park owner "Lionman" Craig Busch had not been contacted about the death.
"We don't have any contact details. As far as we know he's overseas."
Staff will hold a funeral for Shia and she will be buried in the park's cemetery.
Ms Reid could not confirm rumours temporary manager Tim Husbands had left the park but said he had come in only as a consultant.