Perth Zoo's much-loved 14-year-old African lion Mandela has died during surgery to have several fractured teeth removed, leaving staff devastated.

Senior veterinarian Simone Vitali said Mandela suddenly and unexpectedly went into respiratory and cardiac arrest.

"The vet team worked on him, went straight into emergency mode with him, but unfortunately although they got him back very briefly he eventually went into cardiac arrest and we couldn't resuscitate him," Ms Vitali said.

"There were very little signs leading up to his arrest. His anaesthetic was travelling very routinely and he had normal respiratory function and cardiac function and then both his breaths and his heart beat stopped very suddenly.

"The anaesthetic wasn't any longer than we'd normally do for an animal of his size with the problem that he had. It's something we do very routinely, so this was a very unusual event."

Second lion loss a 'real blow'

Mandela's brother Nelson died earlier this year from pneumonia and there is now only one lion left at the zoo, a female called Shinyanga.

"The loss of Mandela within the same year is a real blow for everyone ... a total shock for everybody," Ms Vitali said.

"Everybody is trying to deal with that now and go through their processes and get support from one another.

"If you ever heard a big lion roar at the zoo, it probably was Mandela, of an evening in particular.

"He was a very sociable animal, he was very interactive and he always let us know what he was feeling and what he was thinking, and he really captured the hearts of a lot of the public who saw him when they came to visit the zoo."

The zoo will conduct an autopsy on Mandela.