Canberra - The world's oldest-known Sumatran orangutan has died at a West Australian zoo at the age of 62.  

Puan, known as the "grand old lady" of Perth Zoo, was euthanised on Monday after her quality of life rapidly deteriorated due to her age.

"It's always hard to make that decision for any animal, but it was the right decision and a respectful end for an old lady who demanded respect throughout her life," Zoo's primate supervisor Holly Thompson said in a statement Tuesday.

Puan has left 11 children and 54 descendants across the United States, Europe and elsewhere, according to the zoo. Her great-grandson Nyaru was the latest individual to be released into the wild.

Puan's genetics were responsible for just under 10 per cent of the global zoological population of the species, Thompson said.

"Over the years Puan's eyelashes had greyed, her movement had slowed down and her mind had started to wander," said Martina Hart, Puan's chief zookeeper for 18 years, in an obituary published in The West Australian newspaper.

"But she remained the matriarch, the quiet, dignified lady she had always been."

Puan is believed to have been born in a jungle in Sumatra, Indonesia, in 1956 and she had been at Perth Zoo since 1968. 

She was officially recognised by Guinness World Records as the oldest of her species in 2016.

Some of Puan's descendants have even been released back into the Sumatran wild.

There are less than 15,000 of the critically endangered species, which rarely reach age 50 in the wild, left in the world, according to the World Wildlife Fund.