Footage showing an orangutan smoking a cigarette in Bandung Zoo in Indonesia has been shared across social media this week.
The 22-year-old Bornean orangutan Ozon picked up and started smoking a lit cigarette after a visitor flicked it inside the enclosure.
The video was captured by an anonymous contributor, who later asked Marison Guciano, of the Indonesia Animal Welfare Society, to help spread awareness of the zoo's conditions.
The Bandung Zoo had been in the spotlight recently for its poor welfare standards.
A change.org petition calling for the shutting down of the zoo collected nearly one million signatures, after neglected animals such as giraffes and elephants were reported to have starved to death.
This not the first that a zoo orangutan has been caught sneaking a smoke in Indonesia, which has an abysmal record of animal protection and one of the world's highest smoking rates.
A Bandung zoo spokesman said that while the incident was regrettable, it has staff to guard the animal enclosures.
But the officer responsible may have been in the bathroom at the time, he added.
"There's actually a sign at the location which says visitors are not allowed to give food and cigarettes to the animals," said spokesman Sulhan.
Animal activists condemned the visitor's actions but said it underlined the poor state of Indonesia's zoos.
"Weak control by zoo management also needs to be addressed," said Mr Guciano.
"But the root of the problem is that we do not have animal welfare standards at zoos. Almost all zoos are in poor condition ... from the cages and feeding needs to the animals' health."