A zoo in Hong Kong is investigating the death of nine monkeys, including three members of a critically endangered species, in two days.

Part of the Hong Kong Zoological and Botanical Gardens, the oldest in the territory, has been sealed off and disinfected, Hong Kong leader John Lee said in his weekly press briefing on Tuesday.

Activists said the incident raises concerns that keeping animals in captivity can increase the risk that diseases such as mpox could jump to humans.

Eight monkeys were found dead on Sunday and another died on Monday after unusual behaviour.

Experts have been called in to conduct necropsies and toxicological tests.

“Whenever we have any news, if there’s a new development, an announcement should be made as soon as possible, so that everyone can know about the facts,” Lee said.

The deceased animals included a De Brazza’s monkey, a common squirrel monkey, four white-faced sakis and three cotton-top tamarins – a species listed as critically endangered by the International Union for Conservation of Nature.

On Monday, the government held an urgent interdepartmental meeting about the deaths. It said in a statement that another De Brazza’s monkey’s behaviour and appetite were found to be unusual, requiring further observation.

However, all 80 other animals in the gardens were in normal condition, it added.

Zoonotic diseases

Animal welfare group People for the Ethical Treatment of Animals (PETA) expressed concern in a statement.

“Monkeys in captivity are often exposed to pathogens that cause diseases that can be transmitted to humans, including tuberculosis, Chagas disease, cholera and MRSA,” Jason Baker, senior vice president of PETA Asia, said.

He asserted that the only way to ensure the wellbeing of animals and prevent the spread of zoonotic diseases is to stop confining them in unnatural environments.

Built in 1860, the territory’s oldest park houses about 158 birds, 80 mammals and 21 reptiles in roughly 40 enclosures.