Tapanuli orangutans have been under threat from climate change fuelled storms with a single cyclone killing 7% of the monkeys in the Batang Toru forest in northern Sumatra, Indonesia
The planet’s rarest breed of great apes have been decimated by a single cyclone, new research suggests. In just four days, 7% of Tapanuli orangutans were killed.
The apes live in the Batang Toru forest in northern Sumatra, Indonesia and have been pushed to edge of extinction due to habitat destruction. In 2019, there were just 767 individual apes left, most of which live in the forest’s west block.
The study showed that “climate change-driven weather poses an immediate, catastrophic threat to the world’s rarest great ape.” Cyclone Senyar showed up on November 2025 and brought with it extreme rainfall and catastrophic landslides.
The storm killed 58 Tapanuli orangutans via drowning and suffocation under landslides. The losses count for 11% of the apes in the west block and 7% of their total numbers.
“It is extremely worrying for the future of this ape,” study co-author Serge Wich , a professor of primate biology at Liverpool John Moores University, told The Guardian .
It comes as wild monkeys in the Amazon have been discovered harbouring a lethal human illness for the first time – an alarming find that scientists believe is probably driven by civilisation encroaching further into the rainforest.
A collaborative research team from the University of Salford in the UK and Brazil’s Federal University of Amazonas discovered the hepatitis B virus in blood and liver specimens from 88 ‘new world’ primates across 28 species.
The results demonstrate evidence of human-to-monkey transmission in zones most affected by deforestation and urban expansion.
In Brazil’s Rondonia and Mato Grosso states – areas where woodland has been extensively cleared, and settlements border the forest edge – 17 of 49 monkeys tested positive for hepatitis B virus (HBV), with the genetic markers matching the strains circulating amongst local residents.
Nevertheless, in an isolated section of the upper Japurá River, deep within Amazonas state, none of the 39 monkeys sampled tested positive for infection, reports Refractor.
The difference, researchers argue, serves as a warning sign: the nearer humans venture to wildlife, the greater the likelihood we exchange diseases – with ramifications neither party is prepared for.
HBV targets the liver and can trigger cirrhosis and cancer in humans. It usually transmits through blood and certain other bodily fluids, not casual interaction, which makes the jump into wild primates even more baffling. The research, published in the journal EcoHealth, marks the first study of its kind to report HBV in New World primates, which are found in Central and South America, sparking pressing concerns about its origins and future implications.
Principal investigator Professor Jean Boubli, from the University of Salford, explained that the transmission pathway remains enigmatic.