'Hellish In Forest': Extreme Rain Killed 58 Of The World's Rarest Tapanuli Orangutans In Indonesia

Last Updated:June 12, 2026, 05:36 IST

With fewer than 800 Tapanuli orangutans left in the wild, conservationists warn that the deaths represent a major setback for the world's rarest great ape.

A devastating cyclone that battered Indonesia’s Sumatra island last year killed at least 58 critically endangered Tapanuli orangutans, wiping out roughly 7% of the world’s remaining population and pushing the species closer to extinction, according to a new study.

The findings provide the clearest picture yet of the ecological toll of Cyclone Senyar, which unleashed four days of extreme rainfall and landslides across Sumatra in late November. Researchers said that the losses are likely conservative and do not account for longer-term impacts such as habitat destruction, canopy damage and reduced food availability.

With fewer than 800 Tapanuli orangutans left in the wild, conservationists warn that the deaths represent a major setback for the world’s rarest great ape.

How Many Orangutans Were Killed In Indonesia Storm?

Researchers estimate that 58 Tapanuli orangutans died as a direct result of the storm, almost double earlier projections made in the aftermath of the disaster. The species, first identified as distinct from other orangutans in 2017, is found only in the Batang Toru forest ecosystem of North Sumatra.

Professor Sergei Vich, a primatologist at Liverpool John Moores University and one of the study’s authors, said the scale of the losses far exceeds what the population can sustain.

“So, then to have an event where about 58 individuals are killed out of 580, that’s about 10 to 11% of the population there and seven percent of the whole total population of the species," he said, adding, “That’s way beyond these animals can withstand. So this is a huge event."

Why Is This Such A Serious Threat?

Studies suggest the Tapanuli orangutan population cannot withstand annual losses exceeding 1% without facing extinction. The deaths caused by Cyclone Senyar therefore represent a catastrophic blow to a species already considered critically endangered.

Researchers said that the impact extends beyond the animals directly killed by floods and landslides. Damage to forest habitat may reduce food availability, disrupt breeding and make long-term recovery more difficult.

“The crisis facing the Tapanuli orangutan illustrates the convergence of climate instability, biodiversity loss, and vulnerability, calling for a coordinated response matching the scale of the threat," the authors wrote.

Cyclone Senyar struck Sumatra in late November, triggering floods and landslides that killed more than 1,000 people across Southeast Asia in what became the region’s deadliest natural disaster of 2025. The storm also devastated huge swathes of forest in the Batang Toru ecosystem, home to the remaining Tapanuli orangutans.

Professor Erik Meijaard, managing director of Borneo Futures and a co-author of the study, said photographs of the animal illustrated the violence of the landslides.

“What struck me is that all the flesh had been ripped off the face," he said, adding, “If a few hectares of forest comes down in massive landslides, even powerful orangutans are helpless and just get mangled. It must have been hellish in the forest at the time."

News world 'Hellish In Forest': Extreme Rain Killed 58 Of The World's Rarest Tapanuli Orangutans In Indonesia

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