Atypical rain and landslides killed 7% of the remaining Tapanuli orangutans in four days

A new study on the world's rarest great ape suggests that one brief burst of extreme weather may have wiped out a significant share of the species.

Researchers say climate-fueled extreme rains and the landslides that followed may have killed 7% of all members of the Tapanuli orangutan species in just four days, a toll they warn could carry consequences far beyond a single storm for a population of under 800 critically endangered animals.

What happened?

In the peer-reviewed journal of Current Biology, scientists estimated that 58 Tapanuli orangutans died during a November 2025 weather event in West Sumatra, where more than 39 inches of rain fell over just four days. 

As The Guardian explained, scientists combined satellite imagery with population density estimates to connect Cyclone Senyar's damage to landslides in the orangutans' primary habitat. 

The imagery indicated that about 20,000 acres of forest were destroyed, or roughly 11.7% of the key habitat area. That same landscape was already under pressure from the mining and oil palm industries.

Why does it matter?

Past research has suggested that annual population losses of about 1% of the Tapanuli orangutans could still drive the species toward extinction. Unfortunately, this single disaster exceeded that threshold several times over in less than a week.

The researchers also said fossil-fuel-driven climate change has increased the rainfall intensity by up to 50%. This means that as climate change worsens, more extreme rainfall events will occur, further endangering these animals.

What are people saying?

Study co-author and primatologist Dr. Serge Wich told The Guardian it was "tragic to lose so many apes in this way" and that the event is "extremely worrying for the future of this ape."

"The loss of an estimated 58 Tapanuli orangutans to a single climate-induced landslide event is a devastating demographic shock to the world's rarest great ape," Professor Jatna Supriatna of Universitas Indonesia said. 

Researchers behind the study also called for an immediate halt to land-use activities that continue to degrade the remaining habitat, along with broader protected areas to help stabilize the population.

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