Cyclone Senyar Kills 58 of 800‑Strong Tapanuli Orangutans in Sumatra

Thu Jun 11 2026 16:02:35 GMT+0000 (Coordinated Universal Time)

Extreme rains from Cyclone Senyar wiped out 7% of the world’s rarest orangutans in just four days, a new study finds.

A devastating four‑day cyclonic storm wreaked havoc on Sumatra’s Tapanuli orangutans, killing an estimated 58 individuals—roughly 7% of the species’ precariously low population. The study warns that such extreme rainfall events can directly threaten great ape survival and that climate change is making these disasters more frequent and intense. The loss, combined with ongoing forest loss, raises serious extinction risks and calls for urgent coordinated conservation and climate‑adaptation responses.

Cyclone Senyar Killing An Estimated 58 of 800 Tapanuli Orangutans

In the darkness of late November, Cyclone Senyar unleashed four days of relentless rain that carved landslides and flooding across Sumatra, killing a predicted 58 of the critically endangered Tapanuli orangutans—about 7% of the species’ population.

“We found the carcass of a Tapanuli orangutan partly buried in mud and fallen logs in Pulo Pakkat village,” said humanitarian worker Deckey Chandra. The body showed severe damage—face tissue ripped away—confirming the extreme force of the landslides.

The study, published in Current Biology, drew on new evidence and recent field observations to highlight how an isolated storm can decimate a small, localized primate population. Researchers noted that the damage extends beyond immediate fatalities to potential canopy loss and reduced food availability, which could further diminish the species’ resilience.

Professor Erik Meijaard, author of the study and director at Borneo Futures, updated his earlier estimate from 35 to 58 deaths after reviewing additional data from affected villages.

Cyclone Senyar is considered an anomalous event, but climate scientists report it was fuelled by climate‑change‑driven warmer sea‑surface temperatures, making such extreme rainfall increasingly likely. The authors warn that the frequency and intensity of future storms could similarly devastate Tapanuli orangutans, which were only described by science in 2017.

Researchers emphasize that any loss above 1% per year could push the species toward extinction. With the Indonesian government temporarily suspending major developments in the Batang Toru protected forest—a critical habitat—there is a rare window for scientists to reassess risks and push for protective action.

“The Tapanuli crisis illustrates the convergence of climate instability, biodiversity loss and vulnerability,” the study calls, urging a coordinated response that includes climate‑responsive planning, reinforced domestic protection, and sustained international funding and technical support.

By Gavin Butler