Cyclone Senyar Killed Over 1,000 People and 58 Orangutans in Sumatra

Cyclone Senyar struck the Indonesian island of Sumatra in November 2025 and killed 58 Tapanuli orangutans, according to a study published this month in the journal Current Biology. The deaths equal 11% of the local population and 7% of the roughly 800 animals that remain in the wild worldwide.

The cyclone brought more than 16 inches of rain to Indonesia and produced more than 20,000 acres of landslide scars in the West Block of the Batang Toru ecosystem in North Sumatra.

Satellite data showed the slides removed nearly 12% of forest cover in that block. Researchers said the heavy rain saturated hillsides, causing sudden collapses that left orangutans little time to escape. The storm killed more than 1,000 people and displaced over one million across the region.

It also destroyed forest canopy and reduced food sources for surviving apes, effects the study did not quantify. Erik Meijaard, lead author and managing director of Borneo Futures in Brunei, said the 58 deaths may be conservative because the analysis relied on population-density estimates. “It could well be that up to 120 animals died during the landslide events,” he said.

He added that the true figure could also be lower than 58. Tapanuli orangutan females give birth every six to nine years, limiting the species’ ability to recover from sudden losses. Meijaard said annual mortality above 1% likely places the population on a path toward extinction.

Friederike Otto, a climate science professor at Imperial College London who was not involved in the study, said recovery depends on future actions. “Whether these orangutans can recover will depend on what happens next,” she told CNN. She added that another heavy rainfall event, made more likely by climate change, poses a large risk.