Severe rainfall in November 2025 on Indonesia’s Sumatra island killed an estimated 7% of the world’s rarest great ape species, the Tapanuli orangutan, according to a new study published in a Cell Press scientific journal.
Researchers found that about 58 Tapanuli orangutans died as a result of disasters triggered by the extreme rainfall. The species, which was only identified in 2017, is believed to number fewer than 800 individuals in total, meaning the losses represent roughly 7% of the entire population.
The study focused on the Batang Toru Ecosystem in northern Sumatra, the only known habitat of the Tapanuli orangutan. Scientists said the area was severely affected by heavy rains in November 2025, which also caused flooding and led to hundreds of human deaths in the region.
Researchers warned that increasingly frequent extreme weather events could further threaten the survival of the critically endangered species by damaging and shrinking its already limited habitat.
