Study: Four Days of Extreme Rain Killed 7% of World's Rarest Orangutans
A study reveals that heavy rainfall and landslides from Cyclone Senyar in Sumatra killed 58 Tapanuli orangutans, about 7% of the critically endangered species' entire population.
Disaster in Sumatra
Cyclone Senyar, which ravaged the Indonesian island of Sumatra in late November, killed over 1,000 people and caused widespread destruction. But it also devastated one of the rarest great apes on Earth: the Tapanuli orangutan. According to a new study published Wednesday, the extreme rainfall and landslides over four days killed 58 individuals, approximately 7% of the total species population.
The researchers caution that these are conservative figures, as they do not account for rain-induced canopy damage or reduced food availability. In December, Professor Erik Meijaard of Borneo Futures had warned that the cyclone likely killed about 35 orangutans, calling it "a major blow to the population." Now, the comprehensive study shows losses nearly double that estimate.
Future Threats
The Tapanuli orangutan was only discovered in 2017, and its total population is fewer than 800. Studies indicate that if the species loses more than 1% of its population annually, it will head toward extinction. "So to have an event where about 58 individuals are killed... that's about 10 to 11% of the population there and seven percent of the whole total population of the species," said Professor Sergei Vich, a primatologist at Liverpool John Moore University. "That's way beyond what these animals can withstand."
Humanitarian workers found the carcass of what they believed to be a Tapanuli orangutan semi-buried in mud and logs in Pulo Pakkat village. "I have seen several dead bodies of humans in the past few days, but this was the first dead wildlife," said Deckey Chandra, who was working with a humanitarian team.
Climate Change Role
Scientists note that Cyclone Senyar was an anomalous event, but human-induced climate change played a significant role. They expect the frequency and intensity of extreme rainfall in the region to continue increasing, threatening the survival of Tapanuli orangutans and their habitat.
The Indonesian government has temporarily halted major developments in the Batang Toru protected forest, including mining, oil palm, and hydropower expansion. The study authors call for sustained international support, stating that "through strengthened domestic protection, climate-responsive planning, and global financial and technical assistance, we can still prevent the first modern extinction of a great ape species."
