Borean languages

• They thrive in carbon-rich peat swamp forests on the Indonesian island of Borneo.
• These habitats are also the sites of massive wildfires.
• Indonesian wildfires in 2015 caused some of the worst fire-driven air pollution ever recorded.
• Frequent and persistent exposure to toxic smoke could have severe consequences for orangutans and other wildlife.

Smoke exposure poses long-term risks

• Most recently, smoke from Canadian wildfires blanketed the U.S. East Coast and Midwest in early June 2023, turning skies orange and triggering public health alerts.
• Studies have shown that human health risks from wildfire smoke include respiratory and cardiovascular illnesses, systemic inflammation and premature death.
• This made the potential implications for people and wildlife who gasped through Indonesia’s wildfire smoke for nearly two months extremely worrying.

Orangutans in the haze

• I was studying wild orangutans in the forests of Indonesian Borneo when the 2015 fires started.
• Wearing N-95 masks, we continued to monitor orangutans in hopes of learning how the animals were coping with encroaching fires and thick smoke.
• Orangutans are semi-solitary and live in dispersed communities, so these calls serve an important social role.
• We observed the orangutans for 44 days during the fires, until large blazes encroached on our study area.

Sentinel sounds

• We wanted to know whether inhaling wildfire smoke would cause vocal changes in orangutans, just as inhaling cigarette smoke does in humans.
• We were looking for acoustic clues about how this toxic air might be affecting the orangutans.
• During the fires and for several weeks after the smoke cleared, these males called less frequently than usual.

Listening to vocal species

• Increasingly frequent and prolonged exposure to toxic smoke could have severe consequences for orangutans and other animals.
• Using passive acoustic monitoring to study vocally active indicator species, like orangutans, could unlock critical insights into wildfire smoke’s effects on wildlife populations worldwide.