In that scenario, climate change, deforestation, intensive farming, and urban sprawl push small Bornean orangutans toward greater danger. A new threat adds to their vulnerability: wildfire smoke, both natural and human-made, which poses serious health risks to these critically endangered creatures.
These tropical peat bogs are hotspots where some of the world’s largest fires have occurred, releasing greenhouse gases, toxic smoke, and fog rich in particulates.
The health risks of wildfire smoke for humans are well known, yet the impact on wildlife living in these ecosystems has not been extensively studied.
In 2015, swamp fires in Borneo produced a dense smoke veil over the landscape. A team of scientists studied how smoke affected the long-distance vocalizations of four adult male Borneo orangutans (Pongo pygmaeus wurmbii) within a peat swamp forest. The findings appeared in iScience.
During periods of smoke, orangutans moved less and produced lower quality vocalizations, with deeper tones, reduced pitch, and more roughness and distortions, similarities to changes observed in human smokers according to researchers.
Most of these changes persisted for about two months after the smoke cleared, suggesting a lasting impact on the animals’ health.
Soil tests show that wildfires have torched forests in Borneo for millennia, but recent years have seen them grow more frequent and intense due to deforestation and peat drainage.
Smoker-like noises
When fires rage and smoke fills the air, orangutans tend to conserve energy, moving less, resting more, and burning calories at a higher rate, according to the study led by Wendy Erb of Cornell University’s Lisa Yang Center for Ornithology.
In smoky environments, orangutans emit fewer sounds, and their calls take on a smoker’s timbre. Their voices become deeper, rougher, and more tremulous. These acoustic traits align with inflammation, stress, and disease indicators observed in humans and other animals, Erb notes.
A rising frequency and intensity of forest fires in Indonesia, as elsewhere, is linked to climate change. Peat fires, however, can smolder underground for weeks, releasing exceptionally hazardous gases and fine particulates.
The researchers collaborated with the Tuanan Orangutan Research Program to collect data on adult males during the fire season, the period of highest particulate matter concentrations. Daily average particulate exposure rose nearly twelvefold above levels deemed harmful by the U.S. Environmental Protection Agency.
The orangutan is a well-established indicator species, reflecting the health of its habitat. The team concludes that increasingly frequent and prolonged exposure to toxic fumes can have severe consequences for orangutans and other wildlife, urging careful consideration of noninvasive acoustic monitoring to gauge health trends in these animals.
Dangerous particles
The findings support a pressing need to understand long-term and indirect effects of Indonesian peatland fires beyond immediate habitat loss. Linking acoustic signals, behavior, and energy use could help scientists and wildlife managers monitor the health of orangutans, a critically endangered species, through noninvasive sound monitoring.
The potential of passive acoustic monitoring lies in deepening knowledge of how wildfire smoke affects wildlife populations around the world, with implications for conservation strategies and habitat management.
Peat fires devastate forest habitats, release greenhouse gases, and generate dangerous particulates, contributing to pollution-related health risks on a global scale.
Indonesia faced its most severe combustion and smoke pollution since the 1997 El Niño droughts during 2015, when vast peatlands burned. In that year, about 12 percent of the peat area burned, a scale comparable to the size of a large European region.
Two studies published about five years ago estimate that toxic smog in 2015 led to many premature human deaths. Yet research on wildlife in these habitats remains limited. The apparent loss of around 100,000 Borneo orangutans across Kalimantan from 1999 to 2015 implies that habitat loss alone does not explain the species’ decline; toxic fumes may be a significant contributing factor to this tragedy.—As reported in iScience.—
Note: The environmental assessment references the iScience article focusing on the observed interactions among acoustic patterns, behavior, and energy use in orangutans and their potential for monitoring health through noninvasive methods.