**Impact of Indonesian Wildfires on Bornean Orangutans: A Study on Acoustic Responses**
**Rising Incidences of Wildfires**
Wildfires have become increasingly common worldwide, leading to the release of hazardous gases and particulate matter into the atmosphere. Recently, Canadian wildfires resulted in the spread of smoke, affecting the U.S. East Coast and Midwest in June 2023. While the health risks of wildfire smoke on humans are well-documented, its impact on wildlife remains less understood. However, studies conducted at the California National Primate Research Center have indicated alarming findings. Exposure to high concentrations of particulate matter, particularly PM2.5, caused adverse effects on captive rhesus macaques, including pregnancy loss and long-term effects on various physiological parameters.
**Borneo Orangutans and Indonesian Wildfires**
Bornean orangutans, critically endangered primates, thrive in the carbon-rich peat swamp forests of Borneo, Indonesia. Unfortunately, these habitats are also prone to massive wildfires. The Indonesian wildfires in 2015, fueled by the El Niño climatic cycle, resulted in record-breaking air pollution levels. Peatland fires, characteristic of this region, produce extensive amounts of hazardous gases and particulate matter, contributing to global pollution-related deaths and illnesses.
**Implications for Orangutans and Wildlife**
Orangutans serve as an “indicator species,” reflecting the overall health of an ecosystem. Any changes in their environment tend to have noticeable effects on their health and behavior. Frequent and prolonged exposure to toxic smoke from wildfires can have severe consequences for orangutans and other wildlife. Additionally, the resulting air pollution poses significant health and safety risks for researchers studying these animals.
**Remote Sensing Techniques for Monitoring Wildlife**
Remote sensing techniques, such as satellite images, GPS data, and acoustic monitoring, have gained popularity in tracking wildlife populations and assessing their responses to environmental changes. These techniques offer valuable insights into the effects of wildfires on various species.
**Studying Bornean Orangutans and Wildfires**
In a new study, researchers focused on investigating how Bornean orangutans were affected by the toxic emissions from Indonesia’s 2015 peatland wildfires through acoustic analysis. The researchers had been studying the behavior, ecology, and acoustic communication of wild primates in Indonesia since 2005.
**Effects of Smoke Exposure on Orangutans**
The researchers observed changes in the behavior of male orangutans’ vocalizations, known as “long calls,” during the 2015 fires. These vocalizations serve social purposes, such as communicating dominance and deterring rival males. As the smoke persisted, the researchers noticed that the calls became raggedy, similar to the voices of heavy smokers.
The team monitored the orangutans for 44 days during the fires. They discovered that the orangutans reduced their activities, rested more, and traveled shorter distances. However, despite consuming more calories and being less active, the orangutans were still burning stored fat, indicating increased energy usage. The researchers speculated that inflammation caused by the smoke exposure might have been the underlying cause.
**Vocal Responses of Orangutans to Wildfire Smoke**
The researchers analyzed over 100 sound recordings of four male orangutans before and during the fires to measure their vocal responses to the smoke. Changes in vocal features, including pitch, vocal harshness, and voice shakiness, often reflect the health and condition of both humans and animals.
During the fires and for several weeks afterward, the orangutans called less frequently than usual, with their call rate halved. Their voices also dropped in pitch, exhibited more vocal harshness, and displayed irregularities. These changes in vocal quality have been correlated with inflammation, stress, and disease in humans and animals, including COVID-19.
**Implications and Monitoring Wildlife Health**
The prolonged exposure to toxic smoke can have severe consequences for orangutans and other animals. Understanding the long-term effects of peatland fires in Indonesia, one of the world’s most biodiverse countries, is crucial. By establishing connections between acoustic, behavioral, and energetic changes in orangutans, researchers can develop monitoring methods to assess wildlife health. The use of passive acoustic monitoring of vocally active indicator species, such as orangutans, could provide valuable insights into the effects of wildfire smoke on wildlife populations worldwide.