Behaviour 2019
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Wildfire smoke causes vocal changes in wild Bornean orangutans
Wendy M Erb, Jessica L Lecorchick. Center for Conservation Bioacoustics, Cornell Lab of Ornithology, Cornell University, Ithaca, NY, United States

As vocal displays often convey honest information about the physical condition of the caller, changes in call acoustics may indicate fluctuations in physiology and health. While previous research has documented the effects of cigarette smoke on human speech quality, no studies have examined the impacts of wildfire smoke on nonhuman primate calls. In 2014 and 2015, widespread peatland forest fires resulted in a thick haze of wildfire smoke that covered Borneo. We studied the effects of this smoke on the long call vocalizations of Bornean orangutans. We recorded long calls of wild adult flanged males in Central Kalimantan, Indonesia, to determine the influence of smoke on orangutan long call acoustics. We used Raven Pro and WarbleR to conduct an acoustic analysis of 180 long call recordings. Using general linear mixed models, we found that long calls produced during periods of heavy smoke were significantly shorter and lower-pitched compared to long calls produced prior to the wildfires. Thus, similar to humans, orangutans’ voices are affected by exposure to smoke, though the underlying cause of these changes remains unknown.