Localizing wild chimpanzees with passive acoustics

• Published in: Ecology and evolution 2022-05, Vol.12 (5), p.e8902-n/a
• Main Authors: Crunchant, Anne‐Sophie, Isaacs, Jason T., Piel, Alex K.
• Format: Article
• Language: English
• Subjects: Accuracy; acoustic array; Acoustics; ALS; Animals; apes; Applied Ecology; Behavior; Behavioral biology; Behavioural Ecology; Chimpanzees; Conservation; Conservation Ecology; conservation method; error; Errors; Females; Global positioning systems; GPS; Habitat utilization; Localization; Marine sciences; Microphones; Monitoring; Monkeys & apes; Playback; Population density; Population dynamics; Riparian forests; Sensors; Social behavior; Sound; Sound transmission; Spatial Ecology; Species; Terrestrial environments; Travel; Vegetation; Wildlife; Wildlife conservation; Wildlife habitats; Wind speed
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.8902

Localizing wildlife contributes in multiple ways to species conservation. Data on animal locations can reveal elements of social behavior, habitat use, population dynamics, and be useful in calculating population density. Acoustic localization systems (ALS) are a non‐invasive method widely used in the marine sciences but not well established and rarely employed for terrestrial species. We deployed an acoustic array in a mountainous environment with heterogeneous vegetation, comprised of four custom‐built GPS synchronized acoustic sensors at about 500 m intervals in Issa Valley, western Tanzania, covering an area of nearly 2 km2. Our goal was to assess the precision and error of the estimated locations by conducting playback tests, but also by comparing the estimated locations of wild chimpanzee calls with their true locations obtained in parallel during follows of individual chimpanzees. We assessed the factors influencing localization error, such as wind speed and temperature, which fluctuate during the day and are known to affect sound transmission. We localized 282 playback sounds and found that the mean localization error was 27 ± 21.8 m. Localization was less prone to error and more precise during early mornings (6:30 h) compared to other periods. We further localized 22 wild chimpanzee loud calls within 52 m of the location of a researcher closely following the calling individuals. We demonstrate that acoustic localization is a powerful tool for chimpanzee monitoring, with multiple behavioral and conservation applications. Its applicability in studying social dynamics and revealing density estimation among many others, especially but not exclusively for loud calling species, provides an efficient way of monitoring populations and informing conservation plans to mediate species loss. We deployed an acoustic array comprised of four custom‐built GPS synchronized acoustic sensors in the Issa Valley, Tanzania. We localized 282 playback sounds with a mean localization error of 27 ± 21.8 m and 22 wild chimpanzee loud calls within 52 m of the location of a researcher closely following the calling individuals. Acoustic localization is a powerful tool for species monitoring with multiple behavioral and conservation applications.