Acoustics, balance, and chimpanzees – The ABCs of developing a deep
learning-based automated acoustic detector for wild chimpanzee (Pan
troglodytes) loud calls
Abstract
1. Passive acoustic monitoring (PAM) is a powerful tool for wildlife
monitoring, but the time and expertise required to process large volumes
of data pose significant challenges. Automated acoustic detectors
improve efficiency by speeding up data processing. Class imbalance,
resulting from fewer target signals relative to noise, complicates
development and can negatively impact performance. However, training
datasets should also reflect the conditions of real-world PAM datasets.
2. We developed an automated acoustic detector for chimpanzee loud calls
while addressing class imbalance. We predicted that greater data
diversity and high-quality data (clear signals, minimal noise
interference) would enhance network performance and that class
imbalance, by supporting diversity, is essential for functionality. We
built training datasets with data recorded in wild settings and applied
a temporal convolutional neural network approach using Deep Audio
Segmenter (DAS). We trained networks using datasets containing varying
levels of noise (50%, 75%, 90%, 99%) and also tested the
effectiveness of frequency removal in improving performance. 3. The
network performances varied significantly, with F1 scores of 0.44 to
0.86, exceeding a previous study (5% F1). The most imbalanced dataset
produced the best performing network, capturing 90% of pant-hoot events
and annotating them with 90% (SD = 20.9) accuracy. The results showed
that increased class size was associated with greater intraclass
diversity and improved precision (0.41–0.83). The networks showed
consistently high recall rates, especially when frequency removal was
not applied (0.89–0.92). 4. This study stresses the importance of class
size and diversity in developing automated acoustic detectors. It also
highlights the value of high-quality data for accurate pattern
recognition of the target signal and the importance of the noise class
for effective class decoupling and detector functionality. This research
supports the advancement of PAM in chimpanzee studies, opening new
opportunities to integrate remote sensing for efficient wildlife
monitoring.