Classification of species producing narrowband high-frequency echolocation clicks in the California Current

• Main Author: Jackson Vanfleet-Brown
• Other Authors: Ellen Hines, Anne E. Simonis, Frederick Archer
• Format: Master Thesis
• Language: English
• Published: San Francisco State University 2024
• Subjects: Phocoena phocoena
• Online Access: https://hdl.handle.net/20.500.12680/1z40m1957

Narrowband high-frequency (NBHF) clicks are signals with duration greater than 125 µs, one spectral peak above 100 kHz, and bandwidths (-3 dB) less than 10 kHz. Four species that produce NBHF clicks, and to date are not distinguished in acoustic surveys, inhabit the California Current Ecosystem (CCE): dwarf sperm whales (Kogia sima), pygmy sperm whales (Kogia breviceps), Dall's porpoises (Phocoenoides dalli), and harbor porpoises (Phocoena phocoena). From recordings of each species, validated by visual identification, we observed differences in acoustic features that suggested each species produced stereotyped calls. We used these data to build a Random Forest that correctly classified NBHF clicks with 87.7% accuracy. Defining events as collections of clicks, we also built an event classifier (BANTER) that was 85.3% correct. Using our BANTER model to then predict the NBHF species in an acoustic survey dataset showed that all species are present in the CCE but in different spatial patterns and overall proportions. This research outlines a workflow to transform data from an acoustic survey into a set of spatially and temporally defined events with associated NBHF species classification. https://doi.org/10.46569/1z40m1957