Comparative analysis of the whistles of three oceanic dolphins in the Comoros archipelago

In my Thesis, I analysed the data collected during a series of surveys in the Shisiwani National Park (Anjouan, Comoros) from May to September 2023 with the primary objective of studying the characteristics and acoustic cues to species in the whistles of the dolphin species found in the area. Although the archipelago of the Comoros is a hotspot of cetacean biodiversity, the marine mammals that inhabit the coastal waters and lagoons surrounding the park have never been studied. Data collection was conducted from a 5m motorboat and three dolphin species were encountered: pantropical spotted dolphin (Stenella attenuata), spinner dolphin (Stenella longirostris), and melon-headed whale (Peponocephala electra). The visual inspection of spectrograms allowed the identification of 1,495 whistles with a good signal-to-noise ratio. I extracted the frequency contour of each whistle and measured several spectrotemporal features in ROCCA. Using a Random Forest, I classified the whistles according to the species, showing that these oceanic dolphins are acoustically distinguishable from each other. However pantropical spotted dolphin and spinner dolphin have a similar acoustic structure since they belong to the same genus, and they differ from the melon-headed whale acoustic structure. Moreover, within the whistles of each species, I identified whistles of stereotyped frequency modulation matching the SIGID criteria, possibly indicating the existence of signature whistles. My study provides the first characterization of the whistles of three dolphin species in the archipelago of Comoros and paves the way for developing the first fine-tuned tool for their Passive Acoustic Monitoring in these remote areas.