Communication sounds for vocal exchange in belugas and Pacific white-sided dolphins

Communication sounds for vocal exchange of two odontocete species, belugas and Pacific white-sided dolphins, were studied. Belugas had a diverse sound repertoire, and their sounds were classified into five broad categories. The type of pulsed calls they exchanged had multiple broadband pulses that sounded like creaking in separation contexts. The temporal variation of the inter-pulse intervals of the creaking call differed among individuals. Pacific white-sided dolphins produced several types of pulsed calls consecutively, often exchanging them in separation contexts. A pulsed-call sequence was defined as three or more pulsed calls occurring within 325 ms, based on inter-call interval measurements. Two unrelated females shared one sequence type at one facility, whereas three females shared three sequence types and preferentially used different types at another facility. Additionally, there was a facility where related females often used the same type, and mothers increased the production rate of this type before parturition, maintaining a high rate for several hours after parturition. Various pulsed-call sequences were observed in wild dolphins migrating to Mutsu and Funka Bays in Japan. Therefore, a deep-learning-based automatic detector of pulsed calls was developed. The current challenge is to quantitatively classify the sequences observed during detection periods and elucidate their characteristics.