High resolution acoustic recordings of wild free-ranging short-beaked common dolphins for etho-acoustical and repertoire studies

Abstract. Dolphins are highly vocal cetaceans with a complex acoustic repertoire. These marine mammals rely heavily on sound for critical activities: echolocation clicks for navigation and prey detection, whistles for social communication, and pulsed sounds for less well-documented purposes. Understanding their acoustic behaviour is essential for insights into their ecology, social structure, and responses to anthropogenic noise. However, to date, there is a lack of open-access datasets of acoustic recordings of wild free-ranging short-beaked common dolphins (Delphinus delphis), coupled with observations data. Here, we present a dataset (DOI:10.5281/zenodo.14637674, Lehnhoff (2025)) of high resolution acoustic recordings of (D. delphis) observed during various behavioural states, including foraging, travelling, socializing, milling, and attraction to the boat. The dataset was collected in the northern Bay of Biscay, France, from summers of 2020 to 2022 during surveys conducted as part of the DOLPHINFREE project. The dataset contains acoustic recordings of wild free-ranging short-beaked common dolphins (Delphinus delphis) observed during various behavioural states, including foraging, travelling, socializing, milling, and attraction to the boat. Audio recordings were performed during opportunistic encounters using two devices: a single high-quality hydrophone (sampling rate: 512 kHz, bit-depth: 32 bits) and a compact array of four hydrophones (256 kHz to 512 kHz, 16 to 24 bits) for localization purposes. The dataset comprises over 400 minutes of unedited audio recordings of D. delphis accompanied by visual observations. In total, we identified about 68,000 echolocation clicks, 4,600 whistle contours, and more that 350 pulsed sounds. This comprehensive resource is valuable for detailed studies of the acoustic repertoire of common dolphins and their two-dimensional movements.