ABSTRACT
The short-beaked common dolphin (Delphinus delphis) is one of the most endangered Mediterranean species and stays poorly studied (Giakoumi et al., 2010). Whistles are a fundamental acoustic signal to communities of dolphins as they play an important role in social exchanges and in maintaining the cohesion within a group (King and Janik, 2015). As those vocalisations are highly variable in terms of frequency and time (Herzing, 1996), and are important for the cohesion of the group, whistle plasticity is a good indicator on how the environment, especially the ambient noise, is influencing the group. This study, conducted in the Eastern Aegean Sea, investigates on how whistle parameters of common dolphins are influenced by the immediate ambient noise within four different frequency bands where boat noise, snapping crustaceans and dolphin vocalisations can be found. Common dolphins from this region appeared to adopt an unusual response to face increased noise levels. In fact, they lower down the maximum frequency, frequency range and duration of their whistles, while they increase the peak power and frequency in response to an increased noise level within low frequency bands.
