Abstract
Exposure to noise, depending on the frequency and amplitude, can cause physical damage to cetacean ears and organs as well as alter their behavior. Cetaceans have been noted to change vocal communication in response to anthropogenic noise. The whistle is one of the bottlenose dolphins’ (Tursiops truncatus) di fferent sound emissions and is thought to be the basis of the species’ acoustic communication. To date, there has been much research on the sound levels that have the potential to negatively impact the hearing of odontocetes, but less so on how sonar exposure with levels that do not induce hearing changes impact odontocete vocal behavior. Therefore, the aim of this study was to investigate bottlenose dolphin vocal communication changes during “normal” conditions with no presence of sonar noise, compared to when there is a low amplitude mid- and/or high-frequency sonar event. There was no significant difference between whistle rates during sonar events compared to control periods. Mid-frequency sonar events had a significantly higher maximum received sound level than high-frequency sonar events that had a significantly higher maximum received level than that of the controls. These results lend support to the established thresholds to ensure dolphins are able to maintain cohesion and communicate with conspecifics during lower amplitude mid- and high-frequency active sonar experiences.