Cetaceans Change Their Acoustic Behavior During the Airgun Noise of Seismic Surveys

Seismic surveys introduce high levels of noise into the soundscape. Thus, a major concern is the effect of these noise levels on animal communication, especially for species with high hearing acuity, such as cetaceans. We evaluated the effects of airgun pulses of seismic surveys on the acoustic behavior of humpback whales (Megaptera novaeangliae) and pantropical spotted dolphins (Stenella attenuata) in the two most important basins for oil and gas off Brazil. We detect the presence of airgun pulses and measure sound pressure levels (SPL) to evaluate whether SPL changed the acoustic parameters of cetacean vocalizations. Airgun pulses increased the SPL by 17%. This changes acoustic parameters differently: whales reduced call frequency and duration, while dolphins increased these parameters. In both cases, responses may be related to physiological limitations in sound modulation of each species. This was the first report on the impacts of seismic surveys on cetaceans’ communications in Brazil and the first for the pantropical spotted dolphin on this topic in the world. Impacts vary with the frequency and duration of emissions, indicating species-specific acoustic responses that depend on airgun noise characteristics. Whales cannot make efficient adjustments at higher or lower frequencies, and dolphins cannot adjust at lower frequencies. These results are important for discussing the effects of airgun noise on cetacean communication.