Assessing long‐term impacts of vocal compensation to ambient noise by measuring the metabolic cost of sound production in bottlenose dolphins.

Abstract

The use of sound is essential to the survival of cetaceans. Therefore, anthropogenic sound exposure is a concern. Cetaceans can change the amplitude, duration, repetition rate, and/or frequency of sounds they produce to compensate for masking noise. Potential costs of such compensation are unknown, and no empirical data on the metabolic cost of sound production in marine mammals exist. This study aims to determine the metabolic cost of cetacean vocalizations to assess the biological significance of vocal compensation. Oxygen consumption, respiration rates, and vocalizations of two captive bottlenose dolphins were recorded during sound production at moderate levels. One dolphin produced his signature whistle while the other produced a pulsed squawk or squeaklike sound. Both types of vocalizations increased oxygen consumption while respiration rates did not change. This increased oxygen consumption is likely due to increased metabolic demand related to sound production, rather than changes in breathing patterns. Thus, acoustic signals performed in response to increased vessel presence and anthropogenic noise may increase metabolism in cetaceans. Depending on the duration and intensity of exposure, it is possible that vocal compensation responses increase total daily energy expenditure, which may impact daily prey requirements. [Study supported by the U.S. Office of Naval Research.]