The Sounds of San Diego Bay May Affect Bottlenose Dolphins (Tursiops truncatus) During Cognitive Tasks

Attention is a process that guides organisms to engage in goal-directed behavior, such as seeking food when hungry. However, attention is subject to distraction, which can impact the execution of these behaviors. The ocean is full of auditory stimuli that are potentially distracting. Bottlenose dolphins (Tursiops spp.), who rely on sound as their primary sensory and communicative modality, have been shown to be impacted by noise, especially anthropogenic noise. In our study, we assessed whether louder background noise, including both natural and anthropogenic noise, was associated with worse performance on two common cognitive tasks. Using previously recorded cognitive task data, we collected information on how long it took dolphins to make a choice, how many times they considered each alternative, whether they succeeded at the trial, and the root-mean-squared amplitude of the background noise across three frequency bands while they were making a choice. In both datasets, longer choice times and more oscillations between alternatives were associated with louder noise in the highest frequency band, which mostly consists of social sounds produced by nearby dolphins. Worse performance was also associated with this higher frequency band in one of the datasets. Results were mixed for low and middle frequency bands. Our results suggest that social sounds may be more distracting than vessel noise for dolphins in San Diego Bay, though these data are correlational and should be further investigated. Future experiments should manipulate the types and magnitudes of noise that are most distracting across additional types and difficulties of cognitive tasks. This would further shed light on both welfare considerations and comparative cognition.