Human Auditory Discrimination of Bottlenose Dolphin Signature Whistles Masked by Noise: Investigating Perceptual Strategies for Anthropogenic Noise Pollution
Anthropogenic masking noise in the world’s oceans is known to impede many species’ ability to perceive acoustic signals, but little research has addressed how this noise pollution affects the detection of bioacoustic signals used for communication. Bottlenose dolphins (Tursiops truncatus) use signature whistles which contain identification information. Past studies have shown that human participants can be used as models for dolphin hearing, but most previous research investigated echolocation. In Experiment 1, human participants were tested on their ability to auditorily discriminate among signature whistles from three dolphins. Participants’ performance was nearly errorless (M = 98.8%). In Experiment 2, participants identified signature whistles masked by five different samples of boat noise utilizing different signal to noise ratios. Participant performance was impacted by signal to noise ratio and the similarity of the whistle and noise frequencies. Participants reported listening to the same primary auditory cue as dolphins are believed to use, frequency contour, which indicates similarities in how both species process these signals. Participants reported only a minor change in strategy between noise-present and noise-absent trials, potentially indicating that the ideal listening strategy does not change in the presence of noise, despite noise negatively impacting performance. This study may provide insight into the impacts of different types of boat noise on dolphin whistle perception. These findings can be used to generate hypotheses to test in future research with dolphin subjects, in order to create inferences of what dolphins’ strategies may be when identifying signature whistles in the presence and absence of boat noise. These findings may have implications in conservation and regulations, as they suggest that anthropogenic noise is likely to cause unique and potentially significant harm to dolphins in the marine environment
