Concluding Comments on Acoustic Communication
When consulting the recent history of marine mammal bioacoustics (for example, Tavolga 1964; Watkins and Wartzok 1985) one is struck by the remarkable similarity between the biological questions, experimental difficulties, scientific objectives, and technical requirements that existed in the 1960’s and those that remain today. It is not so much that there has been no effort or nothing has been accomplished in cetacean acoustics over the past thirty years. It is just that relative to other research areas, there have been few accomplishments which provide insights into cetacean acoustic communication. We have gotten better at describing the acoustic repertoires for some species and done some intelligent speculation on the functions of certain signal classes, but we still are grappling with the basic mechanics of collecting high quality field recordings, calibrating recording and analysis systems, and accurately coordinating visual observations with acoustic records.
The reasons for the slow rate of progress certainly include the difficulties of working with marine mammals in their natural environment, as well as a basic dichotomy in backgrounds for the researchers involved. Biologists and psychologists, for the most part, are not trained in physical acoustics, mathematics, or engineering; disciplines which provide advantages when dealing with issues of underwater sound transmission, reflection, absorption, and refraction. Physical acousticians and engineers, in turn, are not trained to understand how living organisms function, survive and propagate under the constraints of genetic variation and natural selection. The result is that our collective emphasis is not integrated. We need greater cross-disciplinary dialogue between the more physical sciences and the life sciences. The tools of engineering and the rigors of physical acoustics must be focused constructively on describing the details of sound production, propagation and perception in cetaceans if we are going to more understand fully their acoustic communication systems.
For example, essentially nothing has been done to describe how large whales produce sounds. Yet, we have fairly good descriptions of the sound repertoires and sound-production anatomy (including laryngeal) systems of several toothed whales and large baleen whales. Since Roger Payne and Doug Webb’s (1971) classic paper on long-range transmission of 20 Hz-fin whale sounds, no further details have emerged concerning long-range transmission of low-frequency baleen calls. Yet, we know much more about the characteristics of these biological signals and the properties of the ocean medium through which they propagate than we did 20 years ago.
We still have a great deal to learn from cetaceans regarding their solutions to underwater acoustic communication. It will take a concerted effort on the part of a spectrum of researchers to appreciate better the intricacies of cetacean sensory abilities and sound-production mechanisms. And, it will require human foresight and intelligence to modify our behaviors so that our impact on their acoustic environment is not detrimental to their continued survival.
KeywordsPhysical Acoustician Marine Mammal Sound Production Acoustic Communication Radio Telemetry
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- Tavolga, W.N. 1964. Marine Bio-Acoustics. Pergamon Press, New York. 413 pp.Google Scholar