Singing in a Crowded Ocean: Acoustic Adaptations of Great Whales and Human Impacts

Sunday, February 17, 2013
Room 310 (Hynes Convention Center)
Megan F. McKenna , National Park Service, Fort Collins, CO
Singing in a Crowded Ocean: Acoustic Adaptations of Great Whales and Human Impacts

Megan F McKenna, National Park Service- Natural Sounds and Night Skies Division

Sound plays an important role in both aquatic and terrestrial ecosystems making the acoustic environment a key habitat characteristic that has often been ignored. Animals use sound for a variety of activities, such as navigating to desirable habitat, finding food, attracting mates, avoiding predators, and establishing territory. All species of baleen whales use sound for a variety of important activities, and thus depend on the quality of the underwater acoustic environment. Technical advances in underwater acoustic recording systems, both autonomous and on-animal, facilitated not only the discovery of the diversity of whale sounds but insight on the biological function of these sounds. Examples include the complex mating display song of male humpback whales heard throughout the world’s oceans and the low frequency, long-range communication calls of blue whales that can be heard across ocean basins. The low-frequency characteristic of whale calls allows the sounds to propagate over great distances and likely serve a function in long-range communication between conspecifics for both mate attraction and social function.

Because whales use sound for a variety of activities, they depend on the quality of the underwater acoustic environment. The introduction of human-generated noise (anthropogenic noise) changes this acoustic environment, potentially disrupting or modifying these biological activities. Anthropogenic noise includes both acute, episodic sources (e.g. seismic surveys for oil exploration, military sonar) and chronic sources (e.g. ship noise) that occur almost continuously over the long term, resulting in compromised acoustic habitats throughout our world’s oceans. In some urban coastal regions that overlap with important whale habitat, the levels are increasing by 3 dB per decade or a doubling every 10 years. There is a growing body of literature documenting how whales are responding to changes in their acoustic environment and long term ecological consequences, though difficult to measure, are likely.

Mitigating underwater anthropogenic noise is challenged by the sheer scale of some of these noise sources and that marine protected area boundaries are permeable to sound and requires cross-sector and international cooperation and advances in quieter technology. National Parks, like Glacier Bay, and National Marine Sanctuaries, like Channel Islands and Stellwagen Bank, are leading the way in quantifying man-made influences on their underwater sound environments and making early efforts to understand its biological results from the perspective of baleen whale acoustic communication. Minimizing anthropogenic noise in our ocean would not only benefit whales, but myriad other species that depend on the natural underwater acoustic environment.