Noise impacts on social sound production by foraging humpback whales

The Stellwagen Bank National Marine Sanctuary, located in an urbanized coastal area off the coast of Massachusetts in the United States, serves as an important foraging habitat for North Atlantic humpback whales (Megaptera novaeangliae). During the summer, large numbers of vessels are present in the vicinity of foraging humpback whales. Humpback whales produce a wide variety of low frequency(<1-kHz) social sounds. These signals are produced at lower amplitudes than song and may be subject to significant masking from noise from vessels in the area. The goal of this study was to investigate whether there were changes in the acoustic behavior of whales in the presence of ship noise. A preliminary analysis of six DTAGs (acoustic recording suction-cup tags) attached for a period of >12 hours between 2008-2012 showed decreased call rates and increased call frequency during close vessel passages. The response of the lone lactating female in the analyses was opposite of other whales, in that call rates increased during and after the increased vessel noise. This study is a first step in considering the long-term acoustic environment experienced by free-ranging humpbacks in urbanized habitats and to document the behavioral responses of individuals to shifting background noise levels.