Ocean noise varies spatially and temporally and is driven by natural and anthropogenic processes. Increased ambient noise levels can cause signal masking and communication impairment, affecting fitness and recruitment success. However, the effects of increasing ambient noise levels on marine species, such as marine mammals that primarily rely on sound for communication, are not well understood. We investigated the effects of concurrent ambient noise levels on social whistle calls produced by bottlenose dolphins (Tursiops truncatus) in the western North Atlantic. Elevated ambient noise levels were mainly caused by ship noise. Increases in ship noise, both within and below the dolphins' call bandwidth, resulted in higher dolphin whistle frequencies and a reduction in whistle contour complexity, an acoustic feature associated with individual identification. Consequently, the noise-induced simplification of dolphin whistles may reduce the information content in these acoustic signals and decrease effective communication, parent–offspring proximity or group cohesion.

The distribution and seasonal patterns of the North Atlantic right whale, Eubalaena glacialis, inform management decisions that mitigate anthropogenic threats. Based on data from visual surveys, much of the population migrates between winter calving grounds in coastal waters adjacent to the southeast USA and summer feeding and nursery grounds adjacent to the northeast USA. However, little is known about right whale occurrence along the mid-Atlantic US migratory corridor. A better understanding of right whale occurrence in this region is needed prior to offshore wind energy development activities, which may increase mortality risks and chronic impacts on the population. We conducted an 11 mo passive acoustic survey along coastal North Carolina and Georgia near several wind energy areas to document the acoustic occurrence of right whales in the southern region of the mid-Atlantic US coast. Right whales were acoustically detected across all seasons, with peak seasonal presence occurring during autumn in the Georgia site and during winter in the North Carolina site. A secondary peak in presence also occurred during June and July in the Georgia site, when right whales were not expected to be in the area. Given the nearly year-round presence of right whales in the survey areas, these results may warrant an evaluation of current management protocols in order to provide adequate protection to the population in the face of offshore energy development activities.

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