Humpback whale vessel noise exposure and behavioral response on the Hawaiian breeding ground

Humpback whales (Megaptera novaeangliae) are a global species that commonly occupy coastal waters where vessel traffic is high and are thus frequently exposed to vessel engine noise. How humpback whales respond to and are affected by noise from vessels is still poorly understood. Here we quantify how often humpback whales off Maui, Hawaii, experience vessel noise and report on an experiment to examine their behavioral response. We used a combination of drone and pole tagging to attach biologging tags on 54 humpback whales in various social roles. We found that, on average, whales are exposed to vessel noise during 25% (s.d. = 17.7%) of daylight hours off Maui. In addition, by working with whales in a stationary behavioral state, and thus motionless in the water column, we conducted exposure experiments to examine the behavioral response to simulated and actual vessel noise. Movement data were quantified and compared before, during and after exposure trials. In total, playback experiments were conducted on 20 whale pods. Responses varied from subtle, temporary reactions to avoidance behavior. The results indicate that even in a location where vessel traffic is common, vessel noise can still have disruptive effects on humpback whales.