Non-song sound production and its behavioral context in humpback whales (Megaptera novaeangliae)

Humpback whales (Megaptera novaeangliae) are famous for their sophisticated acoustic display called song, but the species also produces many sounds outside this context. Historically called "social sounds," non-song sounds may also play an important role in communication between conspecifics. This dissertation explores the production of non-song sounds from humpback whales on both a breeding and feeding ground (Hawai'i and the Northwest Atlantic, respectively). Sound emissions were measured using acoustic tags (DTAGs), and also using a towed hydrophone array. Sounds are described in detail acoustically, and behavioral context of focal individuals is investigated using body orientation and depth measurements from sensors that were integrated in the acoustic tags.;Humpback whales produced a variety of non-song sounds on both the breeding and feeding ground, most of which were higher in frequency and shorter in duration than the sounds of other baleen whale species. Sounds recorded from the feeding ground population were louder, had higher signal-to-noise ratio, and were more frequent than those from the breeding ground.;Higher sound production rates were recorded during periods when the tagged whales were approximately one body length beneath the surface. No significant variation in sound production rate was observed in relation to pitch or roll of the focal individual, or in relation to time of day, though a slight increase in sound production just after dawn and dusk on the feeding ground was evident. Further studies across wider habitat characteristics will help elucidate these trends.;Megapclicks are newly described sounds that show similarity to the click trains heard during odontocete echolocation. Megapclicks, recorded from tagged whales on a feeding ground, are paired with sharp body rolls along the sea floor that are probably feeding lunges. The description of megapclicks represents a new category of sound production for humpback whales, and for baleen whales in general.;These results enhance our understanding of this acoustically advanced species, and will also be useful in conservation and management efforts. Acoustic parameters can be used in detection algorithms, and behavioral contexts can assist in interpretation of passive acoustic monitoring research on humpback whales, and potentially other baleen whale species as well.