Acoustic Ecology of Humpback Whales (Megaptera novaeangliae) in the Hawaiian Archipelago.

Abstract

Humpback whale songs are some of the most studied of cetacean vocalizations, however some of their other non-song vocalizations are less researched. During the winter breeding season, humpback whales are a consistent source of sound in the waters surrounding Hawaii. This dissertation research focused on quantifying and describing both song and non-song vocalizations at various spatial and temporal scales. Song units from the Main and Northwestern Hawaiian Islands were identified and quantified. The pattern in song unit occurrence suggested that the songs varied geographically but there is no clear divide between the humpback songs from Main and Northwestern Hawaiian Islands, showing instead a gradient of change along the island chain. Sound levels were examined across time of day and over the course of a year for patterns of sound contribution from humpback whales around the island of Kauai. Sound levels were approximately 6 dB higher during the winter season compared to summer, when possible sound sources include humpback whales, wind, and waves. Sound levels were approximately 1 dB higher during the day compared to night during the humpback season. A calf off the coast of Maui was tagged with an Acousonde acoustic and movement recording tag. The tag recorded song from a singing escort and revealed that a calf may be exposed to sound levels from 126 to 158 dB re 1 μPa. Additional mother-calf groups were tagged in the Maui area to study the vocalizations and associated behaviors. Twelve call types were identified from tags deployed on mothers and calves, and correlated with travel and surface activity. These studies are important to understanding the way humpback whales communicate and the vocalizations are used in order to understand their use of the environment. As the levels of anthropogenic noise in the ocean increase, this knowledge is important for preserving the acoustic environment of the humpback whales.