HUMPBACK WHALE SINGING BEHAVIOUR IN THE WESTERN NORTH ATLANTIC: FROM METHODS FOR ANALYSING PASSIVE ACOUSTIC MONITORING DATA TO UNDERSTANDING HUMPBACK WHALE SONG ONTOGENY

Abstract

Marine passive acoustic monitoring (PAM) is a valuable tool to assess the distribution, habitat use, and behaviour of marine mammals including the acoustically prolific humpback whale. With increasing amounts of data collected, the challenge of effectively mining PAM data for signals of interest and interpreting those signals is faced by researchers globally. I completed a literature review on the data analysis methods employed in PAM baleen whale studies (2000-2019) before exploring the dynamic and complex humpback repertoire, which is particularly challenging for PAM. The review revealed a spectrum of methodologies ranging from full manual data analysis by a human to fully automated techniques. I propose recommendations for future work to encourage the application of best practices that will result in more robust and comparable research. Humpback whale vocalizations have been studied for years, but little is known of when, where, and how seasonal male singing begins in the fall and ends in the spring. Acoustic recordings of humpback whale vocalizations from Canada, the U.S.A, and the Caribbean in 2015-2017 were manually analysed. Humpback whales were present from Labrador to Massachusetts Bay during the fall and early winter. Song development occurred gradually over weeks with vocalizations transitioning from non-song calls to song fragments to full songs. Initially sporadic in occurrence, singing began in September, but was not regularly heard until late October, when full songs were common. I found evidence that the onset of regular singing occurs earlier at lower latitudes, longer photoperiods, and higher temperatures. The theme order in early season full songs was variable, until December when theme order became more consistent with what was observed the previous spring. Dominican Republic breeding ground songs recorded in January and March were crystalized in terms of theme order. Song duration increased gradually through the breeding season. Spring song cessation was only captured at a single site/season in Canada and compared to song development, it was abrupt with few song fragments. These late season songs had consistent theme orders. I propose that the patterns observed here may in part be driven by physiological processes like those of songbirds.