Details

Autor(en) / Beteiligte

• Vergés, Miriam Romagosa

Titel

Noise Exposure and Vocal Behaviour of Baleen Whales off the Azores

Ort / Verlag

ProQuest Dissertations & Theses

Erscheinungsjahr

2021

Link zum Volltext

• ProQuest

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• Fin (Balaenoptera physalus), blue (B. musculus) and sei whales (B. borealis) produce very low frequency and high amplitude vocalisations that can be regularly repeated as songs or irregularly produced as single or grouped calls. While songs are produced by males, peak during the mating season and are believed to act as reproductive displays, calls may have multiple functions associated to feeding and social contexts. By using passive acoustic techniques, that allow long-term continuous monitoring of remote areas, the study of temporal and spatial patterns of vocalisations as well as their functions can elucidate important aspects of the biology and ecology of these highly mobile and elusive species that would otherwise be difficult or impossible to obtain. The main goal of this dissertation is to investigate the vocal behaviour of fin, blue and sei whales (with a special focus on the fin whale), to contribute to a better understanding of their ecology and behaviour during migration, the least known phase of their annual life cycle. This study also investigates shipping noise levels in relation to the vocal behaviour of these three species and discusses potential implications for their migratory behaviour.Through the analysis of a large acoustic dataset collected over a period of five years in the Azores, this work studied the temporal occurrence of different vocalisations from three species of baleen whales, namely fin whale 20-Hz calls, blue whale AB and D calls and sei whale downsweeps. Fin and blue whales were acoustically present in the archipelago from autumn to spring and showed a seasonal shift in calling behaviours, from reproductive singing in winter to the production of foraging associated calls in spring. Sei whales showed a biseasonal calling pattern in spring and autumn, indicative of the migration timing of the species. Diel calling patterns showed higher diurnal fin whale singing activity, a lack of diel patterns for the two blue whale call types and increased sei whale calling during the day. Drivers of these patterns are discussed in relation to the ecology of each species and by comparing with other studies’ finding.The same dataset was used to study the function of two fin whale call types, the song forming 20-Hz call and the 40-Hz call, by examining their production in relation to season, year and zooplankton biomass, the main prey of this species. Results showed that production of 20-Hz calls was strongly influenced by season, with a clear peak during the breeding months, and secondarily by year, likely due to changes in local whale abundance. These results support the reproductive function of the 20-Hz song used as an acoustic display. Conversely, season and year had no effect on variation in 40-Hz calling rates, but prey biomass did. This is the first study linking 40-Hz call activity to prey biomass, supporting the previously suggested foodassociated function of this callThis work also investigated long-term changes in two fin whale song parameters (Internote intervals-INIs and peak frequencies) by compiling two decades of acoustic data from six different regions in the North Atlantic. First, this study documented a rapid replacement of INIs (from 19s to 12s) across a vast area of the central North Atlantic in just four winter seasons.