Analisi acustica di Megaptera novaeangliae nel sud dell'Islanda

The abundance and migratory routes of humpback whales (Megaptera novaeangliae) in the north and west of Iceland have been well documented over the years thanks to research institutions and whale-watching companies. There is an opposite scenario in the south of Iceland, where no studies have focused specifically on the presence of humpback whales in the past. As a result, even though the species has been opportunistically observed in both summer and winter, no research was conducted on the seasonality or frequency of their occurrence in the south of Iceland. This project aimed at providing the first acoustic analysis of humpback whales in the south of Iceland. Acoustic monitoring, using an autonomous moored hydrophone, was carried out from June 2018 to May 2019 in the Vestmannaeyjar archipelago (Westman Islands). Song and social calls were identified in the recordings. The JASCO acoustic detector was tested and performed to assess humpback whale seasonality in the area. The second aim of this project, it is to prove the hypothesis that similar songs are sung contemporarily in two different areas of the North Atlantic: in the Westman Islands (Southern Iceland), and out of Vesterålen (Northern Norway). This hypothesis is based on a recent study about the humpback whale migratory route from Norway to West Indies. The song recorded in south Iceland was delineated. Random Forest analysis and Markov chain model analysis were performed to assess the reliance of the Icelandic song transcription. Song comparison was carried out with recordings made in February 2019 from the LoVe observatory archive in the Norwegian waters. The Random Forest, Levenshtein distance and Dice index were performed to assess the song similarity and shared repertoires. Results show that humpback whales are present in the south of Iceland for the entire period of the acoustic monitoring, apart for April. They use the area during summer as feeding grounds and during winter as a presumable stepover during migration. Moreover, the song comparison between Norway and Iceland showed values higher of 0.60 of Levenshtein Similarity Index between same phrase types and an overall Dice’s Similarity Index of 58% between the two songs. This provides additional evidence of singing activity in subarctic feeding grounds and add further information to the North Atlantic humpback whale populations structure, migration patterns, and song exchange opportunities.