Seasonal trends and diel patterns of downsweep and SEP calls in Chilean blue whales

• Published in: Journal of Marine Science and Engineering
• Main Authors: Redaelli, Laura, Mangia Woods, Sari, Landea Briones, Rafaela, Sayigh, Laela S.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: MDPI 2022
• Subjects: Chilean blue whales; marine bioacoustics; Balaenoptera musculus chilensis; Chile; D calls; SEP calls; diel patterns; seasonal trends; marine conservation; Austral; Balaenoptera musculus; Blue whale
• Online Access: https://hdl.handle.net/1912/29051

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Redaelli, L., Mangia Woods, S., Landea, R., & Sayigh, L. Seasonal trends and diel patterns of downsweep and SEP calls in Chilean blue whales. Journal of Marine Science and Engineering, 10(3), (2022): 316, https://doi.org/10.3390/jmse10030316. To learn more about the occurrence and behaviour of a recently discovered population of blue whales, passive acoustic data were collected between January 2012 and April 2013 in the Chiloense ecoregion of southern Chile. Automatic detectors and manual auditing were used to detect blue whale songs (SEP calls) and D calls, which were then analysed to gain insights into temporal calling patterns. We found that D call rates were extremely low during winter (June–August) but gradually increased in spring and summer, decreasing again later during fall. SEP calls were absent for most winter and spring months (July–November) but increased in summer and fall, peaking between March and April. Thus, our results support previous studies documenting the austral summer residency of blue whales in this region, while suggesting that some individuals stay longer, highlighting the importance of this area as a blue whale habitat. We also investigated the daily occurrence of each call type and found that D calls occurred more frequently during dusk and night hours compared to dawn and day periods, whereas SEP calls did not show any significant diel patterns. Overall, these findings help to understand the occurrence and behaviour of endangered Chilean blue whales, enhancing our ability to develop conservation strategies in this important Southern Hemisphere habitat. Financial support for expeditions, deployments, and retrievals of MARUs, and for some of the data analysis, was provided by Fundacion MERI, Av. Pdte. Kennedy 5682, Vitacure, Región Metropolitana, Chile. The data analysis for this study was carried out without external funding.