Patterns in the Acoustic Presence and Vocal Behaviour of Bowhead Whales Balaena mysticetus in Eastern Fram Strait

• Main Author: Hiemer, Katharina
• Format: Thesis
• Language: unknown
• Published: 2019
• Subjects: Arctic; Greenland; Svalbard; Balaena mysticetus; Fram Strait; Spitsbergen
• Online Access: https://epic.awi.de/id/eprint/52042/; https://hdl.handle.net/10013/epic.3c3fefbb-d3bd-4fd7-85f0-183ff4db443f

Fram Strait, located between Greenland and Svalbard, provides a critical habitat to seasonally migrant and endemic cetaceans, including bowhead whales Balaena mysticetus of the Spitsbergen population. This population has been depleted close to the point of extinction by commercial whaling and still is considered as endangered. Due to its low abundance and the remoteness of its habitat, baseline knowledge on spatio-temporal distribution patterns and behavioural aspects are scarce, yet crucial for the conservation of this population. Long-term passive acoustic recordings were collected at different locations in eastern Fram Strait (78-79°N, 0-7°E), contributing to the Ocean Observing System FRAM (Frontiers in Arctic Marine Monitoring). Data recorded during two sampling periods between 2012 and 2017 were analysed for the occurrence of bowhead whales using the Low-Frequency Detection and Classification System (LFDCS). Seasonal changes in their acoustic repertoire were investigated using recordings from a single year and location. Bowhead whales were acoustically present from autumn throughout winter (October/November-February) and occasionally in spring (March-June), suggesting that Fram Strait is used as an overwintering area. Given that peak levels of acoustic presence coincided with the presumed mating period of bowhead whales, Fram Strait may also serve as a mating area. No bowhead whales were recorded in summer (July-September), indicating that they either were vocally inactive or had migrated to summering areas. Eight distinct song types of bowhead whales were identified comprising simple songs and call sequences. Even though more than one song type was recorded at a given time, there was an overall trend that songs occurred in temporal succession. It remains speculative why songs appeared and subsequently disappeared with the progressing season, but the temporal succession possibly is related to the song types being used in different behavioural contexts. One song type formed an exception as it was recorded ...