Investigating the feeding effort of humpback whales in sub-arctic Iceland by integrating fine-scale sensor data and land-based observations

• Main Author: Jóhanna Sigurðardóttir 1994-
• Other Authors: Háskóli Íslands
• Format: Master Thesis
• Language: English
• Published: 2023
• Subjects: Líffræði; Arctic; Eyjafjörður; Iceland; Megaptera novaeangliae; North Atlantic
• Online Access: http://hdl.handle.net/1946/44627

Icelandic waters are among the important productive feeding grounds for humpback whales (Megaptera novaeangliae) in the North Atlantic, primarily during the feeding season from spring to fall. In recent years, there has been an increasing occurrence of wintering whales off Iceland. This study aimed to examine the foraging behavior of humpback whales in different seasons. Breathing records from land stations were employed, ensuring no disturbance to the whales’ behavior. The results indicated that humpback whales by Iceland exhibit peak feeding activity towards the end of the feeding season, right before migration, highlighting the significance of this period which might be vital for migration and mating success. Further, data from an archival digital tag that was placed on an overwintering whale in a shallow area in Eyjafjörður was used to examine the correlation between surface and deep dive parameters. The results showed that the number of breaths in surface bouts indicated the depth and duration of deep dives, and the respiration rate positively correlated with the lunge rate. Additionally, data on the foraging activity of humpback whales in the literature were compared over seasons, with the results indicating more foraging activity of humpback whales in the northern hemisphere compared to the southern hemisphere in autumn. The overwintering whale in Eyjafjörður did not show distinct foraging behavior compared to humpback whales in other seasons. A comparison of the tag data with simultaneously collected land-based data revealed some limitations to the land-based methods which allows for improvements of this method for future land-based monitoring of whales. The rapidly changing climate influences the prey distribution this apex predator utilizes. Long-term monitoring of humpback whales from land stations might provide information into their adaptive foraging strategies in response to these changes.