Arctic humpback whales respond to nutritional opportunities before migration

Abstract

Rapid climate change in Arctic and Subarctic ecosystems is altering the spatio-temporal dynamics and abundance of resources. Whether highly mobile predators can respond and match their movements to changed resource peaks remains largely unclear. In the last decade, humpback whales (Megaptera novaeangliae) established a new foraging site in fjords of northern Norway during the winter, outside of their presumed foraging season. We used photographic matching to show that whales first sighted during fall in the Barents Sea foraged in northern Norway from late October to February, staying for up to three months and showing high inter-annual return rates (up to 82%). The number of identified whales increased steadily from 2010 to 2016. Genetic sexing and hormone profiling in both areas suggest higher proportions of pregnancy and a female bias in Norwegian waters. This indicates that the new site may be particularly important for pregnant females, likely to improve body condition before migration. Our results suggest that baleen whales can respond to nutritional opportunities along their migration pathways, in some cases by extending their feeding season. This supports the idea that migrating marine mammals can access novel prey resources as part of their response to environmental changes.

Characterizing movement and searching behavior of humpback whales along the North-Norwegian coast

“…In the last decade, large masses of Norwegian spring-spawning (NSS-) herring (Clupea harengus L.) have aggregated in specific fjord systems in Troms, Northern Norway in winter, followed by hundreds of humpback and killer whales (Orcinus orca) (3,10,17,18). These areas are located close to one of the assumed migration routes of humpbacks to and from the Barents Sea summer feeding grounds, and the wintertime feeding may therefore represent a stop-over to re-fuel before they later migrate to the southern breeding grounds in the (14,19).This occurrence of whales near the coast and populated areas enabled us the unique opportunity to study their detailed behavior (3,(20)(21)(22).…”