North Atlantic Blue and Fin Whales Suspend Their Spring Migration to Forage in Middle Latitudes: Building up Energy Reserves for the Journey?

Abstract

The need to balance energy reserves during migration is a critical factor for most long-distance migrants and an important determinant of migratory strategies in birds, insects and land mammals. Large baleen whales migrate annually between foraging and breeding sites, crossing vast ocean areas where food is seldom abundant. How whales respond to the demands and constraints of such long migrations remains unknown. We applied a behaviour discriminating hierarchical state-space model to the satellite tracking data of 12 fin whales and 3 blue whales tagged off the Azores, to investigate their movements, behaviour (transiting and area-restricted search, ARS) and daily activity cycles during the spring migration. Fin and blue whales remained at middle latitudes for prolonged periods, spending most of their time there in ARS behaviour. While near the Azores, fin whale ARS behaviour occurred within a restricted area, with a high degree of overlap among whales. There were noticeable behavioural differences along the migratory pathway of fin whales tracked to higher latitudes: ARS occurred only in the Azores and north of 56°N, whereas in between these areas whales travelled at higher overall speeds while maintaining a nearly direct trajectory. This suggests fin whales may alternate periods of active migration with periods of extended use of specific habitats along the migratory route. ARS behaviour in blue whales occurred over a much wider area as whales slowly progressed northwards. The tracks of these whales terminated still at middle latitudes, before any behavioural switch was detected. Fin whales exhibited behavioural-specific diel rhythms in swimming speed but these varied significantly between geographic areas, possibly due to differences in the day-night cycle across areas. Finally, we show a link between fin whales seen in the Azores and those summering in eastern Greenland-western Iceland along a migratory corridor located in central Atlantic waters.

Linking pollutant exposure of humpback whales breeding in the Indian Ocean to their feeding habits and feeding areas off Antarctica

“…Humpback whales wintering in the southwestern Indian Ocean are presumed to feed mainly in Feeding Area III as confirmed by recent satellite tagging (Cerchio et al, 2013;Fossette et al, 2014). During their north-and southbound migration and on the breeding grounds, humpback whales, like most baleen whales, feed at a reduced rate and opportunistically (Cerchio et al, 2013;Fossette et al, 2014;Silva et al, 2013). The extensive fat accumulated during the summer feeding season in Antarctica support their reproduction and their migratory journeys (Silva et al, 2013).…”

“…During their north-and southbound migration and on the breeding grounds, humpback whales, like most baleen whales, feed at a reduced rate and opportunistically (Cerchio et al, 2013;Fossette et al, 2014;Silva et al, 2013). The extensive fat accumulated during the summer feeding season in Antarctica support their reproduction and their migratory journeys (Silva et al, 2013). However, whales, and marine mammals in general, experience a high risk of accumulating toxic levels of highly lipophilic chemicals because of their metabolic requirements, extensive fat store and long life span (Bossart, 2011).…”

Underwater Ambient Noise in a Baleen Whale Migratory Habitat Off the Azores

“…The areas around Condor and Açores seamounts are frequently used by blue and fin whales for foraging (Silva et al, 2013 and by sei whales for migrating . Gigante seamount is close to a transit area for the three species, and occasional feeding may also occur there.…”

“…Blue and fin (B. physalus) whales interrupt their journeys to northern latitudes to feed in the archipelago every spring and early summer (Silva et al, 2013. Sei whales (B. borealis) travel through the archipelago in spring on their way up to the Labrador Sea but they do not seem to forage routinely in the area .…”

First record of a live blue whale (Balaenoptera musculus) in the Iberian Peninsula after three decades

“…Most of the whales sighted in winter and spring off the Azores and Canary Islands migrate north along the mid-Atlantic ridge to Iceland, while others probably migrate along the European coast, around Ireland to either Iceland or Norway (Sears & Perrin 2009, Silva et al 2013. The observed whale probably belongs to this second group of coastal migrants, as Charif & Clark (2009) suggest that most individuals detected acoustically between September and January in the British Islands were migrating to the south or southwest, and on their journey to southern areas they are supposed to migrate around Madeira islands, where blue whales were watched in September in different years (Freitas et al 2012).…”