Fin whale movement patterns from the Mediterranean sea reveal summer habitat use in the North Atlantic and potential feeding behavior

Abstract Understanding the movements of highly mobile marine species is essential for identifying critical habitats and developing effective conservation measures. Although occasional movements of fin whales ( Balaenoptera physalus ) between the Mediterranean Sea and the North Atlantic Ocean have been reported, the extent to which these movements represent a recurrent component of Mediterranean fin whale ecology remains unclear. Here, we present satellite telemetry tracks from seven fin whales (2022–2025) with five years of supporting evidence from systematic land-based observations (2021–2025) in the western Ibiza Channel to investigate movement patterns, behavior, and habitat use beyond the North-Western Mediterranean Sea. All tracked whales left the Mediterranean Sea passing through the Strait of Gibraltar and subsequently moved northward along the Atlantic coast of the Iberian Peninsula, providing direct evidence of cross-basin movements from the Mediterranean to the North Atlantic. Behavioral analyses using two independent movement-modeling approaches identified a common pattern of directed transit followed by area-restricted search (ARS) behavior—commonly associated with foraging—in several Atlantic areas, including waters off the Iberian Peninsula and the Bay of Biscay. The occurrence of prolonged ARS behavior in these areas is consistent with the use of Atlantic feeding habitats. The similarity of movement trajectories across individuals, years, tagging locations, and data streams indicates that seasonal use of Atlantic waters may represent a regular component of the movement ecology of at least some fin whales in the Mediterranean Sea. Given that these movements span multiple jurisdictions and areas of intense maritime activity, conservation measures should consider both important feeding habitats and the migratory routes that connect them.