Alternative migration strategies of fin whales in the Mediterranean sea : evidence of a lunar influence

Understanding migrational behavior of fin whales (Balaenoptera physalus) in the Mediterranean basin is of greatest importance in terms of research on cetaceans, but also in terms of conservation for a specie considered as ‘endangered’ based on the IUCN Red List criteria. We investigate in this study the migrational behavior of several individuals from this population. Several datasets (telemetry-tracking, satellite-estimated chlorophyll concentration and oceanic currents) are used to assess their long- and short-term behavioral adaptations to diverse biomes. We highlight the fact that meeting points with the North Atlantic population exist at strategical environmental locations. We prove that migrating fin whales show distinct swimming behaviors depending on the lunar phases by comparing their daily distances swam to the tortuosity of their paths. These distinct behaviors might be due to prey availability as well as acting as a temporal trigger to maximize chances of reproduction success. Indeed, this migration strategies of the Mediterranean population is also explained by reproductive constraints of an isolated population susceptible to inbreeding. We then focus the study on two fin whale paths in the Strait of Sicily showing that they are able to communicate between each others, adapt their foraging area to instantaneous moon-driven changes of oceanic conditions but also to follow cyclic seasonal variations of resources availability. We finally bring a new insight on an alternative pattern for migration strategies of fin whales in the Mediterranean sea.