Long-Distance Animal Migrations in the Oceanic Environment: Orientation and Navigation Correlates

A large variety of marine animals migrate in the oceanic environment, sometimes aiming at specific targets such as oceanic islands or offshore productive areas. Thanks to recent technological developments, various techniques are available to track marine migrants, even when they move in remote or inhospitable areas. The paper reviews the main findings obtained by tracking marine animals during migratory travels extending over large distances, with a special attention to the orientation and navigation aspects of these phenomena. Long-distance movements have now been recorded in many marine vertebrates, revealing astonishing performances such as individual fidelity to specific sites and basin-wide movements directed towards these locations. Seabirds cover the longest distances, sometimes undertaking interhemispheric flights, but transoceanic migrations are also the rule in pelagic fish, turtles, pinnipeds, and whales. Some features of these journeys call for the involvement of efficient orientation and navigational abilities, but little evidence is available in this respect. Oceanic migrants most likely rely on biological compasses to maintain a direction in the open sea, and displacement experiments have provided evidence for an ability of seabirds and turtles to rely on position-fixing mechanisms, possibly involving magnetic and/or olfactory cues, although simpler navigational systems are not to be excluded.