Meeting Abstract
Sea turtles and salmon are iconic long-distance migrants in which the young travel along vast, population-specific routes through the open sea, unassisted by older conspecifics. How such animals complete their first migration, sometimes crossing an entire ocean basin before returning, has long intrigued biologists. Experiments have revealed that loggerhead sea turtles (Caretta caretta) from eastern Florida begin their migration with a ‘magnetic map’ in which regional magnetic fields function as navigational markers and elicit changes in swimming direction at crucial locations along their trans-Atlantic migratory route. The direction of swimming elicited by each field appears to be suitable for helping turtles remain within the warm-water currents of the North Atlantic subtropical gyre and advance along the migratory pathway. Similar responses have been found in juvenile Chinook salmon (Oncorhynchus tshawytscha), which respond to fields like those at the latitudinal extremes of their Pacific Ocean range by orienting in directions that would, in each case, lead toward their marine feeding grounds. In both turtles and salmon, the magnetic map that guides juvenile animals appears to be inherited, inasmuch as regional magnetic fields elicit orientation responses in individuals that have never migrated or even been in the ocean. The existence of similar magnetic navigation strategies in young salmon and sea turtles suggest that this mechanism is phylogenetically widespread and may explain how diverse marine animals complete long, complex journeys through the sea despite lacking migratory experience.
