BEHAVIORAL PROCESSES AND MECHANISMS UNDERLYING MAGNETIC NAVIGATION IN SEA TURTLES

Diverse marine migrants travel long distances to specific oceanic foraging sites, but how animals navigate to these locations, and recognize them upon arrival, has remained enigmatic. Numerous animals, including sea turtles, use the natural variations in Earth’s magnetic field as a magnetic map to aid in navigation. Thus, one possibility is that animals learn the unique ‘magnetic coordinates’ of a foraging site and use this information to return. To investigate this, I developed a new technique in which turtles were conditioned to associate the magnetic coordinates of geographic areas with food, demonstrating for the first time that an animal can learn the magnetic field of a specific location. The conditioning technique was subsequently leveraged to investigate other aspects of turtle magnetic sensing, including: (1) the resolution and sensitivity of the magnetic map sense; (2) whether turtles average magnetic field information over time instead of taking instantaneous readings; and (3) the mechanism underlying the magnetic map sense. I then used a second behavioral assay to investigate whether the magnetic compass (or directional sense) of turtles relies on chemical reactions involving pairs of radicals, as has been hypothesized. In a final study, I investigated embryonic turtle responses to local magnetic fields, as a means of understanding when turtles begin to respond to magnetic field information. Overall, the results significantly advance our understanding of magnetic navigation and magnetoreception in sea turtles and other animals.